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A study of the pressure stability of calcium stearate-cetane systems containing additives

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A study of the pressure stability of calcium stearate-cetane systems containing additives

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Content A STUDY OP THE PRESSURE STABILITY OP
CALCIUM STEARATE-CETANE SYSTEMS CONTAINING ADDITIVES
A Thesis
Presented to
the Faculty of the Department of Chemistry
The University of Southern California
In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Chemistry
by
Richard James Coswell
June 19^9
UMI Number: EP41596
All rights reserved
INFORMATION TO ALL USERS
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UMI EP41596
Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author.
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c ’S 3 . . C 8 ¥ X
This thesis, w ritten by
Richard _ James .Coswell.
under the guidance of h.X$... Faculty Committee,
and approved by a ll its members, has been
presented to and accepted by the Council on
Graduate Study and Research in p a rtial fu lfill
ment of the requirements fo r the degree of
Master of Science
........ Jtaooi.S., ..Bogardus
D ean
D a te ...... ...................
F a c u lty C om m ittee
C hairm an
| v'\ve.f— v s > t-A V-V
300
Vue>. I
v o 3>
ACKNOWLEDGEMENT
The writer wishes to acknowledge the guidance and
encouragement of Dr. Robert D. Void, which made this
thesis possible.
TABLE OF CONTENTS
CHAPTER PACE
I. INTRODUCTION ................................... 1
Statement of the problem................. 1
Literature survey .......................... 1
Experimental techniques ................... 3
Definition of terms ....................... 6
II. MATERIALS AND APPARATUS ........................ 9
Materials ......................... . 9
Calcium stearate .......................... 9
Cetane.................................... 10
Additives ................................ 10
Miscellaneous materials . . . ............ 10
Apparatus.................................... 14-
Oven ...................................... 14-
Pressure stability apparatus ............. 15
Other apparatus . ....................... 19
III. EXPERIMENTAL TECHNIQUES........................ 20
Preparation of samples..................... 20
Determination of pressure stability .......... 21
Other techniques............................ 22
IV. RESULTS......................................... 24-
Visual observations.......................... 24-
X-ray diffraction patterns ............... 4-5
iv
CHAPTER PAGE '
Pressure stability .......................... 65
Syneresis of anhydrous calcium stearate-
cetane systems.......... 130
Refractive index of gel liquid ............. 132
V. DISCUSSION OF THE VISUAL OBSERVATIONS ..... 134 '
VI. INTERPRETATION OF THE X-RAY DIFFRACTION '
PATTERNS............ l4l
Calcium stearate-cetane......................l4l
Calcium stearate-stearic acid . ...........143
General discussion of results with
CaStrg-HStr systems ..................... 151
Calcium stearate-methanol-cetane ........ 154
Calcium stearate-water-Monoplex ........... 155
Calcium stearate-n-heptanol ............... 155
Lithium stearate-cetane......................156
VII. POSSIBLE INTERPRETATIONS OF VISUAL AND X-RAY
OBSERVATIONS.................................. 159
Silica-water, glass wool-water, and
"coated'* silica-cetane as examples of
solid-liquid systems ................... 160
Possible factors in addition to particle
form in the prevention of syneresis of
calcium stearate-cetane systems ........ 162
CHAPTER PACE
Particle-particle interaction ............. 162
Liquid-particle interaction ................ 164
One possible role of additives in prevent
ing syneresis.............................. 165
IVIII. CORRELATION OF PRESSURE STABILITY RESULTS
WITH POSSIBLE GEL STRUCTURES................. 171
Geometrical considerations ............... 171
Effect of preparative conditions on pressure
stability...................................173
Composition dependence of pressure
stability.................................. 17^
Effect of time of standing on pressure
stability ... 1 ............................ 175
Effect of additive content on pressure
stability . . . ..........................175
Pressure stability of lithium stearate-
cetane systems ......................177
Pressure stability of commercial
greases.....................................178
General considerations of pressure
stability results ......................... 185
BIBLIOGRAPHY ............................................ 189
LIST OP TABLES
.TABLE PAGE
I. Additives to CaSt^-Cetane Systems .... 11
II. Characteristics of Commercial Greases . . . 13
III. Precision as a Function of Heating Time . . 77
IV. Precision vs. Total Liquid Loss CaStr2~
H20-Cetane Systems (10 psi)............. 79 !
V. Effect of Slow Crystallization of Cetane
on Pressure Stability of 18$ CaStr2~
0.5$ H20-Cetane Systems................. 8l
I
VI. Effect of Soap Content on Pressure
Stability of CaStrg-^O-Cetane Systems
(10 p s i ) ................................ 84
VII. Effect of Water Content on Pressure
Stability of 18$ CaSt^-^O-Getane
Systems (10 p s i ) ....................... 87
VIII. Effect of Stearic Acid on Pressure Stability
of 18$ CaStrg-HStr-Cetane Systems (10 psi) 89
IX. Effect of Methanol on Pressure Stability of
18$ CaStrg-MeOH-Cetane Systems (10 psi) . 92
X. Effect of Oil on Pressure Stability of
18$ CaStrg-0.5$ H2O-OH Systems
(10 p s i ) ................................ 94
XI. Effect of Pressure on Pressure Stability
vii
TABLE PAGE
of Calcium Stearate-Additive-Cetane
Systems.................................. 97
XII. Effect of Aging on Pressure Stability of
18$ CaStr2-0.5$ H20-Cetane Systems
(10 psi) .............................. 100
XIII. Comparison of results of Accelerated
Syneresis Tests with Six Month Syneresis
from Data of Farrington and Humphreys . . 103
XIV. Effect of Temperature of Quenching on
Pressure Stability of 18$ GaStrg-
0.5$ H20-Cetane Systems (10 psi) .... 105
XV. Density of Pressed and Unpressed Cakes . . 110
XVI. Final Per cent Soap Calculated for
CaStr2-H20-Cetane Systems (10 psi) . . . 113
XVII. Final Per cent Soap Calculated for
18$ CaStrg-HgO-Getane Systems (10 psi). . 114
XVIII. Final Per cent Soap Calculated for
18$ CaStrg-HStr-Getane Systems (10 psi) . 115
XIX. Final Per cent Soap Calculated for
18$ CaStr2-Methanol-Cetane Systems
(10 p s i ) . 116
XX. Final Per cent Soap Calculated for
18$ CaStr2-015$ Water-Oil Systems
viii
TABLE PAGE
(10 psi) ....................... 117
XXI. Final Per cent Soap Calculated for
CaStr2-Additive-Cetane Systems ........ 118
XXII. Pressure Stability of Lithium Stearate-
Cetane Systems .......................... 122
XXIII. Thermal Treatment of Lithium Stearate-
Cetane Systems................. 123
XXIV. Pressure Stability of Commercial Grease
Systems.................................. 126
XXV. Liquid Loss from Anhydrous CaStr2-
Cetane Systems ......................... 131
XXVI. Refractive Indices of Expressed Gel
Liquid.................................. 133
XXVII. Short Spacings of CaStr2 #1 and CaStr2-
HStr Systems of Various Treatments . . . 145
XXVIII. Principal Short Spacings of HStr Forms . . 147
XXIX. X-Ray Spacings of LiStr-Cetane Systems . . 157
FIGURE
LIST OF FIGURES
PAGE
1. O v e n ................................ .... 16
2. Pressure Stability Apparatus . . 7 . . . . . 17
3.
CaStr2-Cetane, H-147 ............... .... 47
4. CaStr2-HStr-Cetane, M-49 ........... .... 48
5.
CaStr2-HStr-Cetane, M-50 ........... .... 49
6. 0aStr2-Me0H-Cetaiae, S - 4 0 ........... .... 50
7.
CaStr2-MeOH-Cetane, C-2 ............. .... 51
8. Gastr2-MeOH-Cetane S-41............. . . . . 52
9.
Gastr2-HStr, M-56 ...................
. . . . 53
10. Castr2 and HStr, M - 4 3 ........ . .... 54
11. GaStr2 and HStr, M-47 ............... .... 55
12. CaStr2-HStr, M-42 .................... .... 56
13.
CaStr2-HStr, M-51 ................... .... 57
14. Gastr2-HStr, C-l ................... .... 58
15.
Neofat 1-65, RDV x-1 ............... .... 59
16. Neofat 1-65, RDV x-2 ............... . . . . 60
17. Stearic Acid RDV x-3 ............... . . . . 61
18. CaStr2-H20-Monoplex, C-3 ........... . . . . 62
19.
CaStr2-n-heptanol, C-4 ............. . . . . 63
20. LiStr-Cetane, M-55 ................. . . . . 64
21. t/s vs. t for Sample E-22 ........... . . . . 68
22. t/s vs. t for Sample D-40 ........... .... 70
4*
X
FIGURE PAGE
23. Per cent Loss vs. Composition for Lata
of Table VI . . .......... 85
V
24. Per cent Loss vs. Water Content for Lata
of Table V I I .............................. 88
25- Per cent Loss vs. HStr Content for Lata
of Table VIII.............................. 9©
26. Per cent Loss vs. MeOH Content for Lata
of Table IX .............................. 93
27. l/a vs. Six Month Syneresis Loss from Lata
of Farrington and Humphreys............... 102
28. Appearances of Pressed Cakes ............... 108
29. Evaporation of Liquid from CaStr2-di-
(n-butyl) amine ............................ 121
30. Results of Filter Paper Test with Commercial
Greases.................................... 128
31. Comparison of Pressure Stability and Filter
Paper Test Results....................... 180
32. t vs. s for Commercial Greases............. 184
33. Possible Pressure Stability Behavior of
Commercial Greases ....................... 186
CHAPTER I
INTRODUCTION
Statement of the problem. It is the purpose of this
investigation to examine representative soap-oil systems to
determine (l) factors influencing the formation of non-
syneretic gels of those systems and (2) the structure of
the gels themselves if possible. 1
The system chosen for the most intensive study was
calcium stearate-cetane. Calcium stearate was chosen
because (l) it is readily prepared in a pure, or very near
ly pure, form, and (2) investigations on the phase behavior
of calcium stearate and calcium stearate-oil systems were
in concurrent progress in these Laboratories (29, 30).
Cetane, n-hexadecane, was chosen because (1) it is a pure
hydrocarbon representative of paraffinic constituents of
commercial hydrocarbon oils, (2) it is readily available in
a pure form, and (3) it is inert chemically toward soaps
and is geometrically similar toward the stearate ion, both
factors probably simplifying its interaction with the soap.
Literature survey. The literature available concern
ing the systems of interest is not extensive and not always
reliable with respect to interpretation.
The nature and use properties of commercial calcium
soap-oil systems, greases, are well known from the
2
practical standpoint; such information is summarized in the
volume by Klemgard (18) and an article by Boner (4).
Farrington and Davis (10) have studied the fiber nature of
calcium greases ultramicroscopically, and recently Birdsall
and Farrington (3) have studied calcium greases with the
electron microscope.
Observations about the nature of pure calcium soap-
oil systems were made by McBain and McClatchie (21), who
observed that anhydrous calcium palmitate-xylene systems
formed syneretic gels. Lawrence (20) records his observa
tions of the gelling ability of a number of soaps in Nujol.
Gallay and Puddington (12, 13) have examined the sedimenta
tion volume, viscosity, stream double refraction, and
surface tension of calcium stearate in commercial oils in
the presence of certain additives. They interpreted their
results in terras of agglomeration of suspended soap par
ticles and the effect of the additive in rendering the soap
particles lyophilic. Hoppler (17) investigated the role of
water in systems of calcium oleate-oil and concluded that
water is necessary for fiber formation, and demonstrated
the existence of a hydrate of calcium oleate. Recently a
phase rule investigation of calcium stearate and calcium
stearate-cetane has been undertaken by Void and Void (30)*
The existence of a hydrate of calcium stearate has been
I I
; demonstrated (29). j
I j
J In general, however, examination of the available j
i j
i t
i literature only reveals a lack of knowledge concerning the
i
J structure of gels of calcium soap-oil systems and the
I
I dependence of the gel properties (rheology, fibrous char-
i acter, tendency toward syneresis) on the physical chemical
t
I nature of the soap-oil systems.
I
j
: )
1 Experimental techniques. The experimental tech-
■ i
niques were chosen keeping in mind the twofold purpose of
t
I the investigation and the time available for the study. j
{ Visual and tactual observations of the systems over 1
i I
' a considerable temperature range were relied upon to supply|
i t
j information concerning gross changes in the nature of the ! '
systems. Temperatures at which large changes in physical
sta^te of the systems occurred could be easily determined
i
and correlated to some extent with X-ray and calorimetric j
! !
! data obtained at the same time in this Laboratory. The
i
: appearance of the systems could also be related to the
' other properties which were, studied.
The X-ray powder method, whose utility in the case of
! soap-oil systems has already been demonstrated (30)# was
! ’
j used to relate the macroscopic, behavior with the molecular
| structure of' the systems, Insofar as it could be deduced
i
I from the patterns. Of particular interest was the relation
4 ,
between crystallinity and liquid loss from the systems.
Since the nature of the gel structure was also to
be investigated, the measurement of some physical property ,
of the gel was undertaken. Consideration of the methods
currently available for the study of gel structure led to
the elimination of a majority of them as inapplicable to
the present type of system.
Methods of testing the properties of commercial
greases were also considered, but again most had to be dis
carded, generally because of the excessive amounts of
sample required for a single test or because of the indef
inite nature of the quantity measured. After consideration
of all the factors, or possible factors, which are involved,
the method finally settled upon was the determination of
the liquid retentive properties of the gel systems.
The basis of the method lies in the effect the gel
structure will have on the amount of liquid which can be
forced out of the gel. In soap-oil gels, liquid may be
held (l) by simple capillary forces, in which liquid is
held in narrow spaces between solid particles, (2) as
lyosphere or adsorbed liquid, although it may be doubted at
present whether this mechanism contributes significantly i
i
to liquid retention in these systems, and (3) dissolved in
solid soap, in which the oil may be held by strong inter-
5
molecular forces.
It would probably be a relatively easy matter to
decide between mechanism (l) or (3) as the principal cause
of stability against liquid loss. The liquid loss method
to be described, however, would not be capable of revealing
such a mechanism as (2) as distinct from one or the other
of the other two.
An accelerated syneresis test devised by Herschel
(l6), used by Farrington and Humphreys (11) in studies of
greases, and later modified by Doscher (7) for his investi
gation of sodium stearate-cetane-water systems was the
original serious consideration for the study of non-
syneretic systems in the present investigation.
The apparatus used by the above authors consisted
essentially of a metal plunger in a block. The sample was
contained between mats of filter paper. The plunger rested
on the top mat, thus pressing liquid out of the grease into
the filter paper. The method was considered at a disadvan
tage in the case of very soft systems, which would suffer
excessive deformation and might even be forced around the
sides of the plunger, thus invalidating the results.
The present apparatus utilizes a shortened porous
Alundum thimble to hold the sample and provide the filter
membrane. External pressure is supplied by means of an
6
oxygen tank, thus allowing a closely controlled pressure
to be maintained for any desired period. The thimble is
held in a metal cylinder with specially fitted, detachable
ends.
The quantity of liquid expressed under given condi
tions, the rate of expression, and the composition of the
expressed liquid can be measured by the present method.
Indeed, one great advantage of the present apparatus lies
in the ability to identify expressed liquid.
Farrington and Humphreys (11) attempted to relate
their results on greases to the syneresis of their systems
over an extended period. They found that the best correla
tion was between the initial rate of loss determined by
their apparatus and the quantity of oil leaking from the
system over, an extended period.
Definition of terms. It is necessary to clarify the
terms relating to the liquid retentive abilities of the
systems in question in order to avoid confusion during the
discussions which follow. Of necessity, there will be a
certain arbitrariness in the explanation of the terms, but
a clear distinction between terms can best be made by
strict definition.
Syneresis is the spontaneous exudation of liquid
from a gel. The liquid is expressed from the gel structure,
7
leaving a gel or solid mass of diminished volume. The
term, syneresis, refers neither to the rate nor to the
extent to which the process occurs. Such quantities are
completely expressed oniy as numbers accompanied by a des
cription of the system and methods of determination of
syneresis. However, when used in the present discussion,
syneresis will refer merely to the presence of syneretic
liquid.
The phrase, stability of a gel, will be used to
refer to the ability of a gel to resist loss of its liquid
by any process, evaporation excluded. It is an ambiguous
term unless accompanied by specifications as to whether
liquid is lost by syneresis, or whether an applied force
causes separation of the liquid phase. A qualitative
description of stability is sometimes possible, e.g., "The
system underwent extensive syneresis," indicates a low gel
stability with respect to syneresis, regardless of the
behavior of other systems, related or not, in this respect.
Both rate and total loss are bound up in such a statement.
However, when reference is made to stability with respect
to syneresis, it is understood that this term as used in
this report will refer to the extent of syneresis.
The term, syneretic tendency, will be used to imply
rate of syneresis or time required for first appearance of
8
syneretic liquid after gel formation.
The term, pressure stability, refers to the ability
of a gel to retain its liquid against an externally applied
force acting to cause separation of liquid from gel. No
number used in the present study expresses the pressure
stability as an absolute property of any system, since the
experimental method and conditions employed will affect
the numerical results. It should be pointed out, to avoid
later confusion, that the pressure stability of two samples
does not involve a direct comparison of the quantities of
liquid expressed from the two systems, but rather an
inverse comparison. That is, of two systems, the one
losing the smaller amount of liquid has the greater pres
sure stability. The pressure stability refers exclusively
to the quantity of liquid expressed after a given period
of time on application of a given pressure. The pressure
stability does not refer in any way to the rate at which
liquid is expressed from a system, although it is possible
that the rate may be related to the pressure stability.
CHAPTER II
MATERIALS AND APPARATUS
A. MATERIALS
Calcium stearate. The calcium stearate used in this
investigation was prepared by Hattiangdi and is described
by him (15)- This product was known as CaStr2 #5* It was
dried at 110° C.* to constant weight for use in the prepara
tion of samples.
However, the #4 CaStr2 preparation was used for a
few initial experiments. The #4 preparation was made in
the same manner as the #5 soap, and from Neo-fat 1-65, a
product of Armour and Co., which had also been used to
prepare the #5 soap. However, despite the similarity in
preparative conditions, the two preparations differed in
their X-ray diffraction behavior. The #4 soap reverted to
an anhydrous pattern on drying at 110°. This behavior was
in contrast to that of the #5 soap, which retained its
hydrate pattern on drying at 110°. The difference in
behavior in this respect has been discussed by Void (30)-
Despite the difference in the two preparations, their
pressure stability behavior was the same. Both required
* All temperatures used in this thesis are in °C.
water to form a non-syneretic grease.
10
Cetane. The cetane used was the du* Pont product
purified by Grandine and used in an investigation of cal
cium stearate-cetane systems (28).
Additives. The effect of additives on the observed
properties of calcium stearate-cetane systems was studied.
The additives and brief, identifying statements are sum
marized in Table I.
Miscellaneous materials. A number of other soap-oil
systems were studied for comparative purposes, and a few
other materials were used during the course of the study
for a variety of reasons.
Metasap Chemical Co. technical lithium stearate was
used to prepare a few systems. Titration of the dried soap
in ethanol with standard base indicated one to two per cent
free fatty acid on a weight basis.
Medicinal Nujol and E.X. practical grade decalin
(decahydronaphthalene) were used as solvents in addition to
cetane.
Some commercial greases were examined for liquid
loss. Their characteristics are summarized in Table II,
although a study of their thermal and X-ray behavior has
also been made (31).
11
TABLE I
ADDITIVES TO CaStr2-CETANE SYSTEMS
Additive Characteristics
Water
Stearic Acid
Methanol
Acetone
a-tetralone
Nitroethane
Pyridine
n-heptanol
di-n-butylamine
De-ionized
Re-crystallized twice from
aeetonitrile; designated as 5R3
(28)
B. & A. Reagent Grade, fresh bottle
carefully capped
99.5$ U.S.P., C.P., dried over
K2C03 and distilled. B.P. 56.5°
Synthesized in Organic Chemistry
Lb., Univ. of So. Calif, by
Friedal-Crafts condensation of
benzene and succinic anhydride,
followed by Clemmenson reduction,
treatment with S02C12, and finally
ring closure with AlClo. Product
distilled at 95-100° at 1 mm.
pressure. Reddish color.
Commercial Solvents Corp. N. Y.
product, kept in carefully
stoppered bottle
E. K. Karl Fischer reagent grade,
kept in carefully stoppered, brown
bottle
E. K. reagent grade, received from
R. D. Void, used by Leggett
Paragon Testing Laboratories product,
catalog number 5033> kept in
carefully stoppered bottle
Calcium acetate
monohydrate
B. & A. Reagent Grade
12
TABLE I (continued)
ADDITIVES TO CaStr2-CETANE SYSTEMS
Additive Characteristics
Nitrobenzene Paragon Testing Laboratories
product, redistilled, first cut
discarded
di-(2-ethylhexyl) Resinous & Chemical Products, Inc.
sebacate product
Diethylene glycol Carbide and Carbon Chemicals Corp.
product, 0.3$ water maximum when
supplied, kept in carefully
stoppered bottle
Methyl Stearate Obtained from R. D. Void, product
from which HStr A obtained on
hydrolysis
Amyl acetate B. & A. Reagent Grade, kept in
carefully stoppered bottle
TABLE II
CHARACTERISTICS OP COMMERCIAL GREASES
Grease Soap
Cation
$ Soap Fatty acid Oil Additives
California Research Al-2 A1 12 60$ HP al
40$ HStr
@ 100°P.
350 SSU
"Trace"
h2o
Unoba-A2 Union Oil Ba 18 I.V.45
Tallow
100°P.
604 SSU
0.01$ H20
0.5$ "oxid,
inhibitor"
3.7$ HAc
California Research Ca-1 Ca 18 30$ HPal;
20$ HStr;
50$ HOI
@ 100°F.
320 SSU
"Trace"
H20
Shell Li Multipurpose Li 10 (?) HStr
12-hydroxy
@ 100°P.
108 cs.
v.i. 56
none
California Research Na-1 Na 16 50$ HPal;-
40$ HStr;
10$ HOI
@ 100°F.
420 SSU
none
Battenfeld AN-G-3A Li 10 (?) HStr
H
OO
14
Some unrelated systems were prepared to demonstrate
the feasibility of a particle size effect in gel formation.
Two types of silica were used for this purpose. One silica
was Fisher Scientific Co. 240 mesh silica. The othdr
silica was a sample from the Linde Air Products Co. of
their "Linde Coated Silica 30," a specially treated silica
wettable by hydrocarbons. The manufacturer has not seen
fit to disclose the method of its preparation. Bentone 18,
a bentonite clay marketed by the National Lead Co. and
prepared by the adsorption of long chain amines or quater
nary salts on the clay particle, was also used for the
preparation of a solid-liquid system.
B. APPARATUS
Oven. Heating of samples whose behavior on heating
was to be observed was carried out in an oven designed for
the purpose. All systems whose liquid loss was determined
were heated in this oven.
The oven was made from two concentric tin cans in
which windows, front and back, had been cut and the tops
removed. Both cans were wrapped with l/l6 inch asbestos
paper. Number 22 Chromel resistance wire was mounted on
two 1/8 inch thick transite boards, each the size of one
side of the inner can, and wrapped tightly around the inner
15
can, leaving only windows and the top not covered by wire.
; The space between inner and outer cans was filled with
asbestos wool, except for the spaces between windows. A
rotating sample holder projected through the center of the
can. The oven was completed by a completely removable
transite lid, reinforced with asbestos paper and layers of■;
transite which fitted down into the inner can. The current{
. through the heating coil was controlled by a 5 amp-* 120
volt Variac. A diagram of the oven is shown in Figure 1.
i Heating rates of one to two degrees per minute could be
achieved.
The thermometer used to record all temperatures was
designated as RJC I. It gave readings of 100° with boiling,
water vapor at J60 mm. and 185-I860 as the melting point of;
succinic acid (188° com.) without stem corrections. The
thermometer projected down about one-third of the way into
the oven, with its stem projecting above the lid at the 80°:
mark.
Pressure stability apparatus. The principles on
; which the apparatus to determine liquid loss are based have
. already been outlined. The design of the apparatus used is;
shown in Figure 2.
s
The cylinder was made from a piece of cast iron pipe, 1
. six inches long and one inch outside diameter. The pipe i
16
TRANSITE LID
TO VARIAC
2 -4" WATCH
GLASSES PER
WINDOW TO
COVER 3“ WINDOW
STIRRER
30*- NO.22 CHR5MEL
WRAPPED AROUND CAN
ASBESTOS WOOL
FIGURE 1
OVEN
GAS PRESSURE
Jill J DU]
niiimi
ALUNOUM THIMBLE
FIGURE 2
PRESSURE STABILITY APPARATUS
\ was threaded at both ends to take caps. Both caps were j
! drilled to take short nozzles, 1/4 inch in diameter. A ,
i piece of special pressure tubing was attached to the nozzle
i at the top by a hose clamp and was connected to the pres- j
r
i sure tank through a regulating valve. The nozzle at the j
i other end provided the pressure drop to atmospheric pres-
i
f sure and allowed the issuing liquid to be caught easily.
| A tight fitting rubber stopper was used to provide
I a tight seal at the top cap, while an annulus of rubber
i
| . sheeting served as a washer at the bottom. The washer
i
1 swelled somewhat initially, but after cutting the swollen I
j t
► washer to the right size, it served quite satisfactorily, i
I ' !
! and there was no excessive air leak. 1
The threads of the bottom cap were carefully greasedi
I
to minimize air leaks, care being taken to avoid over- j
j greasing so that grease would not get on the thimbles. !
1 ■ i
j A total of four thimbles were used, all being Alun- j
I ;
\ dum medium porosity filters. The thimbles were 22 mm. '
: ' i
| inside diamter, 5 ram* inside depth, and held 1.4 to 1.9 j
1 grams of sample. Before filling, the thimbles were care- ,
! fully washed several times with carbon tetrachloride and •
i !
I dried at 110° overnight. An average gain in weight of 0.2 j
i
to 0.4 mg. following successive cleaning operations was
generally observed with all thimbles. Twice during the
19
course of the study, the thimbles were rinsed briefly with
concentrated hydrochloric acid and flamed over a Fisher
burner. The thimbles appeared to suffer no deterioration
in mass or loss of porosity, reverting to their original
weight.
Other apparatus. All other apparatus used in the
study is well-known or is described elsewhere. X-ray
diffraction patterns were made using the North American
Philips Spectrometer. The instrument and technique for
use with soap-oil systems are described by Void and Void
(30). Expressed liquid was characterized refractometri-
cally using an Abbe refractometer.
CHAPTER I I I
EXPERIMENTAL TECHNIQUES
A. PREPARATION OP SAMPLES
Samples of systems were prepared for one or both of
two purposes: (l) for visual observations only, or (2) for
the determination of liquid loss.
When prepared for the former purpose, there were no
specifications as to size of tube or weight of sample.
Systems of this type generally weighed from one to two
grams.
The systems prepared for the second purpose, however,
were carefully controlled with respect to preparative con
ditions. The sample tubes were pyrex tubing 15 mm. inside
diameter and about 10 cm. long when sealed. The tubes were
washed with dichromate cleaning solution, rinsed repeatedly
with de-ionized water, and dried for at least 24 hours at
110°. They were flamed prior to the weighing operations,
corked, and allowed to cool before weighing.
The tubes were kept corked during the weighing as
much as possible. The weighing operations consisted of
introducing dried soap, any additive, and cetane in that
order and weighing by difference. The cetane was intro
duced by means of a long medicine dropper. Precaution was
taken not to get materials on the upper walls, where the
tubes were sealed without evacuation. The time required
: for weighing and sealing was generally twenty to thirty
minutes. In every case the total weight of system (soap,
oil, and additive) was 5*0 grams.
The sealed tubes were heated to the desired tempera
ture in the oven. The samples for liquid loss determina
tions were maintained at the desired temperature for one
hour and then cooled in the desired manner. Standard pro-
1 cedure for nearly all systems, except where specific pre
parative conditions were studied, consisted in maintaining
the sample at 155° for one hour and quenching the system in
dry ice-alcohol.
B. DETERMINATION OF PRESSURE STABILITY
Following quenching of the sample, enough time was
allowed to elapse so that the sample could warm up to room
temperature (about fifteen to thirty minutes). The tube
was then cracked open, the contents removed onto a clean
watch glass, and worked with a spatula for three to five
minutes. The thimbles were filled by lightly pressing the
sample into the thimble with a spatula. Several strokes
were required to completely fill the thimble. The top of
the sample was smoothed with the spatula.
22
The five gram sample provided enough material to fill
two thimbles, which were weighed, placed in the pressure
cylinder alternately, and subjected to gas pressure,
generally 10 pounds per square inch (psi), for varied
lengths of time. The thimbles were removed from time to
time and weighed, note being made of the total length of
time the samples had been subjected to pressure. Applica- j
tion of pressure for 60 to 100 minutes was sufficient to
provide the necessary data for calculation of results, with ;
six to eight weighings recorded. After sufficient data
from one run had been obtained, the residue was carefully
removed from the thimble with a spatula and the inside of
the thimble carefully wiped with a cloth dampened with
carbon tetrachloride, and the thimble weighed.
C. OTHER TECHNIQUES
The X-ray diffraction patterns were obtained by
methods discussed by Grandine (14) and Void and Void (30).
The preparation of samples was not all done by one person, ;
M. J. Void and G. S. Hattiangdi also contributing time to
this end. The techniques were the same, however, except for
the ever-present personal factor. The instrument settings
:were: X-ray slides and Geiger tube slides both 3, X-ray slit
and Geiger tube slit both medium, amplitude and damping
23
both 1.
The extent of syneresis of some anhydrous systems
was studied in an attempt to ascertain the feasibility and
usefulness of such measurements and also to gain some idea
of the quantity of liquid which could be extracted from
such systems. One gram samples of the anhydrous systems
were prepared in pyrex tubes 9 mm. inside diameter and 8 cm.,
long. The tubes were heated to 280°, held there one hour,
and quenched in dry ice-alcohol. The tubes were allowed
to stand for one week unopened, after which they were
opened, and as much of the syneretic liquid that could be
poured into tared weighing bottles was done so. Rolls of
Whatman #1 filter paper were then inserted into the resi
dues and all possible remaining liquid was soaked up after
four days.
The commercial greases were subjected to a modifica
tion of the "filter paper test" well known in the grease
industry (l8). Small brass rings, 13.2 mm. in diameter and:
20 mm. in height, were completely filled with the grease.
The rings were then placed on pieces of 11 cm. Whatman #1
filter paper, and the oil allowed to soak into the filter
paper. The tests were run simultaneously to make condi
tions as nearly alike as possible. Marks of the advance
of the oil ring were made from time to time.
CHAPTER I V
RESULTS
A. VISUAL OBSERVATIONS
Both the simple two component and the additive three
component systems were observed visually over a tempera
ture range. The tactual nature at room temperature was
also observed in some cases. The description of all sys
tems examined is outlined in the following tables. The
observations are grouped for the convenience of comparison.
The quenching temperature was 155° except where specifi
cally noted.
Visual observations of anhydrous calcium stearate-
cetane systems.
f o Soap
(by weight Temp. Observations
of system)
5.1 115 Some swelling of solid, plenty of free
liquid
120 Solid now stiff, clearing, still a
large amount of free liquid
140 Stiff part flowing, dispersion into
liquid beginning
170 Soap and oil pretty well mixed
25 Faintly greenish to transmitted light,
immediate and extensive syneresis
after quenching from 280°
10.5 113 Swelling of solid, thickening of
entire system
25
Visual observations of anhydrous calcium stearate-
cetane systems (continued).
< ? o Soap
(by weight Temp. Observations
of system)
117 Clearing at edges starts"
125 Clearing complete
135 Stiff mass now able to flow, viscosity
decreases slightly as temperature
rises
25 Translucent, syneretic gel after
quenching from 280°
14.9 114 Thickening of system
116 Clearing starting
120 Stiff mass almost completely clear
140 Stiff mass observed to flow
25 Syneretic, translucent gel after
quenching from 280°
19.0 115 Thickening, clearing
120 Clearing almost complete
145 Flowing observed
25 Syneretic, translucent gel after
quenching from 280°
24.0 115 Thickening, clearing
120 Clearing almost complete
160 First signs of flowing
25 Somewhat translucent, syneretic gel
on quenching from 280°
30.0 118 Thickening with clearing
125 Clearing virtually complete
150 Flowing Just evident
25 Syneretic, somewhat translucent gel
on quenching
35-0 115 Thickening
116 Clearing starts
125 Clearing complete
170 Flowing Just starting
Somewhat translucent, syneretic gel
on quenching from 280°
25
26
Visual observations of anhydrous calcium stearate-
cetane systems (continued).
% Soap
(by weight Temp. Observations
of system)
39*0 118 Thickening and clearing starts
130 Clearing almost complete
150 First signs of flowing
25 Semi-translucent, syneretic gel after
quenbhing from 280°
*1-4.6 130 Clearing and thickening
150 Clearing complete
190 Flowing just now noticeable
25 Semi-translucent, syneretic gel after
quenching from 280°
Both before and after the removal of syneretic and
loosely held liquid, the systems often had a grainy feel.
This feel was quite marked in the concentrated systems, but
extended well down into dilute soap concentrations also.
No systematic endeavor was made to allow the systems
to cool slowly. The dilute soap systems when cooled slowly,
however, generally formed a white, mushy solid. The tem
perature at which solid appeared was not that corresponding
to any change on heating; undercooling by 10-20° from the
temperature of clearing was observed in some cases. On
reheating, however, the material followed almost exactly
its original heating behavior.
Visual observations of calcium stearate-water-cetane
systems.
% Soap % Water
(by weight
of system)
18.0 0.10
18.0 0.25
18.0 0.40
18.0 0.54
18.0 0.75
Temp. Observations
120 Thickening, followed by some
clearing
128 Very thick, stiff mass
132 Slight flowing
137 Solid completely dispersed to
translucent, very viscous
material
155 Mass fluid, but still very
sluggish
25 After quenching, a translucent,
somewhat mushy material
resulted. On working, it had
the appearance of applesauce
120 Heavy thickening
128 Clearing to very viscous mass
with some suspended lumps
135 Viscosity slowly decreasing,
less than anhydrous but still :
much greater than monohydrate
systems
25 Soft, whitish, non-syneretic
material on quenching
120 Swelling
123 Clearing to fairly fluid solution
25 White, opaque, non-syneretic
mass on quenching |
115 Slight thickening
120 Definite thickening and clearing ,
125 Clearing complete to fluid
solution
25 Firm, white, opaque, non-syner
etic ;mass on quenching
125 Clearing to fluid solution after
swelling .
25 Non-syneretic, opaque, white !
i
!
28
Visual observations of calcium stearate-water-cetane
systems (continued).
% Soap f o Water
(by weight Temp,
of system)
Observations
18.0 1.0
18.0
7-5
10.0 0.3
12.8 0.38
24.9
30.0
0.75
0.90
L.
mass on quenching 1
r
130 Swelling of solid :
131 Solution of solid under way j
155 Small drop of water appears to
be at bottom of fluid solution J
25 White, opaque, non-syneretic :
system after quenching I
120 Clearing '
125 Solution complete, droplets of
water on walls of tube, but ;
not in liquid, which is quite j
fluid
25 Firm, white, non-syneretic mass
with droplets of liquid on ;
upper walls of tube
120 Clearing to very fluid solution 1
25 Very soft, opaque, white mass; ;
"wet” appearance, but no |
syneresis, oily feel
120 Clearing to fluid solution ^
starting l
25 Very soft, opaque, white mass; j
"wet”appearance, but no j
syneresis, oily feel
1
I
125 Clearing to fluid solution |
25 Firm, opaque, non-syneretic mass;:
very slightly "wet" appearance,;
greasy feel |
126 Thickening and clearing to fluid i
solution; viscosity of hydrous
systems increasing as soap 1
content increases, but systems ;
still much more fluid than i
29
Visual observations of calcium stearate-water-cetane
systems (continued)
$ Soap $ Water
(by weight Temp
of system)
38.4 1.15
45.0 1.35
25
128
25
125
25
Observations
corresponding anhydrous
systems
Very firm, opaque, non-syneretic
mass, greasy
Clearing.to solution, relatively
fluid for so much soap,
solution process occurs over
about a 10° range
Very firm, opaque mass, slightly
sticky in addition to greasy
feel
Clearing around edges but no
particular signs of solution;
clearing proceeds slowly over
a temperature range; it is
necessary to heat the mixture
to 195° for nearly one hour
to achieve a complete
homogeneity
Extremely firm, crumbly, gummy,
not at all greasy mass on
quenching from 155°
With the exception of most of.the 18$ calcium
stearate systems, the ratio of moles of soap to moles of
water in the foregoing systems was one. Three per cent
water on the basis of weight of soap corresponds to an
equimolar ratio.
On slowly cooling the dilute hydrate systems (10$
and 18$ soap), a white powder suspended in liquid or soft
30
white mush were generally observed. Undercooling in these
systems was also notable. Solid soap often appeared 10° to
15° below the temperature of clearing when the systems were
allowed to cool slowly in the oven. However, on standing
for one hour at 115 , an 18$ calcium stearate-0.5$ water-
cetane system was observed to contain solid soap which had
evidently separated during the hour. It was possible to
keep an 18$ calcium stearate-0.5$ water-cetane system at
120° for one hour without separation of solid.
Visual observations of calcium stearate-ste&ric
acid-cetane systems.
$ Soap $ Acid
(by weight
of system)
18.0
0.51
18.0 1.0
Mol acid Temp.
Mol soap
0.06 126
128
140
0.12
25
122
126
Observations
Milkiness, then thicken*
ing
Clearing over a 10°
range
Solution is rather vis
cous, but fluid enough
to flow from one end
of the tube to the
other
Nearly transparent, some
what syneretic gel on
quenching
Possible slight lighten
ing to milkier mixture
Clearing to fluid solu
tion, solid lumps
appear to swell and
become translucent
before going into
31
Visual observations of calcium stearate-stearic
acid-cetane systems (continued).
f o Soap f o Acid
(by weight
of system)
18.0. 2.0
18.0 3.0
18.0 4.0
18.0 5.0
18.0 6.0
Mol acid Temp.
Mol soap
25
0.24 • 123
25
0.36 125
25
0.48 122
25
0.60 120
25
0.72 125
Observations
solution
Very slightly syneretic,
translucent gel ;
I
Milkiness followed by
almost direct solution
to very fluid solution
in 5°
Firm, slightly trans
lucent non-syneretic
mass
Milkiness followed by
clearing over a 5°
range to a very fluid,
isotropic solution
Somewhat soft, white,
opaque, non-syneretic
mass
Milkiness followed by
clearing to very fluid
solution :
Very soft, oily feeling, :
wet appearing, but non-
syneretic mass on ,
quenching
Solution starts to take ;
place, practically
complete at 125° to
very fluid solution
Puree-like mass, very
wet appearing, but no
distinct syneresis
Clearing to isotropic,
fluid solution under
way
32
Visual observations of calcium stearate-stearic
acid-cetane systems (continued)
Soap % Acid
(by weight Mol acid
of system) Mol soap
18.0 7.0 0.84
Temp. Observations
25 Very soft, non-syneretic,
opaque mass
120 Clearing perceptible,
almost complete over
an g° range
25 Soft, non-syneretic,
opaque mass
A most striking observation with this set of samples
was the sharp increase in softness as the stearic acid con
tent increased beyond two per cent acid. The soft systems
immediately after their formation could hardly be described
as gels; many of them were incapable of retaining any sort
of molded form. It is worthy of further note that when the
systems which were soft on formation were allowed to stand
in air for a few days, they became noticeably harder.
Birdsall and Farrington (3) also made the same observation
with respect to stearic acid-stabilized greases.
33
Visual observations of calcium stearate-methanol-
cetane systems.
% Soap % MeOH
(by weight Mol MeOH
of system) Mol soap
18.0 0.48 0.48
18.0 1.0 0.95
18.0 1.5 1.6
18.0 2.0 2.1
18.0 2.65 2.8
Observations
Thickening and clearing
to relatively fluid
solution over a 10°
range
Somewhat translucent,
mushy, but non-synere^-
tic gel on quenching
Solid gradually disap
pearing into a fluid
solution, solution
more fluid than the
one above
White, opaque, non-
syneretic mass, soft
Thickening and clearing
over a 10° range to
fluid, isotropic
solution
White, opaque, non-
syneretic mass, rather
soft, "wet" appearance
Thickening, clearing to
a fluid solution in
10°
Soft, "wet" appearing,
white opaque mass, no
definite syneresis
Thickening and clearing
to fluid solution
starting
Very soft, mushy, "wet"
appearing mass on;-
quenching, no synere
sis of the type en
countered in
Temp
119
25
115
25
120
25
118
25
120
25
34
Visual observations of calcium stearate-methanol-
cetane systems (continued).
% Soap % MeOH
(by weight Mol MeOH Temp,
of system) Mol soap
Observations
18.0 3-14
18.0 4.0
3.3
4.2
anhydrous systems
116 Clearing and thickening
start, fluid solution
after 10°
25 Very soft, mushy, "wet"
opaque mass on
quenching
120 Thickening and clearing
to fluid, isotropic
solution
25 White, opaque, fluid
like material which
could be poured into
thimbles. Very "wet"
appearance, but no
definitely free liquid
in the sense of a
syneretic process,
more like a milky
suspension
Again, as with the systems of calcium stearate-
stearic acid-cetane, the nature of the quenched systems
appears to change markedly on reaching a certain concentra
tion of the additive. In the case of the methanol systems,
this concentration is at 1.5% methanol in an 18$ calcium
stearate-eetane system. The soft systems of the methanol
set, however, behaved differently compared to the stearic
35
acid systems, which were soft but hardened on standing.
No hardening was observed in any case when the methanol
systems were allowed to stand for several days. The very
soft systems appeared to separate free liquid with the
appearance of a powdery, white, flocculated precipitate on
standing several days at room temperature.
containing a variety of additives were prepared to examine
the behavior of such systems and to determine, if possible,
the nature of the materials which exert a stabilizing
influence on the systems with respect to syneresis, visual
observations being used as the criterion. A summary of the
visual observations of such systems follows.
Visual observations of calcium stearate-cetane-
miscellaneous additive systems.
Composition Temp. Observations
18. CaStr2 125 Thickening to a stiff mass
A number of systems of calcium stearate and cetane
2.0 MeStr
80.0$ Cetane
142 Some flowing, but material
is still very viscous
150 Fluidity increased, greater
than non-additive systems,
but very much less than
hydrate systems
25 Translucent, syneretic gel
on quenching
17.5£' CaStr2
71.0$ Cetane
11.5$ Nitrobenzene 120 Clearing beginning
130 Clearing complete, but mass
110 Sticking of solid to walls,
thickening
Visual observations of calcium stearate-cetane-
miscellaneous additive
Composition
17-9$
2.2% Nitrobenzene
79*9$ Cetane
18.0%
2.3$ Amyl Acetate
79*7$ Cetane
18.0% CaStr2
2.6$ Di-(2-ethylhexy1)
Sebacate
79.4$ Cetane
9.50$ CaStr2
2.72$ Acetone
87.9$ Cetane
systems (continued).
Temp. Observations
is still heterogeneous
150 Stiff mass at walls slowly :
mixing with liquid over
a temperature range of
about 20°
25 Translucent, syneretic gel j
on quenching '
118 Thickening to a stiff mass,
clearing starting at one
end
135 Clearing complete, sugges
tion of some flowing of
mass
25 Translucent, syneretic mass
on quenching
115 Thickening and clearing
underway
130 Clearing pretty well
complete
140 Some signs of flowing of
system
25 Translucent, syneretic mass ,
on quenching
118 Thickening and cleaning over
about a 15° range
140 Signs of flowing of mass
evident
25 Translucent, syneretic mass
on quenching
115 Solution clearing and incor
porating solid to give a
uniform fluid solution
which appears to be
isotropic
25 White, opaque mass on
quenching, no syneresis
immediately evident, on
37
Visual observations of calcium stearate-cetane-
miscellaneous additive systems (continued).
Composition Temp. Observations
8.83$ CaStr2 113
6.35$ a-tetralone 120
SH-,8% Cetane
25
18.0$ CaStrg 105
2.1 % Nitro'efhane
79.9^ Cetane 108
112
115
155
25
18.Og CaStr2 105
2.0$ n-heptanol 110
80.0$ Cetane
25
18.0% CaStr2 108
2.0$ Di-(n-butylamine)
80.0$ Cetane
25
standing overnight,
couple of drops of liquid
flow from mass on
inversion
Clearing starting i
Completely clear, isotropic,
fluid solution, reddish
Magenta colored, non-
syneretic, opaque mass on
quenching
Possible milkiness replac
ing coarse suspension
Thickening
Clearing at edges
Clearing definitely in
progress to stiff mass
with some solid still
undissolved
At end of one hour, mixture
has become fluid and amber
Opaque, tan, non-syneretic
mass on quenching
Clearing starting
Clearing virtually complete '
to fluid, isotropic
solution
Firm, opaque, non-syneretic
mass on quenching
Clearing starting to fluid
solution, which is
achieved in about 10° ,
Firm, opaque, non-syneretic
mass on quenching
38
Visual observations of calcium stearate-cetane-
miscellaneous additive systems
Composition Temp.
17.8# CaStro 110
2.5f o Diethylene glycol
79-7^ Cetane 130
25
17.2$ CaStrP 103
11.5$ Pyridine
71.2$ Cetane
108
112
25
18.1# CaStr2 110
2.3$ Pyridine
79.6$ Cetane
25
17.7$ CaStro 120
5-1$ CaAc2-H20 135
77-3$ Cetane
150
l60-
165
(continued).
Observations
Clearing of soap with
thickening
Solution of soap virtually
complete, fluid
Rather soft, opaque, non-
syneretic mass on
quenching
Signs of clearing at edges;
some solid sticking to
glass and clearing
Solid clearing, solution
taking place, liquid
clear and quite mobile
Solution virtually complete
Non-syneretic, opaque mass
on quenching
Clearing, temporary thick
ening, followed by
solution at 115°
Somewhat translucent, but
non-syneretic mass on
quenching; some syneresis
after standing three days
Stiffening but no clearing
Opacity disappearing,
material beginning to
‘ become somewhat translu
cent, flow in evidence,
material appears striated
with opaque "strings" in
translucent or near trans
lucent, stiff mass
Viscosity decreases as
temperature rises, still
some undissolved solid,
probably calcium acetate
Bubbling quite evident
39
Visual observations of calcium stearate-cetane-
miscellaneous additive systems (continued).
Composition Tfemp. Observations
172 Material appears to stiffen,
on standing at 172,
material becomes very
stiff; large number of
small bubbles through
system 1
240 Material still stiff 1
155 Mass still stiff on stand
ing at 155° for one-half
hour
25 Sticky, dry appearing mass
on quenching, could be
worked to fairly smooth
grease with some sticki
ness
The observations above are quite striking, and their
possible significance will be commented upon later.
In addition to systems in which cetane was the sol
vent, several calcium stearate systems were prepared in
which other liquids were used as the dispersion medium.
Some of the systems were simple two component systems,
while others contained an additive in addition to the soap
and oil. The two types are grouped separately below.
Visual observations of calcium stearate-liquid
systems.
40
Composition
17.55& CaStr
0.5$ H20 ^
8l.8^ Decalin
1 8 .0 # C aS tr2
0.5$ HoO
81.556 Nujol
17.956 CaStro
0 .6^ h2o
81.5# Di-(2-ethylhexyl)
Sebacate
18.0$ CaStr?
82.0$ Di-(2-ethylhexyl)
Sebacate
Temp. Observations
115 Slight thickening and
swelling
120 Signs of clearing
123 Clearing very sharp, very
fluid solution results
25 Opaque, soft, white mass
with slight yellowish
tinge, strong odor of
decalin, non-syneretic
130 Swelling and clearing of
mixture
132 Solution definitely under
way over a 15° range to
a somewhat viscous
solution
25 Very smooth, colorless,
semi-translucent, non-
syneretic grease on
quenching
110 Mixture appears to be
smoother, fewer lumps of
solid noticed
120 Translucence of some
particles
124 Sudden definite clearing to
fluid solution,yellowish
25 Tan, opaque, non-syneretic
mass
120 Thickening and swelling
122 Clearing starting
130 Clearing well underway to
a very stiff mass
25 Somewhat translucent, mushy
appearing mass on
quenching, syneretic
41
Visual observations of calcium stearate-liquid
systems (continued).
Composition
17.5# CaStr2
82.5$ n-heptanol
17.5# CaStr2
82.5$ Diethylene
Glycol
18.0# CaStr2
82.0$ Di-(n-butyl)
Amine
Temp,
100
25
108
25
103
110
25
Observations
Immediate solution to very
fluid solution
Very firm, non-syneretic
mass, dry appearance
Clearing of soap to very
stiff, translucent mass; !
diethylene glycol appears
to exert no solvent action
toward soap; no appre
ciable solvent action,
even at 240° for one-half
hour
Mushy mass, inhomogeneous,
when quenched from 240°
Swelling and clearing
Solution almost complete,
very fluid
Firm, dry appearance on
quenching
A number of calcium stearate-stearic acid systems
were prepared in order to investigate the possibility of
compound formation or altered crystal habit in soap-oil
mixtures containing stearic acid. X-ray patterns of the
soap-acid mixtures served as an aid in the interpretation
of patterns of soap-acid-oil systems. Visual observations
were made in the course of the preparation of the systems
and are recorded below. The #5 preparation of calcium
stearate was used in the preparation of all systems, and
42
the 5R3 stearic acid was used for all systems except the
one in which the ratio of moles of acid to moles of soap
was two. In that instance the acid used was Neo-fat 1-65
from the same lot used to prepare the #5 calcium stearate.
Visual observations of calcium stearate-stearic
acid systems.
Moles Soap
Moles Acid Temp. Observations
3.74 100 Translucent anisotropic particles on
sides of tube
100- Gradual increase in extent of translu-
150 cency
175
Flowing perceptible
25
Quenched from 155°, glassy particles
1.99
90 Some Indications of translucent spots
95
Definite translucence
150 Some flowing of mass, definite aniso
tropy, fluidity increases slightly as
temperature rises
25
Glassy particles on quenching from 155°
1.0 100 Translucent particles
120 Flowing evident, but mass is anisotropic
solid still present
200 Anisotropic material considerably fluid
25
Somewhat amber, opaque material on
quenching
7.4 115
Translucent spots visible
150 Entire mass translucent, no marked
anisotropy, mass very stiff
210 Mass still not flowing
25
Glassy material on quenching from 155°
0.435 75
Material sticking to sides of wall
95
Swelling to translucent lumps
99
Solution beginning, partially complete
In 5° range
110 Further solution taking place
43
Visual observations of calcium stearate-stearic
acid systems (continued).
Moles Soap
Moles Acid Temp.
130
25
Observations
Solution still taking place, complete
after about 10°, solution is rather
viscous
Opaque, brick-like mass on quenching
In addition to calcium stearate systems, a few sys
tems were prepared in which lithium stearate was the soap,
Both cetane and decalin were used as the solvents. The
observations follow.
Visual observations of miscellaneous soap-oil
systems.
Composition
18.0# LiStr
82.0$ Cetane
18.0# LiStr
82.0$ Decalin
Temp.
195
180
175
25
175-
180
185
155
Observations
No clearing or swelling until this
temperature; suspension starting
to clear with slight increase in
viscosity; solution starts and
occurs in 10° range; deep tan
solution, quite fluid
On oven cooling, viscosity increas
es markedly on cooling so that
flowing ceased at l80°
Separation of solid from solution
Deep tan, greasy, firm mass on
quenching from 155°
Clearing with no thickening
Solution complete, fluid, amber
After cooling and standing here,
thickening occurred to a highly
anisotropic jelly-like material
which became less translucent
Visual observations of miscellaneous soap-oil
44
systems (continued).
Composition Temp. Observations
after further standing
25 Semi-translucent tan, firm mass on
quenching, strong odor of
decalin, no syneresis
General remarks coneerning visual observations. The
rate of heating in making the visual observations was of
the order of two degrees per minute. Superheating of
samples could conceivably have occurred, but when and to
what extent it occurred is not known. However, at such
heating rates superheating may not have been serious.
The fact that heating was continuous during a trans
formation makes it uncertain whether the transformation
would have completed itself at the same temperature at
which it started. Thus, observations of the temperature
range required to bring about complete clearing may be due
to this cause rather than the fact that the transformation
itself actually required a range of temperature to come
about.
It is doubtful that the temperatures at which flow
ing of very stiff systems was first observed is of great
significance. Such an observation can be expected to be
dependent upon external experimental conditions, such as
45
the angle at which the tube was being rotated.
Despite the possible uncertainties in the tempera
ture of transformation, the entire set of data are useful
since the amount of error in temperatures will probably be
of the order of 5-10° at most. Correlation with calori-
metric data where available (27, 28) indicates that obser
vations in the calcium stearate-cetane systems are actually
quite good, considering that different preparations of
calcium stearate were used for each study (Arnis prepara
tion for the calorimetric study (27), #5 for the visual
observations), since it has been found that the thermal
behavior of different calcium stearate preparations varies
considerably (29).
Of further usefulness are the observations of the
relative fluidity of the various systems. Such comparisons
can be made in a qualitative sense because differences were
generally quite marked in different types of systems. The
meaning of the differences in the observed viscosity cannot
rightfully be deduced without quantitative data, although
the observations above are suggestive.
B. X-RAY DIFFRACTION PATTERNS
X-ray diffraction patterns of representative systems
were obtained and were conveniently recorded here by a
{ five-fold reduction of the original strip chart pattern.
! A satisfactory description of each system and the observed
, spacings accompany each pattern. Other X-ray data cited
| in the discussion will be referred to the appropriate
I reference where similar pantograph reductions and data
; i
exist. i
The pantograph reductions follow as Figures 3 to 20 j
inclusive on pages 47 to 64 inclusive.
H-147 47"
i
FIGURE 3
CaStr2-CETANE
Initially 44.6# CaStrg #5, 55.4# cetane, heated ' <
to 280° for one-half hour, quenched in dry ice-'
alcohol, allowed to stand one week in sealed
tube and one week in open tube. Syneretic
liquid poured off and remainder soaked up with
filter paper. Final composition 63.0# CaStr2.
Corr. Half width
Obs. 20 d/n _I 1/32 degrees
5*32 16.40 6 0.19
0.6
8.83 9.94 3
0.10
0.65
12.60
6.99 3
0.10 0.6
19.10 H 4.65 13
0.4 3.4
20.85
4.26 32 1.0
2.3
22.39 3.97 31 0.97 1.9
37.02
2.43 2 0.06 0.4
38.47 .2.34 2 0.06
0.85
40.34 2.23 2 0.06 1.4
Long spacing
n
3
5
7
Av.:
d
49.20
49.68
48.91
49.26
M-49
FIGURE 4
CaS tr--HS tr-CETANE
Coswell sample E-42-1. 17.5# CaStro, 2.1#
HStr, remainder cetane. Heated to I55°»
held one hour, quenched In dry ice-alcohol.
Corr. Half width
Obs. 29 d/n I
1/43
degrees
5.15 16.93 7
0.16 0.52
6.90 12.68 2 0.05
1.00
8.50 10.32
3 0.07 0.53
18.96 H 4.66
43
1.00 6.14
21.26
4.17 17
0.40 0.80
23.5 (s) 3.77 3
Halo:
34-48 2.6- 2
0.05
36.0
2.49
2 0.05 0.50
38.2
2.35
2
0.05
1.00
40.5
2.22 1 0.02 1.70
42.7
2.11 2
0.05
1.40
Long spacing
n
3
4
5
Av.:
50.79
50.72
51.60
51. $
20=50° M-50 49
FIGURE 5
CaStr2-HStr-CETANE
Coswell sample E-42-ii. 18.0# CaStr^, 5-9#
HStr, remainder cetane. Heated to 155°>
held one hour, quenched in dry ice-alcohol,
run immediately.
Corr. Half width
Obs. 20 d/n _I 1/44 degrees
5.15 16.93
4
0.09 O.65
6.90 12.68 ? 2 0.05 0.90
8.55
10.26
3 0.07
0.80
18.96 H 4.66 44 1.00 6.30
21.19 4.18 20 0.45 0.90
23.5 (s) 3.77
Present
Halo:
34-48 2.6-
3 0.07
35.9 2.5
2 0.05 0.70
40.4
2.23
2 0.05
1.20
43.0 2.10 1 0.02 0.50
Long spacing
n
3
4
5
Av.:
50.79
50.72
51.3
5TAT
'20= 2°
S-40
50
FIGURE 6
CaStrg-MeOH-CETANE
CaStr2 5R3AH, dried to constant weight
(17.W , MeOH (analytical), (1.1#), and
cetane. Held at 130° for two hours;
quenched in dry ice-alcohol.
Corr. Half width
Obs. 20 d/n _I 1/41 degrees
5.18 16.83
6 0.15
O.56
6.54 13.37 3 0.07
0.22
8.33 ? 10.53
8.84
9.93 5
0.12 0.67
9.86 8.91 3
0.12 0.32
19.0 H 4.66 41 1.00 4.8
19.56 4.52 6 0.15
0.74
21.23 4.17 33
0.80 1.2
22.54 (s) 3.93
23.55 (s) 3.77
Long spacing
n d Possible d
3
50 .49
> - - ' .
4
53.48
5
49.63 52.65
6
53.44
Av • •
50.06 53.T9
29=2
C-2
51
FIGURE 7
CaS tr2-MeOH-CETANE
18.0# CaStro #5, 1.0# MeOH, cetane. Heated
to 155°> held there one hour, quenched in
dry ice-alcohol. Run immediately.
Obs. 20
Corr.
d/n _I 1/32
Half width
degrees 29
5.22
16.71
8
0.25 0.57
7.00 12.50
3
0.10 0.80
8.72 10.06
3
0.10 1.10
12.20 7.21 2 0.06
0.85
19.0 H
4.67 32 1.0 5.0
19.5 4.55 5
0.16 0.70
20.12 4.41 12 0.38 0.80
21.29 4.17 17 0.53
0.90
22.68 3.92
3
0.10 0.60
25.69 3.47
2 0.06
1.5
30.13 2.97 3
0.10
0.37
35.97 2.50 2 0.06
Long spacing
n d
3 50.13
4 50.00
5 50.30
7 50 Al
Av.: 50.22
20=50° S-41 52
FIGURE 8
CaS tr2-MeOH-CETANE
Calcium stearate (5R3AH dried to constant
weight), 15.0# methanol (analytical), 2.8$;
cetane. Heated at 130° for two hours;
quenched in dry ice-alcohol.
Corr. Half width
Obs. 20 d/n _I
1/53
degrees
5.20
16.77
6 0.11 0.86
6.94
12.61
3
0.06 0.34
7.83 ? 11.19
2 0.04 0.38
8.80
9.97 3
0.06 1.00
9.80 ? 8.96
3
0.08 0.94
12.57
7.00 4 0.08 0.20
19.0 H 4.66
53
1.00 5.2
20.0 4.42 10 0.19
0.8
21.27 4.16 30
0.57
1.1
23.90
3.71 3
0.0 6 0.6
Long spacing
n d
3 50.31
4 50.44
5 49.85
Av.: 50.20
20=2
I
I
I
I
♦
t
FIGURE 9
CaStr AND HStr
Coswell sample E-45. 1 mole CaStrp to 1/8
mole HStr. Heated to 210°, cooled to 155°
held there one hour, quenched In dry ice-
alcohol.
t
Half width
1/39 degrees 2Q
Corr
d/n Obs. 2©
0.65
1.30
16.67
10.08
4.22
5.23
8.70
21.0 (H)
Halo:
35*4-44.0 2.5-2.0
0.15
0.05
1.00
0.05
Long spacing
50.21 Av.:
(
i
s
I
20=2
M-43 54
FIGURE 10
CaStr2 AND HStr
Coswell sample E-39-i. 1 mole CaStro to 1/4
mole HStr. Heated to 210°, slow-cooled to
155°» held there for one hour, quenched in
dry ice-alcohol.
Obs. 29
Corr.
d/n _I
1/59
Half width
degrees 29
5.19
16.80 12 0.20 0.62
7.03 12.45
2
0.03
0.90
8.69 10.09 7
0.12 0.54
10.38
8.47
2 0.03
0.60
12.13
7.26
3 0.05 0.70
15.77
5.60 1 0.02 0.90
20.0 4.42 Present
21.36 4.15 59
1.00 1.38
22.5
3.94 Present
23.79 3.73
6 0.10 O.85
26.0 3.42
3 0.05
2.00
36.0
2.49
2 0.03 0.69
38.3 2.35
2 0.03
1.20
40.9
2.20 2 0.03
1.20
43.1
2.10 2 0.03
2.10
45.3
2.00 1 0.02 0.90
Long spacing
n d
3 50.40
4 49.80
5 50.45
6 50.79
7 50.79
9 • 50.35
Av.: 50.43
2©=50° M-47 55
FIGURE 11
CaStr2 AND HStr
Coswell sample E-39-ii. 1 mole CaStrg to
1/2 mole HStr. Heated to 210°, cooled to
155°> held there one hour, quenched In dry
ice-alcohol.
Corr. Half width
Obs. 20 d/n _1 1/72 degrees
5.19
16.80 14
0.19 0.51
6.90 12.68 2
0.03 0.50
8.64
10.15 7
0.10 0.56
12.08 7.28
3
0.04 O.50
15.66
5.63
2
0.03
0.42
20.0 4.42 Present
21.30 4.16 72 1.00 1.12
23.65 3.75
22
0.31
1.32
26.0 3.42 6 0.08 1.90
35.87
2.50 4 0.06 1.00
Halo:
36.8-48
2.4-1.9
4 0.06
38.0 2.36 2
0.03
0.90
40.6 2.22 2-
0.03
0.84
42.8 2.11 1 0.01
0.53
Long spacing
n
3
4
5
7
9
Av.:
50.40
50.72
50.60
50.98
50.81
50.70
2Q=2
M-42 56
FIGURE 12
CaStr2-HStr
Obs. 20
Corr.
d/n I 1/74
Half width
degrees 2©
4.7 (s)?
18.80
3
0.04
0.5
5.15 16.93
11
0.15
0.48
6.58 13.29
2- 0.03
1.00
8.66 10.14
5 0.07
0.50
12.06 7.30 2
0.03
0.86
15.6 5.66 2 0.03
0.82
16.6 5.32 2 0.03
0.60
17.7 4.99
2 0.03
1.10
20.0 4.42 Present
21.18 4.18 74 1.00
1.19
22.3 3.97
Present
23.38 3.79 23 0.31
1.20
24.55
3.616
3
0.04 0.70
26.2 3.39
2
0.03
2.00
Halo:
33.6-48.0 : 2.7-1.9 3
0.04
0.80
35.8 2.50 2
0.03
38.0 2.36 1 0.01 0.80
40.3 2.23
2 0.03
1.40
42.8 2.11 2 0.03 0.57
Long spacing
n
1
*1 —2
3 39.87 50.79
Av
5
7
9
•
• • 39.9
50.70
51.07
50.94
50.88
M-51 57
FIGURE 13
CaStr^-HStr
1 mole CaStrg* 1 mole HStr, heated to 200° in
calorimeter, held one-half hour, cooled in
calorimeter to room temperature.
Corr. Half width
Obs. 29 d/n _I 1/38 degrees
5.30 16.46 4 0.18 0.70
6.10 14.32
13
0.34 0.56
7.24
12.09
Position uncertain
7.90 11.09
Position uncertain
8.8o
9.97
2
0.05
0.44
9.75 (s)
9.01
3
0.08
0.35
10.21 8.61
7
0.18 0.58
19.70 4.49 29
0.76
1.15
21.31
4.16 22 O.58 1.06
22.57 3.93 38 1.00 1.00
23.70 3.74 14
0.37 1.15
24.5
3.62 Present
26.5 3.36 4 0.11 0.70
28.0 3.18 1
0.03
0.80
29.4
3.03
1
0.03
1.20
31.2 2.86 1
0.03
1.00
32.7 2.73
1
0.03
1.10
34.3
2.61 1 0.03 0.50
35.8 2.50 1
0.03
0.70
38.6
2.33
1
0.03 0.70
40.2 2.24 1
0.03
0.80
43.3 2.13
1
0.03
0.60
Long spacing
n
£l
-2
-3
3
49.38 42.96
5
49.84 43.02 45.04
Av.: 49.61
42.99
45.0
I
I
I
1
I
i
20=2
C-l 58
FIGURE 14
CaStr2-HStr
CaStr2 #5> one mole; HStr (Neo-fat I-65),
two moles. Heated to l60° In calorimeter,
slowly cooled in calorimeter to room temper
ature .
Corr. Half width
Obs. 20 d/n _I 1/52 degrees 20
4.08 21.29
10 0.19
0.32
6.09 14.35
52 1.00 0.46
6.63 13.19
4 0.08 0.27
7.58 11.56 4 0.08 0.50
8.16 10.74 4 0.08 0.46
9.53 (s)
9.21
3
0.06 0.28
10.12 8.68 18
0.35
0.48
12.22 7.20 2 0.04 0.26
13.04
6.95
1 0.02 0.40
14.14 6.23 5
0.10 0.48
16.45 5.37
2 0.04 0.40
17.41 5.07
2 0.04 0.33
19.42
4.55
50 0.96 O.67
20.13
4.40
5
0.10 0.42
21.34 4.15 43 0.83
0.68
22.01 4.03 9 0.17 0.49
23.02 3.85
20 0.38 0.54
23.74 3.74 25
0.48 0.98
24.91
3.56 28 0.54 0.70
26.68
3.33 5
0.10 0.80
27.85
3.20 2 0.04 0.60
29.50 3.02 2 0.04 1.42
31.08 2.87
2 0.04 0.70
32.75 2.73
2 0.04 1.07
34.08 2.63
2 0.04 0.36
35.95 2.49
2 0.04 1.44
38.30 2.35 5
0.10 1.40
40.26 2.24 10 0.19
0.80
42.40 2.13
2 0.04 0.47
43.38 2.08 3
0.06 0.40
45.50 1.99
2 0.04 1.40
47.70 1.90 3
0.06 0.60
Long spacing
n
£l -2
d
Av.: 46.53 43.31
39.6
■ 20=50°
1
RDV x—1 59
FIGURE 15
NEOFAT 1-65 |
Neofat 1-65 from 1 lb. sample box, lot 6643. 1
Corr. Half width
Obs. 20 d/n __I 1/30 degrees
4.42 19.68 4 0.13 0.33
5.93 (s) 14.73 5 0.17
0.80
6.57 13.31
30 1.00 0.44
8.70 10.08 3
0.10 0.46
9.85
8.92 2 0.07
0.32
10.92 8.05
12 0.40 0.65
15.35 5.75
4 0.13 0.55
Long spacing
n
d_
-1 —2
3 39.93 44.19
4 40.32
5 40.25
44.58
7
40.22
Av
*
• * 40.18 44.39
20= 2°
I ” 29=50°
i
i
i
j
i
(
i
o
!_ J29==2_
RDV x-2
FIGURE 16
NEOFAT 1-65
Neofat
1-65
from 30 lb. sack.
Corr. Half width
Obs. 29 d/n 1/36 degrees 29
4.43 19.64
5
0.14 0.40
5.90 (s) 14.80 6
0.17
0.60
6.54
13.27 36 1.00
0.55
10.05 . 8.74 2 0.06 0.70
10.97
8.01 12
0.33 0.57
15.41 5.72 3
0.08 0.58
Long spacing
n
*1 -2
3
39.81 44.40
5 40.07 43.7
7 40.07
Av.: 39.98 1*4.05
29=50
RDV x-3
61
FIGURE
17
STEARIC ACID
Stearic acid 5R3 (MJV);
recrystallized
Neofat from acetonitrile •
Corr.
Half width
Obs. 20 d/n _I 1/96 degrees 29
4.43 19.64 26 0.27 0.33
6.55 13.35
96 1.00 0.42
8.77
10.00
7 0.07 0.35
10.98 8.01
49 0.51 0.49
15.41 5.72 19
0.20 0.46
Long spacing
n
3
4
5
7
Av.:
40.05
40.00
40.04
40.07
40.04
29=50° I C-3 62
FIGURE 18
CaStr2-H20-M0N0PLEX
17-9# CaStr2 #5, 0.6# H20, 81.6# Monoplex.
Heated to 155°> held there one hour,
quenched in dry ice-alcohol.
Corr. Half width
Obs. 2© d/n I 1/20 degrees
5.31 16.43 7 0.35
0.48
7.02
12.47 3 0.15 0.77
8.71 10.07 4
0.20
0.85
19.6 H 4.51 20 1.00
5.3
20.04 4.42 13 0.65 0.63
21.22
4.17 11 0.55 0.67
22.8 (s)
3.89 4
0.20
0.9
26.07 3.41 5 0.25 0.57
40.8 ? 2.21
Long spacing
n d
3 49.29
4 49.88
5 50.35
Av.: 49.84
29=2°
FIGURE 19
CaStr2-n-HEPTAN0L
17.5# CaStr2 #5, 82.5# EK reagent grade
heptanol. Heated to 230°, cooled to 155 >
held there for 15 minutes, quenched in dry
ice-alcohol.
Corr. Half width
Obs. 29 d/n I 1/24 degrees
5.21 16.74
9
0.38
0.57
8.57 10.23 3 0.13 0.79
12.0
7.33
2 0.08 1.0
19.5 H
4.66 24 1.00 5.0
20.19
4.38
7 0.29
1.0
21.35 4.15
10 0.42 O.65
22.5 (s) 3.94
26.0 3.42
3 0.13
0.4
Long spacing
n d
3 50.22
5 51.15
7 51.31
Av.: 50.89
20=50
M-55
64
FIGURE 20
LiStr-CETANE
Coswell sample E-43. Originally 18#
LiStr, 0.6# HpO, remainder cetane.
Heated to 200°, cooled to 155° > held one
hour, quenched in dry ice-alcohol.
Pressed at 10 psi, lost 45# cetane by
weight of original system.
Corr. Half width
Obs. 2© d/n I I/67 degrees 20i
Halo:
1
1
4-12
21.7-7.3 9 0.13 ■ i
6.55 13.35
10 0.15 0.43 !
10.95 8.03 3
0.04 0.60 1
Halo:
|
12-32 7.3-2.8 1
Max.:
1
18.96 4.66
67
1.00 6.78 !
20.93 4.23 33 0.49
0.62 j
22.10 4.01 8 0.12 0.87 i
23.82
3.73
8 0.12 0.70 j
24 .85 3.57
8 0.12 0.88
26.4 (s)
3.37
2 0.03
1.00 1
29.85 2.99
2 0.03
1.06 !
36.08 2.49 3
0.04 0:50 j
Halo:
i
37.4-41.9
2.4-2.1
5 0.07
1
1
37.9 2.37
2 0.03
0.90 :
39.55
2.28 4 0.06 2.0 :
*
Long spacing
n d
3 40.05
5 40.15
Av.: 40.10
C . PRESSURE S T A B IL IT Y
Method of calculation of results from data. Before
presenting the accumulated data and discussing their
validity, it is necessary to elucidate in detail the treat
ment of the data by which .the final results were obtained.
Farrington and Humphreys (11) found that the data
they obtained by use of the Herschel apparatus could be
expressed by an equation of the form
t/s = a + bt
where t is the total time of application of pressure in
minutes and s is the total per cent loss on the basis of
original weight of sample after time, t. The equation is a
linear representation of the asymptotic character of the t
versus a plot. The advantages of this equation lie in the
fact that it is possible to calculate the per cent loss for
an infinite time of pressure application and also the ini- '
tial rate of loss of liquid by the relations
S = i ds _ 1_
b dt a
It is also possible to obtain a value for the loss
at infinite time by extension of the t versus a curve to an ;
asymptotic value, but graphical determination of initial
rate of., loss, _or .rate of loss, at .any..time is .difficultThe
66
initial rate of loss is potentially significant as repre-
• senting the state of the original unpressed system. Its
significance has been discussed by Farrington and Humphreys
(11) and Doscher (7) as it applies to the Herschel method.
Farrington and Humphreys (ll) found it unnecessary
to make any corrections or additions to the ultimate loss
or initial rate so determined. However, in the present
apparatus it was found that the thimble was capable of re
taining liquid since a gain in weight of the thimble was
observed after the solid residue had been removed from the
thimble after the run.
Despite the presence of this complicating factor, the
data of the runs in the present study were also found to
follow the linear relation found by Farrington and
Humphreys.
The calculation of the ultimate (t = oo) loss and
the initial rate of loss can be explained best by means of
an illustration of the method, using actual data as follows.
The calculation of-the total per cent (or total ultimate)
loss is to be carefully noted.
Sample E-22
17*9$ CaStr2
4.1$ HStr Initial Composition
78.1$ Cetane
Total weight of original system as prepared: 5»0
grams
_Pressure applied in both runs_was„10.p.s.l.______
67
Hun I
Wt. thimble and sample: 4.2306
(dry) : 2.5490
1.68l6
t (min.) Wt. of total system Total wt. loss s t/s
5 4.0067 0.2239 13.3 0.376
10 3.8948 0.3358 20.0 0.500
20 3.8050 0.4256 25.3 0.789
30 3.7606 0.4700 28.0 1.07
40 3.7374 0.4932 29.3 1.36
Wt. thimble after run : 2.6303
" " before run: 2.5490
Wt. gain : 0.0813
Run II
Wt. thimble and sample: 4.0909
" " ; 2.6195
1.4714
Wt. thimble after run : 2.6913
" n before run: 2.6195
Wt. gain : 0.0718
t (min.) Wt. of total system Total wt. loss s t/s
5 3.8528 0.2381 16.2 0.309
10 3.7519 0.3390 23.0 0.434
20 3.6788 0.4121 28.0 0.712
30 3.6417 0.4492 30.5 0.983
40 3.6197 0.4712 32.0 1.25
Calculation of results: The data of both runs are
plotted as t/s against t in Figure 21. From the straight
lines the calculated ultimate loss for Run I is 35.2$, and
for Run II, 36.6$. These figures are the reciprocals of
the slopes of the respective straight lines. In addition,
the thimble correction adds 4.8# to the ultimate loss
68
0 Run II
.FIGURE 21
t/s vs. t FOR SAMPLE E-22
1. 0
calculated for Run I and 4.9# to the ultimate loss calcu-
|lated for Run II. The combined result represents the total
i
'ultimate (or total per cent) loss.
!Total ultimate loss = Calculated ultimate loss +
i i
j '
; thimble correction f
Thus, the total ultimate loss for Run I is 40.0$,
and for Run II, it is 41.5#.
The reciprocal of the intercept of the t/s-t line
'with the t axis is the calculated Initial rate of loss.
For Run I, the initial rate of loss calculated is 4.53 per
|cent per minute.
I
All points of the t/s versus t plot fell on a good
straight line. However, such behavior was not always
i
i
observed. Very often the behavior illustrated by Figure
22 was found. The t/s versus t curve is observed to be
non-linear at times less than twenty minutes. This behav
ior was particularly marked in samples whose total ulti
mate loss was low (such as concentrated soap-cetane sys
tems) and in the commercial grease systems, which were made
;from oils of very high viscosity. Systems which lost
appreciable quantities of their liquid in relatively short
periods did not generally show such non-linear behavior in !
t
|their t/s-t curves.
10
FIGURE 22
t/s vs. t FOR SAMPLE D-40
38.3# CaStr'g-1.1# H20-Cetane System
(original composition)
T/S
20
70
4 0
30
20
71
Meaning and validity of results. Generally, the
total ultimate loss.determined by the methods Indicated was
found to be fairly constant for different runs on a given
system. Variations among four samples of a given set were
rarely more than three per cent absolute, which is about
ten per cent relative deyiation for a large number of the
systems.
Variations in the initial rate of loss for a given
set of runs,were much greater. The results of the two runs
of Sample E-22 indicate the,order of deviation commonly
found.
The variation in initial rate of loss encountered may
reflect the dependence of results on uncontrollable (at
least at present) factors in the experimental technique,
such as area of the sample in contact with the.thimble,
manner of packing of the sample in the thimble, and the
amount of adhesion of sample to the thimble walls.
Despite the probable existence of such factors in
the technique, the total ultimate loss appears essentially
unaffected by their existence, or at least those factors
appear to have about the same effect in a given type of
system.
One important consideration concerns itself with
the question as to whether the applied gas pressure actually
72
re p re s e n ts the tru e pressure ten d in g to exp el liq u id from
the system. I t must he r e a liz e d th a t the sample is in con
ta c t w ith a h ig h ly porous hody which is capable o f a c tin g
l ik e a sponge. When the grease system is brought in c o n tac t
w ith the th im b le , the th im b le w i l l beg in to absorb liq u id
from the system even b e fo re e x te rn a l p ressure is a p p lie d .
When the sample is first placed in the thimble, there
may be a film of liquid not held In pores of the grease, but
more or less free at its surface. The pressure tending to
cause flow of that liquid into the porous thimble will be
approximately 2fc/r0, where $ Is the surface tension of the
liquid and rQ the pore radius of the thimble. If all of
the liquid originally present in the grease is held in pores
of the grease, the pressure will be approximately
2 V (l/ro “ I/1*)* where r Is the pore radius of the grease.
Presumably the flo w o f liq u id w i l l co n tin ue u n t il
e ith e r the pores o f th e -thim ble are f u l l o r u n t i l the pore
s iz e o f the grease equals th a t o f the th im b le . The d ilu te
soap systems and the v e ry s o ft systems (such as calcium
s te a r a te -s te a r ic a c id -c e ta n e ) were found to lo s e liq u id
r e a d ily to the th im b le ; and fu rth e rm o re , liq u id appeared In
drops on the o u ts id e o f the th im b le . O ther systems were
found to lo s e liq u id slo w ly to the th im b le on stan d in g , b ut
no fr e e liq u id appeared on the o u tsid e o f the th im b le .
73
However, the liquid loss of the grease systems to
the thimble was extensive only in the case of the very soft
and the dilute systems. The losses observed when external
pressure was applied were in all cases much greater than
those found when the thimble and grease were allowed to
stand undisturbed. It is probable that the primary cause
of liquid loss was the effect of external pressure in forc
ing solid particles closer together.
Possible effects of the thimbles on amount and,rate
of loss from the grease samples were examined. The thimbles
were immersed in cetane for five minutes, removed and
allowed to drain for five minutes, and then wiped with a
clean towel. The cetane-saturated thimbles were then sub
jected to 10 psi pressure for periods of time.
There were variations in both rate of loss and total
ultimate loss of liquid from the cetane-filled thimbles.
Total losses ranged,from 50$ to 80$ on the basis of liquid
originally present in the'thimble. Significantly, no linear
t/s-t relatipn was followed in any case, and an exact deter
mination of rate of loss was not possible. The nature of
the t versus s curves clearly indicated differences in rates
of loss from the different thimbles.
Examination of the data for given systems and com
parison with the liquid retentiveness and rate of loss from
74
the th im b les as determ ined above f a ile d to re v e a l any sys
te m atic dependence o f t o t a l u ltim a te lo s s and i n i t i a l r a te
o f lo s s o f systems in a g iv en s e t on th e above c h a ra c te r is
t ic s o f th e th im b le s .
V a ria tio n s in th e o r ig in a l w eights o f sample in a
g iv en th im b le amounted to about 10$ based on an average
w eigh t o f sample. T h is v a r ia tio n in d ic a te s th a t samples
were pressed in to the th im b les w ith v a ry in g degrees o f
packing , sin ce the d e n s itie s o f th e samples would be expect
ed to show no such v a r ia tio n , nor in the manner in which
the samples were observed to v a ry in w eight as a fu n c tio n o f
V *
soap c o n te n t.
C onsiderable v a r ia tio n in the amount o f liq u id in th e
th im b le a t th e end o f th e run was observed. The t o t a l tim e
o f th e ru n appeared to have no system atic in flu e n c e on th e
q u a n tity . There was a rough r e la t io n between the c a lc u la te d
u ltim a te lo s s ( l / b ) and th e liq u id rem aining in th e th im b le ,
alth ou gh a g a in , the r e la t io n was s u b je c t to co n sid e rab le
v a r ia tio n .
S tu d ie s so f a r have n o t re v e a le d the e x te n t to which
th e d a ta depend upon s p e c ific ex p erim en tal v a ria b le s , p a r ti
c u la r ly since i t has not been p o s s ib le to is o la te and d e fin e
the p o s s ib le v a r ia b le s ,in in s ta n c e s .
C onsequently, it-c a n n o t be assumed a t p re s e n t th a t
75
th e t o t a l u ltim a te lo s s and i n i t i a l r a te o f lo s s a re unique
p ro p e rtie s o f the grease systems. V ery e v id e n tly th ey
depend upon the n a tu re o f the method used f o r t h e ir d e te r
m in a tio n . A t p re s e n t, the r e s u lts are u s e fu l o n ly f o r com
p a ra tiv e purposes, sin ce d iffe re n c e s in b e h av io r do r e f le c t
d iffe re n c e s in systems. The use and va lu e ( a t p re s e n t) o f
the re s u lts o f the pressu re s t a b i l i t y method w i l l become
c le a r e r by d em onstration.
P re c is io n o f the r e s u lt s . C onsiderable d i f f i c u l t y
was encountered in a c h ie v in g c o n s is te n t r e s u lts w ith one
system unless th e p re p a ra tiv e technique was c a r e fu lly con
t r o lle d . T h is exp erience in d ic a te d th a t the number o f v a r
ia b le s which c o n tro lle d th e pressure s t a b i l i t y o f the sys
tems s tu d ie d was la rg e and t h e ir e f f e c t als o g re a t f o r
r e l a t i v e ly s lig h t m o d ific a tio n s in procedure.
• I n i t i a l l y , i t was hoped th a t i t would be p o s s ib le to
p repare sm all sample tubes under c o n d itio n s s im u la tin g to
some e x te n t those used in the commercial p re p a ra tio n o f
g reases. When samples were cooled in a i r , in many cases
th ey were found to be non-homogeneous when opened a t room
tem p e ra tu re, and th e re fo re u n s u ita b le fo r the purpose in
mind. On c o o lin g the samples in a i r , o p a c ity appeared
around the bottom o f the tube f i r s t and spread upward non-
u n ifo rm ly , the o u te r p o rtio n s o f the sample becoming opaque
76
before the inner portions in most cases. The non-uniform
rate of cooling could very well account for the inhomo
geneity of some of the systems.
Standardizing the size of tube and sample and quench
ing the systems from one temperature improved the precision
of the results somewhat, but the precision was still gen
erally unsatisfactory.
It was found that a heating period of one hour at
the elevated temperature was sufficient to give agreement
between successive tubes in addition to the quenching
practice. Samples held at the elevated temperature for
four hours gave the same results as samples held one hour
at the same temperature. Table III shows the difference in
the degree of precision attained between systems heated for
different lengths of time.
It Is clear from Table III that the agreement is
much better among the tubes allowed to heat for one hour or
more. Only two out of a total of eight results of the lat
ter set are poorer than the mean deviation. By discarding
the two poorest results, the average for tubes heated for
one hour becomes 29.6$ and the average deviation becomes
1.2$.
A considerably greater divergence is shown by the
former set. The precision within a pair of samples from
77
TABLE III
PRECISION AS A FUNCTION OF HEATING TIME
Time held
at 155°
$ soap
(wt. basis
$H20
of sys.)
Total %
loss (calc.)
Deviation fron
average
5 min. or
less
17.5 0.53 34.1);
32.4)
0.4;
2.1
17.1
O.51 28.8);
28.3)
5.7;
6.2
17.1 0.51
40.4);
37.1)
5.9;
2.6
18.0 0.52 3°*4);
32.6)
4.1; \
1.9
17.8 0.52
41.3);
39.2)
6.8;
4.7
Av.:
17.5 0.52
34.5
4.0
1 hour
17.3 0.51 26.7);
22.3)
3.1;
7.5
17.8 0.54 31.4);
29.2)
1.6;
0.6
17.8 0.54 29.4);
38.6)
0.4;
8.8
18.0 0.54
31.3);
29.7)
1.5;
0.1
Av.:
17-7 0.53
29.8 3.0
Samples from one tube are bracketed together.
78
the same tube is generally good, but there is lack of close
agreement from tube to tube, indicating that the method of
measurement is satisfactory, and that it is the systems
/
themselves which differ, which is to be expected if the
conditions of formation differ. Despite the evident lack
of agreement among the various samples of this set, the
agreement is nevertheless better than it is for systems in
which the rate of cooling was not as closely controlled,
since runs made on samples from one tube agreed more close
ly when the system had been quenched.
The absolute precision appeared to be largely unaf
fected by the total liquid loss, as examination of Table IV
shows. Nor did the type of system investigated appear to
have- any effect on the precision.
It was with some reluctance that the procedure call
ing for* the quenching of the cetane systems was adopted since
this involved freezing the cetane and then melting it. Such
behavior would reasonably be expected to affect the nature
of the system studied. The behavior of the cetane systems
when suddenly quenched, however, differed in behavior on
melting from systems in which cetane froze slowly. The
quenched systems were of a non-crystalline appearance, being
hard cakes. It is possible that the cetane solidified in a
microcrystalline state.
TABLE IV
PRECISION VS. TOTAL. LIQUID LOSS
CaStr2-H20-CETANE SYSTEMS (10 PSl)
Original $ CaStr2 Total Ultimate Deviation from
(wt. basis of system) Loss (calc.) Average
10.2
Av,
67.7
64.6
66.3
65.8
66.1
1.6
1.5
0.2
0.3
0.9
38.4
Av.
10.5*
8.1
6.9
8.4
7.8
2.7
0.3
0.9
0.6
0.6
♦Discarded.
I In the slowly frozen cetane systems, such as those 1
formed when samples stood overnight at temperatures below |
i
\
the freezing point of pure cetane (18.5°), large crystals j
of cetane were formed, giving the frozen system a silken j
j sheen. On melting, the large crystals of cetane were not J
j
• reincorporated into the soap-oil system, but remained as
\
| free liquid, separate from the remaining solid material.
An 18$ calcium stearate-0.'5$ water-cetane system was
prepared with the intention of aging it for several days.
However, on standing overnight after its preparation, the
cetane froze and destroyed the original system. The system
was opened, the free liquid mixed back into the system with !
:a spatula, and the pressure stability of the system deter- j
!mined. Table V compared the behavior of this system with a
i
i
j system of the composition which was run immediately after
i preparation.
The system losing an average of 39.8$ liquid was the
i
!system in which the cetane solidified slowly. The effect
i
i is most marked in the initial rate loss, l/a, which reflects
'perhaps that the liquid which was worked back into the
!
jsolid system was actually very loosely held, and not com
parable to liquid retained by systems in which the cetane
did hot solidify slowly.
A most striking effect of the freezing of the cetane
TABLE V
EFFECT OF SLOW CRYSTALLIZATION OF CETANE ON PRESSURE
STABILITY OF lQ% CaStr2-0.5# H20-CETANE SYSTEMS
Original % Soap
(wt. basis
of system)
Original $ Water
(wt. basis
of system)
Total Ultimate
Loss (calc.)
1/a
(calc.)
18.0
0.5
38.8 10.0
40.9 9.1
17.8
0.5
30.0 0.56
82
in a pressure system was observed. The residue, a firm, dry-
appearing cake, from a pressure stability determination was
discarded into a waste crock, where it stood for several
days. One morning, after a particularly cold weekend, when
it is doubtful that the temperature of the laboratory rose
above the melting point of the cetane, the residue was
noticed to have assumed a remarkable appearance. Growing
directly out of the surface of the hard cake were a myriad
of very fine fibers about one centimeter in length which
had a silken sheen. They melted on touching, however.
To summarize the preparative conditions and the exact
pressure stability technique which gave the greatest preci
sion:
Preparation of systems:
1. Weight of sample was always 5-0 gra.
2. Sample was sealed in tube 15 mm. i.d., about 10
cm. long.
3. Sample tube heated in oven to 155° and held there
for one hour (except where heating temperature
was studied).
4. Sample was quenched in dry ice-alcohol.
Pressure stability technique:
1. Sample was allowed to warm up to room temperature
(20°) for 15 to 30 minutes.
1 2. Sample was worked with a spatula on watch glass
for three minutes.
3 . C lean, d ry th im b le was f i l l e d w ith sample.
I Sample was subjected to pressure for 40 to 120 i
|
minutes.
; 3. After run, residue was carefully removed and |
thimble weighed. 1
}
j
i Except where specifically noted, the pressure applied
i ■ ;
iwas 10 psi. The 10 psi was found sufficient to cause ex
pression of appreciable portions of the liquid. The effect
'of higher pressures will be discussed in a separate section.
i 1
1
Effect of soap content on pressure stability of J
1
jcalcium stearate-water-cetane systems. A study of the
! effect of soap content on the amount of liquid loss from
the stated systems was undertaken. The results are summa-
l
r iz e d in Table V I and shown in F ig u re 23 . A ll fig u re s !
c ite d except where s p e c if ic a lly noted a re the average o f
fo u r ru n s, two from each o f two tubes o f the same composi-
i
I
Ition.
1
: Effect of water content on pressure stability of l8$>
i CaStrg-water-cetane systems. One of the more obvious var
iables worthy of consideration is the effect of water
84
TABLE VI
EFFECT OF SOAP CONTENT ON PRESSURE STABILITY OF
CaStr2-H20-CETANE SYSTEMS (10 PSI)
Original % Soap Original $ H20 Total Ultimate l/a (calc.)
(wt. basis of system) Loss (calc.)
10.0
0.3
66.1 * 0.9 14.9 ± 3.4
12.8 0.4 53.2 * 2.2 8.2 * 1.2
17.8
0.5
30.0 * 2.6 O.56* 0.12
24.9 0.75
20.1 * 1.6 0.44* 0.08
29.7 0.9 14.3 ± 0.6 0.27± 0.02
38.3
1.1 7.8 * 0.6 0.13* 0.02
45.0
1.35 2.7 ± 0.2 0.02
%LOSS/| 0
FIGURE 23
PER CENT LOSS VS. COMPOSITION
FOR DATA OF TABLE VI
INITIAL. % SOAP
4 5
30
content on pressure stability, other factors being kept
constant. The soap content of the present set of systems
was 18.0# within 0.2#. The results are summarized in
Table VII and shown in Figure 24.
Effect of stearic acid content on pressure stability
of 18# calcium stearate-stearic acid-cetane systems. Since
stearic acid had been found to prevent syneresis when
included in calcium stearate-cetane systems, and since it
is also known to stabilize commercial greases against syn
eresis, a study of the effect of stearic acid was under
taken by varying the acid content. The soap content was
kept constant at 18.0 dt 0.2#, the stearic acid content
increasing at the expense of the cetane. The results are
summarized in Table VIII and Figure 25.
i Effect of methanol on pressure stability of 18#
calcium stearate-methanol-cetane systems. Methanol was
found to exert a stabilizing influence on systems of cal
cium stearate and cetane with respect to preventing syn
eresis. Methanol, like water, is sparingly soluble, if
soluble at all, in cetane, since cetane shaken with
methanol at room temperature retains its refractive index
within experimental error. Stearic acid, however, is
soluble in cetane above a temperature of 50° in dilute
87
TABLE VII
EFFECT OF WATER CONTENT ON PRESSURE STABILITY OF
18# Castr2-H20-CETANE SYSTEMS (10 PSI)
% H20
(wt. basis mol HpO Total Ultimate Loss
of system) mol soap (calc.) l/a (calc.)
0.1 0.19 39.0 ± 0.5 3-3 ± 0.7
0.23 0.43 34.4 ± 0.9
0.75 ± 0.3
0.50
0.95
30.0 + 2.6 0.56 ± 0.12
0.75
1.4 32.4 ± 1.7 1.8 ± 0.6
1.0 2.1 35.2 ± 2.2
2.7 ±. 0.9
% 110S S/,0
4.0
3.0
FIGURE 24
PER CENT LOSS VS. WATER CONTENT
FOR DATA OF TABLE VII
MOL HgO/MOL SOAP
89
TABLE VIII
EFFECT OF STEARIC ACID ON PRESSURE STABILITY OF
18# CaStr2-HStr-CETANE SYSTEMS (10 PSI)
Original % HStr
(wt. basis
of system)
Mol acid
Mol soap
Total Ultimate
Loss (calc.) l/a (calc.)
0.6
0.07 35.4 ± 2.3 5.0 + 1.7
1.0 0.12 31.8 + 0.7 1.6 ± 0.06
2.0 0.236
26.7 ± 1.2
1.2 ± 0.4
3.0 0.354 34.7 ± 0.0 1.3 ± 0.2
4.0
0.473
40.8 + 0.8 6.7 ± 1.2
5.° 0.59 48.5 ± 2.4 7.1 + 1.8
6.0
0.71 5^.7 ± 0.5 16.5 ± 3.5
7.0
0.83 48.9 + 0.7 18.5 ± 3.7
10.0 1.18
41.7 ± 0.9
18.0 ±. 2.0
5 0
% uoss
FIGURE 25
30
PER CENT LOSS VS. HStr CONTENT
FOR DATA OF TABLE VIII
m o l acid/m o l s o a p
.47 .94
91
solution. It was of interest to compare the behavior of
i
methanol with respect to its concentration effect on pres
sure stability. The soap content was 18.0 jb 0.2# in all
the systems. The results are shown by Table IX and Figure
26.
It is evident that the methanol systems behaved in a
manner analogous to the stearic acid systems. The nature
of the least stable system (3*98# MeOH) was exceptional.
The system was very soft, so soft in fact that it could be
poured into the thimble. While thimble and contents were
weighed, liquid appeared on the outside of the thimble, and
the system seemed to be undergoing a filtration without the
benefit of external pressure.
Effect of oil on pressure stability of calcium
stearate-water-cetane systems. In addition to cetane,
other solvents were used for dispersing the soap and water.
The soap content was 18.0 dt 0.2# in all cases. Solvents
used were decalin, Nujol, and Monoplex.
The decalin system was run in duplicate, and although
there was some evaporation of decalin, a satisfactory t/s-t
plot was obtained for all runs. Only one Nujol system,
however, was run, as was the case with Monoplex. The
results of these experiments, along with the figures for
the comparable cetane system, are summarized in Table X.
92
TABLE IX
EFFECT OF METHANOL ON PRESSURE STABILITY OF
18$ CaStr2-MeOH-CETANE SYSTEMS (10 PSI)
Original % MeOH
(wt. basis Mol MeOH Total Ultimate Loss
of system) Mol Soap (calc.) l/a (calc.)
0.47 0.5
39.8 ± 1.2
1.0
1.05 36.9 ± 1.0
1.43
1.5
34.0 + 1.2
1.8
1.9
37.6 ± 0.2
2.0 2.1 41.7 ± 0.2
2.14
2.25
44.1 + 0.6
2.66 2.8
51.3 ± 0.5
3.10
3.25 54.9 ± 0.8
3.98 4.2 66.3 + 0.2
4.2 4.4
63.7 ± 0.4
5.8
2.9
5*3
6.3
5*?
5.4
14.0
33.4
111
44.0
± 0.5
± 0.3
± 0.3
+ 0.0
± 0-3
± 0.6
± 2.9
± l*1
± 5-0
+12.3
60
% LOSS
40
FIGURE 26
PER CENT LOSS VS. MeOH CONTENT
FOR DATA OF TABLE IX
20
% MEOH
94
TABLE X
EFFECT OF OIL ON PRESSURE STABILITY OF
18# CaStr2-0.5^ H20-0IL SYSTEMS (10 PSl)
Oil Orig. % CaStr2
(wt. basis)
Total
Loss
Ultimate
(calc.) l/a (calc.)
Cetane 17.8 30.0
± 2.6 O.56 + 0.12
Decalin 18.0 49.1
+ 2.6
4.3 + 0.7
Nujol
17.9
40.1 + 4.1 0.40 ± 0.19
Monoplex
17.9 37.3
+ 2.4 1.8 ± 0.2
The results of the foregoing table are contrary to
those of Farrington and Humphreys (11), who found that their
ultimate loss for a given soap stock and soap content was
independent of the oil used to prepare the grease, although
the value of l/a reflected the different nature of the oil,
the effect of the viscosity of the oil being evident. It
is possible that the difference in results may be due to
the differences in the two methods.
The l/a value for Nujol does not adequately reflect
the difference in rate encountered for loss from that sys
tem with the rate of loss from the cetane system. Whereas
the cetane systems had lost almost all of their liquid by
the end of 75 minutes, the Nujol system had lost only about
20 per cent of a calculated total of 40 per cent at the end
of 160 minutes. About 75 minutes were required for the
t/s-t plot to become a straight line. This behavior com
pares with that encountered in the commercial greases and
is to be attributed to the high viscosity of the Nujol.
A comparison of l/a values may not be justified in
the present instance because of the divergence of the Nujol-
containing system from the behavior predicted by the empir- ■
ical equation.
Effect of pressure on the liquid loss of calcium
stearate-cetane systems. One of the most important
96
variables to study, both from the standpoint of obtaining !
1
information concerning the nature of the systems studied
r«
and from the standpoint of determining the region of appli
cability of the apparatus, was the effect of pressure on the
amount of liquid which could be expressed from various .
systems.
~ i
Calcium stearate-cetane-water systems of two differ-j
ent compositions and calcium stearate-stearic acid-cetane '
and calcium stearate-methanol-cetane systems were chosen. ;
t
The stearic acid and methanol systems selected were those
i
which gave the smallest liquid loss of their respective
series at 10 psi. The results are summarized in Table XI. ■
The 15*0$ calcium stearate-cetane-water system was
prepared differently from the other systems. 15.0 grams of
the system were prepared in one tube. Furthermore, the tube
I
was heated one hour at 170° instead of 155°> which is cus-
I
tomary. Only one determination at each pressure was pos- i
sible because the total amount of sample had to bp spread ;
over a number of runs, !
The other systems were prepared in the customary ■
manner. The results of the loss as a function of pressure ;
for the 10 per cent system are interesting. It might be
concluded that pressure has little effect on the quantity
of liquid capable of being expressed from that system,
97
TABLE XI
EFFECT OF PRESSURE ON PRESSURE STABILITY OF
CALCIUM STEARATE-ADDITIVE-CETANE SYSTEMS
f o Soap % Additive Pressure Total Ultimate l / a
(wt. basis of system)
(p s i)
Loss (calcd.) (calcd.)
15.
,0
0.5 h2o
10 30.4 1.1
20 29.0 0.96
30 32.3
5.0
40
34.5
4.1
50 30.2 2.6
10.,0
0.3
h20 10
20
66.1
65.4
+
+
0.9
1.9
14.9
17.5
i.
3.0
2.0
30 69.1 ±
0.8
22.3 ± 0.5
40 60.0
±
1.0 32.6
± 3.1
18. ,0
0.5
h2o 10 30.0
±
2.6 0.56
±
0.12
25
37.2
±
1.4
2.9 dh
1.0
4o
37.3 ±
0.6
3.9 ± 0.3
18.0 2.0
HStr
10
26.7
± 1.2 1.2
±
0.4
25 36.5 ± 0.5
1.6
±
0.1
18.0
1.5
MeOH 10 34.0
±
1.2
5-3 ± 0.3
25
42.4 + . 3.4 5.2
± 1.9
which loses a majority of its original liquid at the low
pressure (10 psi). The values of l/a, however, reveal a
dependence on the pressure which.is reasonable, a greater
external force causing a more rapid initial collapse of
the solid structure.
The results with the 15 per cent calcium stearate
system are puzzling. Again the total loss shows little
dependence on the applied pressure, and the results are
apparently erratic, since the loss at 10 psi and 20 psi
are essentially the same, but jumps when the pressure is
Increased to 30 psi. The loss at 50 psi apparently re
verses the somewhat upward trend of the loss as pressure is
increased, and the loss is approximately that for a pressure
of 10 psi. The values of l/a show the same sort of appar
ently erratic behavior. The entire set of data are to be
regarded with considerable suspicion, lacking a suitable
explanation of the results in terms of the structure of
the solid.
Comparison of the losses from the water, stearic
acid, and mechanol additive systems at 10 psi and 25 psi
indicates that the pressure stabilities of the three sys
tems lie in the same order at both pressures. However, the
per cent increase in loss at 25 psi in the stearic acid sys
tem is 36.7 based on the loss at 10 psi, whereas the per
I 99
cent increase in loss at 25 psi in the water and methanol
additive systems is 25.0 based on the loss at 10 psi. Such
behavior indicates that the pressure dependence of ultimate
loss is greater in the stearic acid system than either the
water or methanol systems. It is evident, however, that
I
the apparent dependence of l/a on pressure is the greatest
in the water system, the values of l/a for the other two
systems showing little variation on increasing the pressure;
Any interpretation of the results above in terms of
effects on the solid structure would have to be founded on
the assumption that the effects observed originate solely
within the solid structure and not from any external experi
mental conditions, which is an unwarranted assumption at I
present.
Effect of aging on the pressure stability of calcium
stearate-water-cetane systems. Samples of 18$ calcium
stearate-O.5$ water-cetane systems were prepared in the
standard manner and allowed to stand in an air oven at 25°
for varying periods of time, and the pressure stability
determined. The results are shown in Table XII.
It appears that the ultimate loss remains relatively
unaffected by the length of time the above systems stand,
at least up to two weeks. The Initial loss rate appears to
show a small, but apparently real increase as the aging
100
TABLE XII
EFFECT OF AGING ON PRESSURE STABILITY OF
18$ CaStr2-0.5^ H20-CETANE SYSTEMS (10 PSI)
Time of aging at
25° (days)
Total Ultimate Loss
(calcd.) l/a (calcd.)
0 (run immediately)
1
1%
30.0 + 2.6
29.6 ± 0.9
30.2 ± 0.3
29.8 ± 0.6
0.56
1.66
2.0
2.3
+ 0.12
± 0.26
+ 0.0
± 0.56
101 i
process continues. Farrington and Humphreys (11) attempted
to relate the quantity, l/a, to the amount of syneretic
liquid found on storage of their samples for a six-month
period. Examination of their data shows that the two
quantities, l/a and syneretic loss, appeared to be related,
but that the correlation was not outstanding.
Figure 27 is a plot of some of their data, which
is summarized in Table XIII. Two points, corresponding to <
!
bleeding losses of "trace" and "none" are not plotted in
the figure*
< The correlation indicated between l/a and long-term
t
!stability against syneresis coupled with the increase of
(l/a in the present system may be interpreted to mean that
jthe present systems become more susceptible to syneresis on
aging, and that perhaps on sufficient standing, syneretic
liquid might be observed. It therefore seems reasonable to
suggest that It Is perhaps the variation of l/a with time
which can be used as a measure of the syneretic tendencies
i
of the systems. !
Effect of temperature of quenching on the pressure j
*
stability of calcium stearate-water-cetane systems. Samples
i
'of 18# calcium stearate-0.5# water-cetane systems were pre-
i
jpared by heating tubes of the standard size at various tem
peratures for one hour, followed by quenching the samples in
102
% S YNERESIS
IN 6 MONTHS
FIGURE 27
l/a VS. SIX MONTH SYNERESIS LOSS
FROM DATA OF FARRINGTON
AND HUMPHREYS
2
3
4 6
103
TABLE XIII
COMPARISON OF RESULTS OF ACCELERATED SYNERESIS TESTS WITH !
SIX MONTH SYNERESIS FROM DATA OF FARRINGTON AND HUMPHREYS
Syneresis
in 176
days
Oil loss
calcd. for
0.01 hr. b a Soap %
Viscosity
of oil
(ssu)
16.4 20.2 0.0194 0.0003 Na 12.0 180
12.0
11.3
0.0186
0.0007
Ca
7.9
110
6.4
4.5
0.0238 0.0020 A1 12.0
275
5-2
2.7 0.0193 0.0035
Ca
14.5
300
1.7 1.9
0.0225 0.0050 Ca 15.8 110
Trace
3.1
0.0390 0.0028 A1 20.0
275
None 2.0 0.0282 0.0047 Na
24.5
180
104
a dry ice-alcohol mixture and determining the pressure
stability immediately after warming to room temperature.
Results of the total loss and initial rate of loss are
shown in Table XIV.
Except for the result for the 155° system, it would
appear that the quenching temperature has virtually no
effect on the pressure stability of the system studied.
The initial rate of loss, l/a, appears also to be fairly
constant except for the 155° system. Two tubes of the 120°,
175°> ^ d 190° systems were prepared and run. The 155°
result is the average of at least four tubes, two runs from
each tube. Furthermore, the effect of aging on the pressure
stability of systems quenched from 155° would tend to indi
cate that the 30.0$ figure is no artifact.
Despite the difference in initial loss rates and
pressure stabilities, the four systems were qualitatively
similar as regards appearance and feel. All were white,
opaque, non-syneretic masses which were firm and greasy to
the touch.
Appearance of pressed cakes of calcium stearate-
cetane systems. Of some importance is the nature of the
pressed cakes after liquid has been forced out of them.
Pressed cakes resulting from 10 psi appeared to be
uniform in cross section on passing from top of cake to
105;
i
i
l
i j
i
1 TABLE XIV
! !
I EFFECT OF TEMPERATURE OF QUENCHING ON PRESSURE STABILITY !
I OF 1 CaStr2-0. 5^ HgO-CETANE SYSTEMS (10 PSI)
* .. _ - . . _ . . . . . . . -------- .. - . . . . . . t
Temperature from which
samples quenched
Total ultimate
loss (calcd.)
l/a
(calcd.)
120 39.8 i 1.0 2.8 + 0.2
155
30.0 ± 2.6 0.56± 0.12
175
39.4 + 0.6 2.1 ± 0.2
190
40.3 ± 0.3 4.1 + 0.5
J
■ I
\
i
t
i
i __
i
j
1 0 6
bottom, although the bottom, which was in contact with
the thimble, occasionally appeared very 1 1 dry.” The dry
appearance at the bottom of the cake was especially notice
able in the case of systems pressed at higher pressures.
Sometimes a small layer at the top of the cake appeared to
be virtually unchanged from the original unpressed system,
whereas the bottom of the cake was extremely dry appearing.
It might be concluded that liquid was lost from the bottom
of the cake to a greater extent than it was lost from the
top.
One possible explanation of such observations,
although by no means the only one, might be advanced by
assuming that a wall of solid particles is built up against
the thimble as liquid loss proceeds, and that liquid which
might otherwise be expressed is unable to be forced through
the particles which have been forced against the thimble to
form a more or less impervious wall of solid.
As a result, - a decreased ultimate loss on increasing
the pressure seems reasonable if it is assumed that a wall
of impervious solid is built up rapidly at high pressures
and liquid at the top of the cake has virtually no oppor
tunity to be expressed before the wall becomes impervious
to the passage of liquid from the interior of the cake. At
lower pressures the seriousness of such behavior at the
107
| thimble-sample interface is lessened and the loss may .
reflect more nearly the true pressure stability behavior of'
the sample.
i In a l l cases, the o r ig in a l cake was deformed as
liq u id was expressed. The deform ation took p la c e d i f f e r
e n tly , however, depending upon the n atu re o f the o r ig in a l
system, and a p p a re n tly , to some e x te n t, on th e th im b le .
C ro s s -s e c tio n sketches o f ty p ic a l shapes o f re s id u e s are
p ic tu re in F ig u re 28.
(a) was generally observed with systems which were
very soft initially, such as 10 per cent calcium stearate-
0.3 pet* cent water-cetane and the very soft calcium stea-
rate-stearic acid-cetane systems. The residue was not
brittle, but adhered tenaciously to the walls of the thimble.
(b) and (c) were observed with firmer systems. Both,
types occurred with systems of the same composition. The
1 particular shape observed appeared to depend upon the
,thimble, since samples in particular thimbles gave one or
:the other shape. The cakes of type (b) could be removed
easily in one piece and proved to be quite brittle. Type
(c) cakes adhered to the thimble and it was necessary to
scrape them out with a spatula.
An attempt was made to demonstrate that the pressed
cake was in approximately the same condition as an unpressed
FIGURE 28
APPEARANCES OF PRESSED CAKES
109
cake of the same composition, that is, that the pores of
the pressed cake were as completely filled with liquid as
those of an unpressed sample. Such a finding would suggest
that the particles had collapsed completely as liquid was
expressed, not having a sufficiently rigid enough structure
to resist deformation in the absence of liquid.
A measurement of the density of' calcium stearate-
water-cetane systems was undertaken by an approximate
method. A weighing bottle was fitted, with a tight fitting
rubber stopper down to a mark scratched into the ground
glass portion of the bottle. This served to make an approx
imately constant volume pycnometer.
The pycnometer was calibrated with boiled-out, de
ionized water. Successive determinations agreed to within
0.5$. For the density determinations, the residue or
sample was placed in the bottle and the remaining volume
made up with water. Appropriate weighings allowed a cal
culation of the density of the sample. Table XV shows the
results of two density determinations, one on a pressed
sample, the other on an unpressed sample.
The density of the two samples is seen to be virtual
ly the same, despite the differences in treatment. It is
possible to interpret the results as indicating that the
physical state of the pressed and unpressed samples were the
1 1 0
! i
!
: i
i 1
I
I TABLE XV
DENSITY OP PRESSED AND UNPRESSED CAKES
!
Original ' f o soap Original f o HgO
(wt. basis of system)
Pinal $ soap
!
Density J
of cake !
10.0 0.3 30.0
I
0.876 j
29.8 0.9 29.8 O.878
j
i
I
I
I
J
Ill,
same, although such a conclusion does not automatically
follow.
The method of density determination, itself, was j
subject to a certain error, since it is possible that small;
air bubbles could be present in the bottle or in the cake
I
itself. Such an error would make the density of the cake
smaller than its correct value.
Assuming the density of liquid cetane (0.77^ at 20° |
(6)), calculation of the density of the soap (whether as
monohydrate or anhydrous) gives a value of 1.25 gm./cm.3 t
for the density. This value seems rather high, since the !
density of sodium stearate is about 1 gm./cm. , and the sub
stitution of calcium for sodium would not be expected to
increase the density by such an amount. Of course, if the ■
]
packing of the soap molecules is closer in the calcium I
soaps, such a result is not unreasonable. This result is
very interesting, since the most probable error in the
density method is the inclusion of air into the system, ,
which would cause the density of the soap to be too low if
anything.
Of further interest>are the results of experiments
in which pressed cakes were removed from the thimbles,
i
reworked, placed into fresh, dry thimbles, and again sub- ;
mitted to pressure. 10$ and 18$ calcium stearate-water- ;
1 1 2
cetane systems were given such treatment.
The calculated total per cent loss (basis of ori
ginal weight of system) for the 10.0$ (original) soap sys
tem was 67-9$* On this basis, the final per cent soap in
the pressed cake is calculated to be 31-2$, assuming all
loss was cetane. After two successive runs on the same
sample, the actual final per cent soap was 29.9$, and the
final calculated per cent soap was 34.0$.
The calculated total per cent loss for the original
ly 17.6$ soap system was 35-6$. On this basis, the final
per cent soap in the pressed cake was calculated to be
27.4$. The actual final per cent soap in the pressed cakes
after two successive runs was found to be 29.3$, and the
calculated final per cent soap after these two runs was
30.4$ soap.
It would thus appear that one run is not entirely
sufficient to cause expression at a given pressure. How
ever, the difference appears to be small when values of thei
calculated final per cent soap after one run and after two
runs are compared.
Of considerable significance is the observation that
the final per cent soap in the pressed samples is still very
low. Tables XVI, XVII, XVIII, XIX, XX, and XXI give the
values of the final per cent soap for previous systems.
113
i
TABLE XVI
FINAL PER CENT SOAP CALCULATED FOR
CaStr2-H20-CETANE SYSTEMS (10 PSI)
Initial % Soap Final % Soap
(calcd.)
(wt. basis of system)
10.0 29.6
12.8
27.3
17.8 25.4
24.9 31.2
29.7
34.2
38.3
41.6
45.0 46.2
TABLE X V I I
PINAL PER CENT SOAP CALCULATED FOR
18# CaStr2-H20-CETANE SYSTEMS (10 PSl)
Initial # Water mol HpO Final # Soap
(basis of system) mol soap (calcd.)
0.1 0.19 29-6
0.23 0.43 27.4
0.50 0.95 25.8
0.75 1-4 26.6
1.0 2.0 27.7
115
TABLE XVIII
FINAL PER CENT SOAP CALCULATED FOR
18$ CaStr2-HStr-CETANE SYSTEMS (10 PSl)
Original % HStr mol acid Final % Soap
(wt. basis of sys.) mol soap (calcd.)
0.6
0.07
27.8
1.0 0.12 26.4
2.0 0.236 24.6
3.0 0.354 27.4
4.0
0.473
30.4
5.0
0.59
35.0
6.0
0.71
39.8
7.0 O.83 35.3
10.0 1.18
30.9
116
TABLE XIX
PINAL PER CENT SOAP CALCULATED FOR
18$ CaStr2-METHANOL-CETANE SYSTEMS (10 PSI)
Original % MeOH Mol MeOH Final f o Soap
(basis of system) Mol soap (calcd.)
0.47 0.5
30-9
1.0
1.05
28.6
1.43 1.5 27.3
1.8
1.9
28.8
2.0 2.1 30.8
2.14
2.25
32.2
2.66 2.8 37.0
3.10
3.25
40.0
3.98 4.2
53-3
4.2 4.4
49.7
TABLE XX
FINAL PER GENT SOAP CALCULATED FOR
18$ CaStr2-0.5$ WATER-OIL SYSTEMS (10 PSI)
Oil Final % Soap (calcd.)
Cetane 25-5
Decalin 35.4
Nujol 30.0
Monoplex 28.8
118’
i
TABLE XXI
FINAL PER CENT SOAP CALCULATED FOR
CaStr2-ADDITIVE-CETANE SYSTEMS
Original %
Soap
(wt. basis
Original %
Additive
of system)
Pressure
Final % Soap
(calcd.)
15-0
0.5 h2o 10 21.6
20 21.8
30 22.2
40
22.9
50
22.5
10.0 0.3 h2o 10 29.6
20 29.0
30
32.3
40 25.0
18.0 0.5 H20 10 25.4
25
28.6
40
28.7
18.0 2.0 HStr 10 24.6
25 28.3
18.0
1.5 MeOH
10 27.2
25 31.3
----------------------------------------------------------------
i
j
i
j
119
One striking observation to be made from the preced-
ing tables is the relatively small spread of final per cent
soap values, except in the case of the very soft stearic
acid and methanol additive systems. The values seem to all
> be in the neighborhood of 30$ soap in the pressed cake for
18$ systems.
It is also of interest to note from Table XVI that
the limiting compositions of the pressed cakes are not the
same for all systems. For example, the system originally
10$ in soap approaches 30$ soap as a final composition, but
a system Initially 30$ soap can lose liquid Itself and
approaches 3^$ final soap content. The final composition
of systems originally less than 30$ soap nowhere nearly
approach the composition at which no loss whatever occurs,
50$ soap.
It was not found possible to displace the original
liquid from any of the systems. Cetane-containing greases
became mushy when allowed to stand in contact with liquid
cetane, and after standing sufficient periods (two weeks to
one month), the grease underwent physical decomposition.
A calcium stearate-water-decalin system was allowed
to stand in air for some time. The system, originally a
non-syneretic 18$ soap system, was observed to decrease in
volume, become dry-appearing, crack Into numerous small
|pieces, and finally become reduced to a hard, brittle mass
from which no odor of decalin was perceived. ,
An 18$ calcium stearate-82# di-(n-butyl)amine sys- j
tern was prepared. A sample of the system was pressed into .
the metal cap of a sample vial and allowed to evaporate in
,an air oven at 25°. The course of the evaporation was
followed, with the results shown in Figure 29. The result
ant system was a small, hard, crumbly cake which was some
what tan on the surface. It is evident that, despite the
firm, non-syneretic nature of the original system, vir-
i
tually all of the liquid was lost by evaporation.
Pressure stability of lithium stearate-cetane
systems. It has recently been found (28) that lithium
stearate exhibits a relatively simple phase behavior In
cetane, especially in the dilute soap systems. Lithium
'stearate has also been found to give a sharp, reproducible
!X-ray diffraction pattern in the crystalline state. A study
of the pressure stability of lithium stearate systems would
seem to afford a good test of the feasibility of a mechan
ical picture of gel structure in grease systems. The
results with lithium stearate systems studied are summarized
in Table XXII. The history of each sample is given in Table
XXIII. Each of the results in Table XXII comes from only
one tube (two runs).
121
8 0
40
% LOSS
FIGURE 29
EVAPORATION OF LIQUID FROM CaStr,
DI-(n-BUTYL)AMINE SYSTEM
4 0 8 0
TABLE XXII
PRESSURE STABILITY OP LITHIUM STEARATE-CETANE SYSTEMS
Tube No. $ LiStr Solvent $ Additive
(basis of
system)
Total Ultimate
Loss (calc.)
l/a
(calc.)
1 18.0 cetane none
16.9 ± 0.1 0.22 + .03
2 18.0 cetane none
39.5 ± 0.2 3*1 i. .2
3
18.0 cetane 0.6$ H20 45.0 ± 0.4
6.3 ± .4
4 18.0 decalin none 48.0 ± 4.4 1.24 ± .01
123
TABLE XXIII
THERMAL TREATMENT OP LITHIUM STEARATE-CETANE SYSTEMS
Tube No. Treatment
1 Heated to 210°, cooled to 155°, held there
one hour, quenched in dry ice-alcohol.
for
2. Heated to 200° in differential calorimeter (25),
removed, inverted repeatedly, replaced, held at
200° for 15 minutes, slow cooled at normal rate
of calorimeter to room temperature.
3
Same as (l).
4 Same as (2).
; In all eases, a firm, rather elastic grease was
. obtained on cooling. No fiber-like behavior was noted. A
decalin odor was evident when that solvent was used. In
! fact, the decalin in one lithium stearate-decalin system
i
: evaporated so quickly that it was not possible to determine i
its pressure stability.
i
Pressure stability of Commercial greases and resultsj
i the filter paper test. For comparative purposes, five
i
! selected commercial greases were subject to the pressure
i i
stability method, and the results compared with the beha- I
vior found with the well known filter paper test. !
It was found convenient to modify the pressure sta-
’ bility technique in the case of the commercial systems.
I
The greases were weighed into the thimbles, and the system
j
: was allowed to stand in a covered watch glass for two days
■ before subjecting to pressure. In that period, the viscous .
: oil could wet the pores of the thimble. No change in tbtal
loss was caused by that procedure; the Al-2 sample, for ;
example, lost 52.4$ liquid (calculated) when subject to |
i
pressure immediately after filling the thimble, and 54.1$
!when the thimble was allowed to stand for two days.
The difference arose in the t/s-t behavior of the :
I
■ systems. When the thimble was subjected to pressure imme- j
; diately after filling, about 500 minutes were required for j
125
the t/s-t plot to become reasonably linear. The excessive
time required for the attainment of a linear t/s-t plot was
decreased by allowing the samples to stand in the thimbles,
although it was by no means eliminated. The results of the
pressure stability runs are given in Table XXIV.
A run on the Unoba grease was also attempted. The
grease was extremely fibrous, and the thimble was filled
only with difficulty. Several days were required for the
,run, as was the case with the other commercial systems; and ;
it was found that the t versus s curve was not smooth, Jumps
occurring after allowing the partially pressed sample to
stand overnight without application of pressure. Although
it was also necessary to allow the other commercial systems
to stand overnight in the same manner (covered watch glass
at 25°), no such behavior was observed with the other sys
tems. The run was never completed, but at the end of 775
minutes, 32.8$ plus the amount in the thimble (generally
8-10$) had been lost.
Before subjecting the various systems to pressure
stability measurements, the gross samples as they appeared
in the cans (generally about one pound) were observed. The
various samples had stood different, but approximately com
parable, periods of time since receipt in their respective
containers when they were observed. A period of about four
TABUS XXIV
PRESSURE STABILITY OP COMMERCIAL GREASE SYSTEMS
Grease I n i t i a l % Liquid T o ta l U ltim ate l / a Obs. P in a l
(w t. o f system) Loss (c a lc .) (c a lc .) f o Loss
Al-2 88 53.2 .168 41.4 at 870 min.
Ca-1 82
51.5 .107 42.6 at
859
min.
Na-1 84 42.6 .078
34.3
at
1023 min.
Shell Li Ca. 94 (?)
79.9 .151 44.9
at
373
min.
Battenfeld Ca. 90 (?)
45.9 .155
22.4 at 136 min.
127:
months had elapsed between the tim e o f r e c e ip t o f samples
jand t h e ir in s p e c tio n p r io r to s u b je c tin g to p re s s u re . None
o f the samples had appeared to have undergone s y n e re s is ,
I
!although the C a lifo r n ia Research C o rp o ratio n greases
appeared " s lic k ’* on to p , p a r t ic u la r ly the A l-2 g rea se . I t 1
was p o s s ib le to c o lle c t a sm all drop o f liq u id in an in d en
ta tio n in the su rfa ce o f the A l-2 g rea s e . I
, 1
The r e s u lts o f the f i l t e r paper te s t are presented !
:most c o n v e n ie n tly in g ra p h ic a l form , as in F ig u re 30. The
abscissa is log t , t being the tim e elapsed from the s t a r t (
(Of the experim ent in hours. The o rd in a te is log £±A; £±A
is the d iffe re n c e in a re a in mm.^ between the t o t a l area o f
1
the tra n s lu c e n t spot a t tim e , t , and the area o f the blob {
o f grease in the brass r in g , which is assumed to wet the j
I f i l t e r paper a t zero tim e .
j I t is seen th a t the re s u lts o f the f i l t e r paper te s t
appear to fo llo w a r e la t io n o f the form
jc a p illa r y r is e in f i l t e r paper o r in h o r iz o n ta l c a p illa r y
A « k t 0 *66
I t is a m a tte r o f in t e r e s t to note th a t the r a te o f
itubes is g iven by a r e la tio n o f the form
log A = 0 .5 log t + C
o r A = k t 0 , 5
128
LOG
FIGURE 30
RESULTS OF FILTER PAPER TEST
WITH COMMERCIAL GREASES
G AL-2
£ SHELL LI
Q UN0BA-A2
S 7 CA_*
© NA-I 2.0
4,0
3.0
129
if the number of capillaries and the diameter remain the
same in a strip of constant cross section (2). A fuller
discussion is reserved for a later chapter.
Pressure stability of a linde coated silica-cetane
gel. A 17$ "Linde Coated Silica 30"-cetane gel was prepared
by mixing the components in a mortar with a spatula until a
homogeneous mixture was obtained. The mixture was smooth
and translucent. A few drops of free liquid were observed
when the system was allowed to stand several days. The
pressure stability of the sample Immediately after mixing
was determined, and it was found that the total ultimate
loss (calculated) was 32.8$, and the initial rate of loss
was 14$ per minute, which is much greater than that for the
soap-oil systems of similar solid content, although the
ultimate loss was very nearly the same as that found with
the calcium stearate-water-cetane systems. The resultant
cake was brittle, firm, and translucent, although not as
much as the original system. No free liquid was observed
with the pressed cake, even after standing for one week.
On the other hand, a mixture of 75$ Fisher 240 mesh
silica by weight with water was unable to form a coherent
gel-like mass. Instead, the silica settled out rapidly.
A system of 18$ Bentone 18 by weight in cetane was
also found incapable of forming a coherent gel-like system.
130
Addition of small quantities of water and alcohol (2 drops
per gram of system) to two systems did not appear to help
any. Even when the Bentone content was increased to 50$
by weight no coherent mass resulted.
D. SYNERESIS OF ANHYDROUS CALCIUM STEARATE-CETANE SYSTEMS
The pressure stability technique was inapplicable to
the highly syneretic anhydrous systems of calcium stearate-
cetane. However, some idea as to the amount of liquid which
could be withdrawn from such systems was desired. The tech-^
nique described on page 20 seemed satisfactory, even if
somewhat Inexact. The data are summarized in Table XXV.
The figures in the next to last column include the
syneretic liquid plus the liquid extracted by the filter
paper.
The somewhat erratic nature of the results indicates
the crude nature of the experiments. However, the experi
ments served their purpose by indicating the amount of
liquid which could be extracted from such systems.
After extraction of the liquid, the systems were
generally opaque, whitish, felt gummy and grainy both. They
could generally be rolled up into a gummy ball of material.
131
TABLE XXV
LIQUID LOSS FROM ANHYDROUS CaStr2-CETANE SYSTEMS
Original
% CaStr2
Original
% Liquid
% Syneretic
Liquid after
1 week
Total $
Loss
Final $
Soap
5-1 94.9
33.0 89.0
46.3
10.5
89.5 38.5
73-2 39.2
14.5
85.1 33.7
6 2.0 39.2
19.1 80.9 24.5 63.3
52.0
24.0 76.0 19.2
57.7 56.7
25.2 74.8 28.0
59.1 61.5
30.1
69.9
17.2 53-8 65.2
35.0 65.O 12.0 47.0 66.0
39.0 61.0
12.7
40.1 65.2
44.6 55.4 8.2
29.5
63.2
E. REFRACTIVE INDEX OF GEL LIQUID
Expressed liquid from pressure stability experiments
was identified refractometrically. Representative samples
were ehosen for the determination. The results are col
lected in Table XXVI, with refractive indices of pure sol
vents included for comparison. The value for both solvents
was determined directly. The value for cetane was found to
check closely the value found by Deansley and Carleton (6).
It Is to be concluded from the data of Table XXVI
that the expressed liquid in every case was the pure liquid,
or at most, a very dilute solution of soap in oil.
133
TABLE XXVI
REFRACTIVE INDICES OF EXPRESSED GEL LIQUID
Original System Refractive Index (20°)
pure cetane 1.4345 ± 0.0002
decalin (EK practical) 1.4722 ± "
39.0$ CaStr2~6l.0$ cetane (syneretic)
1.4347 "
18.0$ CaStr2-0.5$ HgO-cetane 1.4348 db "
18.0$ CaStr2-0.5$ H20-decalin 1.4723 ± "
18.0$ CaStr2“5.0$ HStr-cetane 1.4348 ± "
18.0$ CaStr2~2.0$ HStr-cetane 1.4348 ± "
18.0$ CaStr2-4.0$ MeOH-cetane 1.4348 ±. "
CHAPTER V
DISCUSSION OP THE VISUAL OBSERVATIONS
Examination of the data of the section on visual
observations in Chapter IV reveals a number of interesting
and potentially important phenomena, both theoretically and
practically.
A striking observation is that the temperature at
which the greatest visual change is observed in dilute
anhydrous calcium stearate-cetane systems is relatively
constant and corresponds quite closely to the transition in
the anhydrous soap with which the largest heat effect is
associated. This 115° transition in the #5 soap is prob
ably the same as the 123° transition occurring in a purer
preparation, being likened to a curd-waxy transition such
as that which occurs in sodium stearate at 117°.
X-ray evidence is presented and interpreted (30) to
indicate that the 115° transition in the more dilute anhy
drous soap-oil systems corresponds to a change from crystal
line soap-free liquid to some liquid crystalline phase
involving both soap and oil, or possible combination of
liquid crystalline solvent-free soap, liquid crystalline
soap-oil> and free liquid. Calorimetric data (27) fail to
reveal any transition of the phase or phases produced at
: 135
! 115°, either to other liquid crystalline phases or to iso-
i
<
: tropic liquid. These observations are in accord with visual
»
I evidence which shows the marked change from slurry to stiff,:
' i
translucent, apparently homogeneous mass which remains, the r
, viscosity decreasing only slightly with increasing tempera
ture up to at least 320° in a sealed tube. j
The X-ray data Indicate that the postulated liquid i
I
crystal phase or phases in the dilute system supercool on
' quenching, but that the reversion to crystalline soap is
! marked on slowly cooling. In either case the resultant |
» i
. system is unsuitable as a grease, as borne out in the syn-
| eresis experiments. The slowly cooled systems yielded soft,;
j white powdery suspensions, or white opaque mushes, even in .
relatively concentrated systems (20$ soap).
Although the X-ray results with anhydrous systems !
i
| have been interpreted to signify a supercooling of a postu-
’ lated liquid crystal phase (30), a major portion of the '
;cetane is obtained on syneresis and by absorption with '
filter paper. Evidently, then, if such a phase, containing !
»
both soap and oil, exists at the higher temperature, on
quenching the phase must undergo partial reversion, the ;
liquid freeing itself from the structure without the assump-
,tion of the crystal form by the soap, or else (more likely) :
the phase contains a very small amount of cetane, the re-
' i
Lmainder.being_present_as_such-in_the-sy.stem.— A-further— -
136
possibility is that the liquid is relatively easy to extract
from the phase.
The existence of two phases in the soap-oil systems
may not be detected visually if the difference in refrac-
1 tive indices is very small, one phase is dispersed very
finely in the other, or if the interfaces are diffuse, or
perhaps all three.
That liquid cetane was present in dilute systems was
strongly suggested by an experiment in which a 20% calcium
stearate-cetane system was heated in an open test tube to
which a long condenser tube was attached. A long pyrex rod
was used as a stirrer.
The tube and contents were carefully heated over a
Fisher burner. From time to time the flame was removed and
the thermometer inserted for readings. The material stif
fened about 120° and cleared to a tannish translucent mater
ial. The system could be easily stirred by the rod. On
raising the temperature, small spherical bubbles appeared
which assumed an ellipsoidal shape on stirring. At about
250°, the bubbles began to increase in number and size, and
by the time 263° had been reached, it was impossible to
carry heating any farther because the mass was foaming so
badly that the entire tube was filled with material carried
upward by large bubbles. This behavior is taken as
137
indication that the solvent, cetane, had begun to boil or
was approaching its boiling point, 286.5 (6) at one atmos
phere. Therefore, it was concluded not only that liquid
cetane is present in the dilute systems, but in addition,
that some semi-rigid structure is present in the system
because of the behavior of the bubbles. The experiment can
hardly be regarded as conclusive until experiments with *
more concentrated systems are undertaken.
Coupling the above observations with the syneresis
results suggests that if a soap-oil phase is present in the
dilute systems, that it must be relatively rich in soap if
it remains unchanged on quenching. Such reasoning would
lead to the conclusion that phase B of a tentative calcium
stearate-cetane phase diagram (27) does not exist in the
postulated range, or it is necessary to assume that on
quenching, phase B undergoes decomposition to one of the high
temperature forms of pure calcium stearate, which in turn
supercools, plus liquid cetane. Present X-ray data are not
conclusive on either possibility.
Further visual data which may be useful in resolving
this problem are afforded by the behavior of anhydrous cal
cium stearate with other solvents, d-2-ethylhexyl sebacate
and ethylene glycol. The swelling and clearing occurred at
about the same temperature in these systems as in the
138
cetane system. The sebacate system appeared reasonably
homogeneous to the eye, like the cetane system, but the
glycol system very evidently contained two phases. Evi
dently, a liquid in which hydrocarbon groups predominate
allows a greater dispersion of soap than a liquid in which
the polar groups predominate.
In fact, in all systems studied which contained cal
cium stearate, the temperature at which transformation from
slurry to either stiff or fluid, translucent mass occurs,
is in a very narrow range from about 105° to 125° in dilute
soap systems.
In addition to the observations of the temperature
of clearing are those concerning the relative viscosity of
the various systems studied. Particularly significant is
the suggested connection between viscosity at the higher
temperatures and syneretic tendency.
Water, stearic acid, methanol, acetone, a-tetralone,
nitroethane, diethylene glycol, n-heptanol, di-n-butylamine
are all effective in the prevention of syneresis, and all
reduce the viscosity of calcium stearate-cetane systems
above the clearing point. An 18$ calcium stearate-2^
stearic acid-cetane system observed between crossed polar-
oids was isotropic, both at rest and when flowing.
Compounds which were ineffective in the prevention
139
of syneresis were also ineffective in reducing the viscos
ity of calcium stearate-cetane systems above the clearing
point. Esters such as methyl stearate, amyl acetate, and
di-2-ethylhexyl sebacate proved to be ineffectual. Nitro
benzene, too, fell into the same category as the esters.
Evidently, then, mere polarity is not the criterion for a
useful additive, since all compounds tried were polar in
nature, the nitrobenzene especially so.
It is of interest to note that all compounds which
proved effective in the prevention of.syneresis and which
yielded relatively fluid, isotropic solutions above 115°*
are those in which hydrogen bonding occurs or can conceiv
ably occur. Visual evidence alone, of course, is insuffi
cient to demonstrate that the stabilizing effect is connect
ed with such a property, but the results are highly suggest
ive that such a relationship exists.
Although it is indicated that pyridine also was some
what effective in preventing syneresis of quenched systems,
there is some doubt that the pyridine was completely dry at
the time of use. Pyridine is known to be highly hygroscopic,
■and although the pyridine was initially sold as the dry
reagent and the bottle kept tightly stoppered, it is pos
sible that enough water may have been present to invalidate
the results.
The behavior of pyridine-containing systems was
considered sufficiently important to warrant additional
investigation, which was concluded after the main portion
of the thesis had been written. The Fischer reagent EK
! pyridine was dried over NaOH and distilled. Comparison of
i
the refractive index of the distillate with refractive
indices of pyridine-water systems given in the Internation- ;
al Critical Tables indicated that the product was at least
98$ pyridine, substantially water free.
An 18$ calcium stearate-^. pyridine-cetane system
behaved in a manner similar to that already recorded for the
other pyridine-containing systems, and yielded a slightly
,translucent, "wet" appearing, but non-syneretic mass on
quenching from 155°. Evidently, then, pyridine constitutes
an exception to the relation between compounds effective in
1 j
preventing syneresis and compounds capable of forming hydro
gen bonds.
The results of the visual observations of the lithium
1
stearate systems bears out the calorimetric and X-ray data
for such systems, which indicate that lithium stearate and
cetane are inert toward each other except at elevated ;
temperatures (above 175°) and the lithium stearate and
lithium stearate-cetane phases undergo complete reversion
to crystalline lithium stearate, regardless of the cooling
CHAPTER V I
INTERPRETATION OF THE X-RAY DIFFRACTION PATTERNS
Calcium stearate-cetane, H-l47. The purpose of this
run was to demonstrate that the liquid extracted from an
anhydrous soap-oil system in the manner described in page
20 did not represent all the liquid present as such in the
anhydrous system.
The system, originally 44.6$ soap, lost 29.5$ of its
weight as liquid, standing in a closed tube for one week
and in an open tube for one week. The cetane halo is clear
ly present in the pattern, although of rather low intensity.
The soap pattern is sharp, in contrast to the indis
tinct type of pattern obtained with anhydrous systems run
immediately after preparation. The sharp pattern would in
dicate that some crystallization has taken place during
standing. The long spacing is of the order of magnitude
expected for anhydrous solvent-free soap of comparable
thermal treatment.
The short spacings, however, are somewhat confusing. '
i
They do not correspond exactly to any found at room tempera
ture, being somewhat larger, which is to be expected if the
effect of quenching from high temperatures is to freeze in
the high temperature form, in which the molecules are
142
displaced from their positions in the well ordered crystal.
The 4.26 and 3*97 lines might correspond to such a situa
tion.
However, there are indications that in addition to
anhydrous soap, the hydrate might have been present to some
extent. To the right of the sharp short spacing peaks is a
region of the curve which is clearly above the base line but
running parallel to it. It is possible to select two peaks
of 3«57 and 3-40 A., neither of which is clearly resolved,
but which are only indicated by the fact that the curve lies
distinctly above the base line. The 3*40 line corresponds
to a hydrate line.
If the hydrate is present in the originally anhydrous
sample, its presence can be explained most likely in terms
of the existence of the pseudo-glass, form Vl'i in the sample
as originally quenched. This form readily absorbs water
from the atmosphere to form the hydrate (29). The recrys
tallization of the anhydrous soap to give a sharp hydrate
pattern is known, but not under the conditions of formation
of the present system; i.e., quenching anhydrous soap from '
260° would not give VI-A or VT-H forms.
The possible existence of hydrate in a sample ori
ginally prepared as anhydrous can be explained as above and .
suggests that some of the soap in the original quenched
143
system existed as pure soap because it showed the behavior
corresponding to pure soap. The present results, however,
do not preclude the possibility of the existence of a sol-
vent-soap phase.
Calcium stearate-stearic acid, M-56, m-43, M-47,
M-42. M-51, C-l. In order to investigate the possibility
of compound formation or solid solution in soap-acid mix
tures, a series of soap-acid mixtures were prepared and
their X-ray patterns were determined.
M-66, 1 mol CaStrp, l/B mol HStr. The pattern for
this system resembles the anhydrous calcium stearate pattern
when the soap is quenched from 155°• The long spacings are
similar, 50.2 A. in this system, 49.7 A. in an anhydrous #1
calcium stearate (29) quenched from 155°, but clearly not
identical. The difference may result from the difference in
purity of the two soaps, but there are no X-ray data avail
able at present on the #5 soap given comparable thermal
treatment.
There is a wide halo centering at 4.22 A., which is
slightly different from the 4.18 A. halo in the #1 soap
quenched from 155° (29)* No lines attributable to stearic
acid in any of its forms are seen.
M-43, 1. mol CaStrp, 1/4 mol HStr. The long spacing ;
; 144
corresponds to a calcium stearate long spacing. No long '
I i
■ spacing indicative of stearic acid is to be found. j
! The short spacings evident are 4.18, 3-97 (present 1
as a shoulder), and 3*62 A. These spacings resemble closely
I
' those of the #1 soap quenched from 135° (29). Other short |
, I
i spacings evident are at 2.50, 2.36, 2.23, and 2.11 A., all j
1 of which are identical with those found with #1 soap j
jquenched from 135° (29).
! The short spacings are relatively sharp and of high :
| |
' intensity, indicating a high degree of recrystallization of j
the soap even on quenching from the high temperature, in j
■ distinction to the result of quenching the pure soap from
such a temperature. Pure calcium stearate quenched from
155° yields VI-N or VIM patterns (29).
i
p i
M-42, 1^ mol CaStrg. 1_ mol HStr, quenched from 155°. ;
The long spacing characteristic of calcium stearate is quite!
! 1
iweak, but resembles that of the #1 soap quenched from 135°* 1
t
Another long spacing indicative of the 39-5 A. form of !
;stearic acid is also present, although very weak. j
j J It will be useful to tabulate the short spacings of 1
! 1
the quenched 1:1 molar ratio soap-acid mixtures along with 1
i . i
1
those of the #1 soap and principal stearic acid side spa- ;
cings which result from various treatments. Table XXVII j
irecords the calcium stearate and calcium stearate-stearic '
145
TABLE XXVII
SHORT SPACINGS OP CaStr2 #1 AND CaStr2-HStr
SYSTEMS OF VARIOUS TREATMENTS
Soap System and Treatment
#1, dried at 105°
#1, quenched from 135°
1 mol #5 CaStr2, 1 mol HStr,
quenched from 155°
#5, dried at 110°
1 mol CaStr2 #5, 1 mol HStr,
cooled slowly from 200°
Spacing (A) Intensity i
4.14
47
3.92
7
3.67
11
4.14 48
3.93
6
3.69 15
4.18 74
3.97
shoulder
3.62
3
4.41
25
4.15 27
3.91
6
3.67 2
3.42
7
4.49 29
4.l6 22
3.93
38
146
. acid data, while Table XXVIII is compiled from the data of
Grandine (14).
The peaks in sample M-42 were quite sharp. The short
spacings were very nearly those of the #1 soap, both dried
at 105° and quenched from 135°• It is also to be noted that
the spacings are those of the purest soap (cf. especially
4.4l and 4.14 lines for comparison), although the soap was i
the #5, a less pure preparation. It should be mentioned
that the #5 soap differed from the #1 and #4 preparations in
its behavior on drying at 1 1 0 °. The #1 and #4 soaps re
verted to an anhydrous pattern on drying to constant weight
at 1 1 0 °. The #5 soap, however, showed no change in its X-
ray pattern on drying, retaining the hydrate pattern after
losing its water of hydration.
Evidently the stearic acid present Induced a much
.greater degree of recrystallization than the calcium stear
ate by itself on quenching from the same temperature. The
soap pattern is similar to the VI-A rather than the VT-N i
pattern (28) generally obtained on quenching the solvent-
free soap.
M-47, 1^mol CaStrg, 1/2 mol HStr. The long spacings
are the same as those in the 1/4 mol HStr, 1 mol CaStr2
system, but slightly asymmetrical, as though there might be
shoulders present. The short spacings are those of the 1/4 ;
TABLE XXVIII
PRINCIPAL SHORT SPACINGS OF HStr FORMSa
Long Spacing
! A3.87b AQ.26C 4Q.I8d AO.59. U3.59)6 39.64f 39.48. 43.63g 40.17. 44.31
d/n I d/n l/ll4 d/n 1/59 d/n l/86 d/n 1/139 d/n l/ll6 d/n l/84
i ^55
4.50 0.11
4.46 .12
4.19 1.0 4.18 1.0 4.20 0.63 4.16 0.26 4.14 .15 4.18 1.0
4.26 S
4.12 S
3.97 S
3.79 S 3.81 0.16
3.75 .49 3.75 .58 3.73 0.50 3.71 .11 3.75 .82
: 3.34 0.10 3.38 .13
I 3.34 .16
3.07
M
3.02 M
2.96 M
2.90 M
2.89 .14
2.90 M
2.87 .15
i2.83 M
2.76 M
2.54 .11
I
2.50 .18
2.45
t
M 2.46 .09
£
-si
TABLE XXVIII (continued)
PRINCIPAL SHORT SPACINGS OF HStr FORMS3
Long Spacing
1 43.87 40.26c 40.18° 40.59,
± 42*52l!
39.64 39.48, 43.638 40.18. 44.31*
d/n I d/n 1/114 d/n 1/59 d/n 1/86 d/n 1/139 d/n 1/116 d/n l/84
2.42 M
2.30
.14 2.29 0.07
i
2.27 .20 2.27 0.17 2.26 0.18
2.27 .10
2.22 M 2.23 .11 2.24 .15 2.22 0.23 2.23 .13
1
1
2.22 .10
2.13 M
2.05 i f 2.03 0.20 2.03 0.24 2.02 .48
1
2.01 0.16 2.00 0.29 2.01 .49
Total Lines Rep * t.
31
11 19
18 21
24 15
i
Lines Classed Strong
115 3 6 8 6
13 4
3 The total number of lines reported as short spacing is recorded below the figures and compared with ,
i the number of lines classified as strong in the table so that some idea as to the number of remain-
t ing lines which are classified as weak can be gathered. Strong lines reported are those whose rela-
' tive intensities (l/l0) are greater than 0.1. Literature lines are reported if they are strong (S) ;
^ or medium (M).
■ Literature values: Francis, Piper, Malkin, Proc. Roy. Soc. A 128. 214 (1930)J Muller, Proc. Roy.
I Soc. A 114.542 (1927)j Schoon, Z. physik, Chem. B 39. 385 (1938).
9 Melted sample poured into agate mortar at room temperature,
f Saturated ethanol solution poured into three volumes of water at room temperature.
9 Ether solution allowed to evaporate at room temperature.
f Crystallized from ethanol solution at 50° 0. M
8 Crystallized from ethanol solution at 5° C.
“ (VI) ground in mortar. - - -
mol HStr, 1 mol Castrg system and are comparable in sharp
ness. No HStr lines are present.
M-51* 1. mol CaStrp , 1 mol HStr, slow cooled from
200°. The pattern for this system shows two clearly defined
long spacings, 43.6 A ., corresponding most nearly to the
44.3 A. form of stearic acid (14), and 49.5 A ., indicative
of calcium stearate. The stearic acid spacing is one and
one-half times as intense as the soap spacing.
Short spacings present are at 4.49, 4.16, 3.93* and
3.71 A. The 4.49 line may correspond to the 4.4l line of
the soap dried at 110°. The 4.16 line matches both stearic
acid (40.0 A. form) and calcium stearate (#1 and #5); 3-93
A. is a spacing found also in both preparations of calcium
stearate, but is more intense here than in the soaps by
themselves. This line also appears in the quenched 1:1
system in about the same intensity. The 3.71 line is prob
ably due to the acid since it is the strongest short spacing
found in the 44.3 A. form of stearic acid (14).
The data indicate that slow cooling allowed the 44.3
A. form of stearic acid to crystallize independently of
calcium stearate, which itself crystallized as it does when
slowly cooled alone. It is possible that some stearic acid
might have crystallized with the calcium stearate because of
the somewhat larger value for the 4.4 A. line (4.49 A.),
150
although this interpretation depends upon the assumption
that the two lines sire from the same pair of scattering
points.
0-1, 1 mol OaStrg,, 2 mol HStr, slow cooled from l6Q°.
Three sets of long spacings were picked out of the pattern
of this system. 46.5, 43*3, and 39*6 A. lines were all
present, although the 46.5 and 39*5 lines were of very low
intensity and the 43.3 line was of very high intensity.
The very short spacing of calcium stearate here is similar
to that found with the very impure Metasap soap (27) on
cooling from 200°, 47.3 A.
A number of short spacings occur in the pattern.
These lines are 4.55, 4.40, 4.15, 3.85, 3-74, 3-56, and
3.33 A. The 4.55 line appears to be a single line. Although
the 4.55 line appears to correspond with the 43 A. form of
stearic acid, the intensity of the 4.55 line is much greater
in the present system than it is in any of the pure stearic
acid patterns in which it appears. The 4.15 line could be
due to both soap and/or acid. A weak intensity 4.03 line
is probably due to stearic acid (14). The 3*85 line is due
to 43.6 A. stearic acid and is very prominent. The 3*58
line might be identifiable with the 3*82 line of the slow
cooled 1:1 system, although neither line matches exactly one
found in stearic acid or calcium stearate forms. The 3.33
151
lin e is p robably to be id e n t if ie d w ith s te a r ic a c id .
The v e ry s h o rt spacings, about 2 to 2 .5 A ., are the
same as those found w ith #1 anhydrous, s o lv e n t-fre e calcium
s te a ra te d rie d a t 110° .
Again i t appears th a t slow c o o lin g has allow ed sepa
r a te c r y s t a lliz a t io n o f soap and a c id to proceed, as in the
p reviou s slo w ly cooled system. The r e la t iv e amounts o f acid'
and soap are re ve rs e d , o f course. Although both a c id and
soap have c r y s t a lliz e d s e p a ra te ly , the p o s s ib ilit y o f a c id -
soap in te r a c tio n is n o t precluded beeause o f th e occurrence
o f sh o rt spacings not id e n t if ie d w ith e ith e r soap or a c id in
any form known in the pure s ta te .
G eneral d iscu ssio n o f re s u lts w ith C aStrg- H S tr
Systems. The 1 /8 mol H S tr, 1 mol CaSti?2 system p a tte rn
appears alm ost th e same as th a t o f the pure soap tre a te d in
th e same manner. On in c re a s in g the s te a r ic a c id co n ten t,
however, the sharpness o f the lin e s in c re a s e s , in d ic a tin g a
g re a te r degree o f c r y s t a lliz a t io n , p robably caused by the
presence o f the s te a r ic a c id . The pure soap appears to have
c r y s t a lliz e d in the 1 /4 mol H S tr, 1 mol C aStr2 system, w ith
no s o lid s o lu tio n o r compound fo rm a tio n in d ic a te d .
The quenched 1 /2 mol H S tr, 1 mol C aStr2 and 1 mol
H S tr, 1 mol C aStr2 systems gave v e ry n e a rly the same p a t
te rn s , which leaves a p o s s ib ilit y o f s o lid s o lu tio n , b u t
152
which probably rules out compound formation because of the
'existence of the pure soap pattern in the 1 mol HStr, 1 mol
Castr2 system.
>
t
It is possible that the presence of stearic acid with'
;the soap brings about a greater degree of crystallization of
the soap system on quenching simply by its action of increas
ing the fluidity of the soap system and allowing greater i
I
freedom of motion of the soap molecules in rearranging them
selves into the low temperature crystal form from the high
I
;temperature form.
Slow cooling in both the 1 mol HStr, 1 mol CaStr2 and:
,2 mol HStr, 1 mol CaStr2 systems appears to have the effect .
of allowing at least part of the acid to crystallize inde-
i
pendently of the soap, whereas quenching either prevents
I
such crystallization or weakens the intensity of any acid
|lines so as to render them unobservable.
M-49, 17.5# CaStrg, 2.1# HStr. 80.4# Cetane. This
system is at the composition found to have a maximum pres- :
sure stability and corresponds to a molar ratio, soap to
acid, of 4.2 to 1. The long spacing is about 51.5 A.,
indicating CaStr2. It is of a very much weaker intensity
than the short spacings and is longer than that found in
the solvent-free systems. There is no long spacing for the J
stearic acid. !
153
The prominent 4.17 A. spacing may be the 4.185 A.
line in the anhydrous 22.9$ calcium stearate-cetane system
quenched from 130° (30). The 3*77 A. line hlso present in
this system is probably comparable to the 3.7-3*9 line re
ported in the 130° anhydrous soap-cetane quenched system.
A 2.2 A. line present in this system is absent in the anhy
drous soap-cetane quenched system of similar composition.
M-50. 18.0$ CaStr0. 5-9$ HStr. 76.1$ cetane. The
entire pattern of this sample was almost identical with that
of the previous sample, even to intensities of long and
short spacings and to the cetane halo, which is clearly
evident.
The intensity and sharpness of the lines in the
present pattern and the one preceding is more nearly com
parable to systems of similar composition, but without the
stearic acid, slowly cooled from 170° in the anhydrous sys
tems. Evidently the stearic acid in both systems induced or
allowed a greater degree of crystallization to occur on
quenching than that which generally occurs in quenched anhy
drous systems. The absence of stearic acid lines is as yet
unexplained, but is highly significant.
The virtual identity of this pattern with the one pre
ceding, in spite of the differences in physical behavior and
pressure stability behavior, leads to the supposition that
154
the crystal structure In these two systems is virtually
identical. Any differences in particle shape or size can
not be detected by the present apparatus.
Calcium stearate-methanol-cetane, S-40, C-2, Sr4l.
The diffraction pattern of the soap appears to be much
sharper in all these systems than in comparable non-additive!
calcium stearate-cetane systems of comparable thermal
treatment (30). The long spacing is about 50.2 in all pat
terns, comparable to the 71-A long spacing (28) of the anhy
drous soap. 1
The short spacings, however, cannot be connected with
certainty to any room temperature form, hydrous or anhydrous.
It is possible that the 4.17 (C-2), 4.16 (S-4l), and 4.17
(S-40) lines correspond to the 4.11-4.14 lines of the anhy
drous soap (30), the larger spacing being due to a looser
packing. The 3*71 and 3*76 lines (S-40,- Sr4l) may also
correspond to the 3*70 anhydrous line, following the same
reasoning.
The 4.42 (S-4l) and 4.52 (S-40) lines do not approach
any anhydrous line, more nearly approaching the 4.4 hydrate •
line. A 4.55 line which is observed in C-2 has also been
observed in certain calcium stearate hydrate-eetane systems j
1
(23) and a calcium stearate-stearic acid system (C-l). The
2.97 line (C-2) corresponds neither to hydrate nor anhydrous
soap.
It is seen that there is some uncertainty as to the
identity of the crystal form of the solid present in the
methanol systems. It can only be said that the solid phase
is relatively crystalline, although in S-40 and S-4l the
long spacings are rather indistinct.
Calcium stearate-water-Monoplex, C-3« A relatively
well-crystallized soap is present, and comparison with
hydrate-cetane systems indicates that the solvent used here
had no effect on the crystalline form of the soap except
:that possibly there is a slightly greater separation of
chains in the Monpplex solvent.
The 49-8 A. long spacing corresponds almost exactly
with the 49.7 A. spacing for the pure hydrate (27), while
the 4.42 and 4.17 lines have direct counterparts in the pure
hydrate also.
C-4t calcium stearate-n-heptanol. The long spacing
corresponds more nearly to an anhydrous spacing, which is
generally greater than 50.0 A., but which varies somewhat
(27).
However, the 4.38 line corresponds most nearly to a
hydrate line, such as 4.4 A. (27). The 4.15 A. line could
be either hydrate or anhydrous. The 3.42 A. line also
156
corresponds most nearly to a hydrate line, 3.4l A.
It would appear that the soap has crystallized in a
hydrate-type structures although the system was presumably
anhydrous when prepared and the system run immediately after
preparation.
Lithium stearate-cetane. Anhydrous lithium stearate-
cetane systems have been found to yield stable (non-syner-
,etie) greases, in contrast to calcium stearate-cetane sys
tems, which must be stabilized by water or other additives.
The X-ray diffraction behavior of some lithium stearate-
cetane systems of various treatments was studied. Some of
the data are recorded by Hattiangdi (15)* In addition, the
X-ray patterns of several solvent-free lithium stearate
preparations were obtained (27). Table XXIX summarizes the
information for the several systems.
Obviously there is virtually no difference in the X-
ray behavior of the lithium stearate systems, despite the
differences observed in the pressure stability behavior.
The lithium stearate has been very nearly crystallized in
its solvent-free form in all systems. The quenching beha
vior cannot be compared to that of the calcium stearate sys
tems, since all quenching temperatures used were below the
temperatures at which lithium stearate and cetane interact
appreciably (28). No compound with water is formed.
157
TABLE XXIX
X-RAY SPACINGS OF LiStr-CETANE SYSTEMS
Long Short
System and Run No. Spacing Spacing
Metasap LiStr, undried, E-48 39.9 4.23
4.01
3.97
3.73
3*58
2.36
2.28
Metasap LiStr, dried at 105°, H-55 40.0 4.23
4.01
3.97
3.73
3.58
2.37
2.28
Metasap LiStr, slow cooled from 200°,
H-8l 40.2 4.24
4.04
3.97
3.74
3.58
2.37
2.28
18$ LiStr-cetane, quenched from 155°, 40.6 4.23
H-180 4.07
3.77
3.63
4.66 cetane halo
24.6$ LiStr-cetane, residue of H-l80 40.7 4.24
after pressure stability run at 4.05
10 psi, H-181 3.79
3.63
4.66 cetane halo
158
TABLE X X IX (c o n tin u e d )
X-RAY SPACINGS OP LiStr-CETANE SYSTEMS
System and Run No.
Long Short
Spacing Spacing
18.0$ LiStr-cetane, slowly cooled from 40.6 4.26
2000, h-189
4.07
4.66
3-97
3-77 !
3.63 :
cetane halo
X X
27.5$ LiStr-cetane, residue of H-189 40.6 4.24
after pressure stability run at
4.07
10 psi, H-190
3.95
3.74
3.64
4.66 cetane halo
32.6$ LiStr-cetane-0.6$ H20, quenched
40.3 4.23
from 155°, after pressure stability 4.01
run at 10 psi, M-55
4.66
3.73
3.57
cetane halo
I
I
CHAPTER V I I
POSSIBLE INTERPRETATIONS OF VISUAL AND X-RAY OBSERVATIONS ,
I
On the b a s is o f v is u a l and X -ra y d a ta , i t is pos
s ib le to in d ic a te to some e x te n t under what c o n d itio n s non- '
s y n e re tic g e ls o f calcium s te a ra te -c e ta n e m ight be expected '
to fo rm . !
The X -ra y r e s u lts coupled w ith the syn eresis e x p e ri
ments on anhydrous calcium s te a ra te -c e ta n e systems in d ic a te ,
;th a t th e quenched n o n -a d d itiv e systems over a very wide
range o f com position co n sisted a t the tim e o f these e x p e ri- 1
ments o f p a r tic le s o f a quenched, or p a r t i a ll y quenched, ,
calcium s te a ra te mesophase which may or may not have con
ta in e d sm all q u a n titie s o f cetane suspended in liq u id cetan e.
The X -ra y re s u lts on a d d itiv e calcium s te a ra te -c e ta n e
i
systems suggest th a t calcium s te a ra te may b erp rese n t in a
i
s o lv e n t-fre e form , p o s s ib ly s lig h t ly m o d ified by the presence
o f cetan e; but the X -ra y d a ta cannot p erm it a choice between
s o lv e n t-fre e calcium s te a ra te m o d ified by cetane and a c a l- ’
eium s te a ra te c o n ta in in g sm all amounts o f d is s o lve d cetan e.
The absence o f d ata c le a r ly in d ic a tin g ex ten siv e
s o lu tio n o f cetane in calcium s te a ra te re q u ire s c o n s id e ra tio n
;o f p h y s ic a l s ta te o f soap p a r tic le s and p a r t ic le - p a r t ic le
in te r a c tio n . Some c o n s id e ra tio n o f s o lid systems r e ta in in g .
.s u b s ta n tia l- am ounts-of - liq u id ~ m ig h t_ b e --u s efu l in -in te r p r e tin g
: 160 '
the behavior of the present systems.
Silica-water, glass wool-water, and "coated" silica-
cetane as examples of solid-liquid systems. Probably the
simplest possible liquid retention mechanisms to consider in
a system composed of solid particles is one in which liquid
\
retention is due solely to the physical form of the particles
in creating spaces in which liquid is held by capillary
forces.
Toe?illustrate the large effects which might be en
countered and which depend largely on size or shape of the
- particles, three systems were examined.
A system, 75$ Fisher 2^0 mesh silica and 25$ water by
weight, was prepared. The solid particles were incapable of
retaining liquid. The particles settled rapidly, leaving a ■
supernatant suspension of fine silica particles in water.
Examination of the particles in the system with an optical ;
micrometer revealed particles having a variety of sizes. 1
Some were as large as 10”^ cm. in diameter, while the aver- !
age size was of the order of 10“3 cra. diameter. j
The 17$ Linde "coated silica 30"-cetane system was
coherent and retained its liquid despite the relatively low
concentration of solid. Examination of the solid particles
|
under the microscope (430X) revealed only bright pin points
of light and no particles which could be measured. A
i ' t
1 61
reasonable in fe re n c e is th a t the d iffe re n c e in liq u id
re te n tiv e n e s s is connected to the d iffe re n c e in p a r t ic le
s iz e .
The d iffe re n c e in b u lk in e s s o f the two s ilic a s was
n o ta b le . The F is h e r s i l i c a was a v e ry compact powder w h ile
the Linde s i l i c a was v e ry b u lk y , a given w eight occupying
many tim es the d ry volume o f a l i k e w eight o f th e F is h e r
s i l i c a .
It is known that the bulkiness of powders composed of
minute particles is very high, decreasing as the particle
size increases, becoming nearly constant at a partiele size
which depends on the substance (19). The large bulkiness
has been ascribed to electro-static repulsion between the
particles (19). It is possible that such forces accounted
for the difference in liquid retentiveness. In any event,
the difference can be ascribed to a particle size effect.
As an example to demonstrate the effect of partiele
shape, pyrex glass wool was soaked in water, allowed to
drain for five minutes, and the amount of water retained was
measured. It was found that the soaked glass wool-water
system consisted of 9^$ water by weight. Even after squeez
ing water out of the system by hand, the resultant system
contained 80$ water by weight. The difference in liquid
retentiveness between this system and the others may be
162
la r g e ly due to the d iffe re n c e In shape o f p a r tic le s , the
g la ss fib e r s being a b le to hold la rg e amounts o f liq u id in
an ex ten siv e pore system.
P o ss ib le fa c to rs in a d d itio n to p a r t ic le form in the
p re v e n tio n o f syn eresis o f calcium s te a r a te - cetane system s.
A complete d iscu ssio n o f mechanisms o f liq u id re te n tio n in
the p res en t s o a p -o il systems cannot stop w ith the sim ple
p h y s ic a l e x p la n a tio n suggested by th e experim ents w ith the
s i l i c a systems.
Two g e n era l phenomena p res en t them selves as p o s s ib le
i
a d d itio n a l s t a b iliz in g mechanisms, (1 ) p a r t le le - p a r t ie le
in te r a c tio n , such as cementing o f p a r tic le s to form a r e l a
t iv e ly r ig id , porous s tru c tu re , or re p u ls iv e fo rc e s which
p reven t clo se c o n tac t o f p a r tic le s , and (2 ) liq u id - p a r t ic le
;in te r a c tio n , such as ad s o rp tio n which f ir m ly binds liq u id
to p a r tic le s and p reven ts i t s escape, o r in t e r f a c ia l te n
sio n , which determ ines the magnitude o f c a p illa r y fo rc e s
ten d in g to b in d masses o f liq u id in c a p illa r y spaces.
P a r t ic le - p a r t ic le in te r a c tio n . The p o s s ib ilit y o f
e le c tr o s ta tic re p u ls io n between soap p a r tic le s is n ot to be
(overlooked in view o f the o b s ervatio n o f t r ib o e le c t r ic
e ffe c ts in both hydrous and anhydrous systems o f calcium
s te a ra te in cetane (2 3 , 2 9 ).
However, such effects are noted only at quite high
soap concentrations, above 58$ calcium stearate in the hy
drate system and about 75$ soap in the anhydrous system.
The effect appears to be a chance one, since it is not
always observed in these systems (23). No such effects have
been detected in dilute soap systems.
The opposite type of effect, cementing of particles,
will depend upon the nature of the particle surfaces. In
the soap systems, (C00)2Ca and methyl (or methylene) groups
will constitute the surface. The surface will consist of
about 10$ polar groups.
Interparticle cementing through contacts between non
polar parts of the surface will probably play little or no
part in a cementing process, primarily because any such con
tacts could be broken easily by solvent molecules in thermal
motion.
The polar groups which are in different particles,
but which come into contact, may be held by forces which
approximate the ionic forces in the soap crystal. However,
the difference between additive and non-additive systems
must be explained, since at first appearance, the ratio of
polar surface to non-polar surface can be expected to be
about the same in both cases.
The possibility of bridging between particles by
164 .
additive molecules is not to be overlooked. Again, the
points of contact would probably be the exposed polar groups,
i
with the molecule acting to Join the two groups. However,
if the principal effect of additive in the solid-liquid
system is to bridge, it would seem at first sight as though
increased additive should give a firmer structure. The
results with the stearic acid and methanol additive systems ;
do not bear out that supposition.
Liquid-particle interaction. Adsorption of solvent
t
on the particles is possible, but since the forces would be
largely van der Waals forces, it might be expected that
adsorbed solvent would not be held tenaciously. Calculation
based on the assumption of spherical particles 10"5 cm. in
diameter and molecules 20 &2. cross section shows that less
than 5 per cent of the solvent could be held in a mono-
molecular layer in a 20$ soap system under such circum
stances .
If capillary forces are at all responsible for liquid
retention, interfacial tension between liquid and solid
particles will be of utmost importance. An attempt was made
to prepare samples of calcium stearate and calcium stearate
hydrate quenched from 155° for measurement of contact angles
with cetane. However, no satisfactory surface could be pre
pared, but it was observed that both hydrous and anhydrous
jsoap were readily wet by cetane. !
! !
I Regardless of what factors considered above may be j
joperative in stabilizing the systems against liquid loss, j
t i
!it is readily appreciated that a large surface to volume !
' t
j
|ratio of the solid particles will favor the operation of i
i I
I such stabilizing factors. J
i ;
One possible role of additives in preventing
i
[syneresis♦ Despite the number of mechanisms it is possible j
i to advance to account for the difference in the liquid
i
I retentiveness of non-additive and additive systems, no set
j
iof data as yet exists which will allow a choice to be made,
;or in fact, whiGh even indicates the existence of such j
I !
|factors. j
f Particle shape and small particles (large surface to j
1 ^ i
I volume ratio) have been stressed in all previous discussions'
i I
i >
las probably favoring stability against liquid loss. It is j
! I
I of interest to note that all non-synerqtic grease systems j
j examined by the elec tron microscope reveal the presence of j
i l
!fibrous soap particles, several times longer than wide. All!
isyneretic systems appeared to be shapeless blobs of uncer- |
! • . . . . . |
itain size (5, 9, 2^, 3)* Birdsall and Farrington (3) also i
|commented on the presence of fibers in non-syneretic systems'
and their absence in syneretic systems. j
Aside from the differences in the syneretic and j
166
non-syneretic systems at room temperature which have "been
noted, the present investigation has brought to light
another relation, not generally commented upon in detail in
discussions of grease systems. The present visual observa
tions reveal that calcium stearate-cetane systems which were
non-syneretic on quenching from temperatures above 120° were
isotropic and fluid above that temperature, while systems
which were extensively syneretic when quenched from above
120° were much more viscous, in some cases very stiff, and
at least in the case of non-additive systems, somewhat
anisotropic. The only exception to this case was the cal
cium stearate-caleium acetate monohydrate-cetane system.
X-ray diffraction patterns reveal that for the most
part, the soap in non-syneretie systems is more nearly
crystallized than that in syneretic systems, at least short
spacings are sharper and more distinct in non-syneretic
systems.
Finally, the observation is made that evidently only
a rather select class of compounds appear capable of sta
bilizing the calcium stearate-cetane systems against syner-
esis, namely, those in which hydrogen bonds occur or can
occur.
These three observations form the basis of a hypothe
sis of one possible (not necessarily the only) way in which
I
| additives act in calcium stearate-cetane systems. It is
assumed that the presence of additive allows the soap to
pass into solution in the solvent where it would otherwise
transform into a liquid crystal state.
It is necessary to have detailed information about
the crystal structure of the soap in order to explain satis
factorily the action of hydrogen bonding in bringing about
solution. However, it is reasonable to assume that the
bonds between calcium ion and the carboxyl oxygens are
electrostatic. According to Zachariasen (32), the carboxyl
groups are probably in a resonance state, since a uniform
C-0 distance of 1.27 A. was observed with sodium formate,
and the carboxyl groups are planar.
The electrostatic bonds from the calcium ion are
probably distributed among several oxygens. The calcium ion
can coordinate either six or eight oxygens, how many here
is not known. Pour oxygens can be supplied by the soap
anions of the calcium ion, but the remainder must come from
adjacent molecules. It might be this state which gives the
calcium stearate crystal its stability compared with the
acids or the hydrocarbons.
The action of a hydrogen-bonding substance might be
in forming a hydrogen bond between the additive molecule and
a carboxyl oxygen, thus nullifying the attraction between
168
that oxygen and the calcium ion of an adjacent molecule.
By such a mechanism the soap crystal might be destroyed and
solution brought about.
It is true that the ketones and nitroethane must be
transformed into tautomeric forms, enol for the ketone, aci
for the nitroethane. Such transformations require energy.
Adkins (1) reports the energy of enolization of certain sub
stituted ketones to be of the order of 1-2 Kcal/mole and
further.comments that enolization is favored in inert sol
vents such as hydrocarbons. The energy of hydrogen bond
formation is of the order of 3-10 Kcal/mole, so that a
cursory consideration of energies makes enolization appear
feasible. A possible further driving force for the process
might arise in a gain of entropy of solution of soap mole
cules in the hydrocarbon.
That some strong interaction is taking place, at
least in some instances, is indicated by the fact that the
methanol systems did not behave like the stiff, non-additive
calcium stearate-cetane systems even at 155°, whereas the
boiling point of methanol lies far below such temperatures.
On quenching, the soap appears to be freer to form
the room temperature crystalline form rather than a quenched
mesophase. No data exist as yet to connect the crystal
form, particle size, and particle shape with the state of
169
the system at higher temperatures.
The ease of calcium aeet&te action seems a rather
special one. The action of calcium acetate in stabilizing
calcium soap greases may be pictured, to be far. different in
nature than the action of the other additives. A similar
action is observed in the case of barium soaps, which are
stabilized against liquid loss by barius acetate. In the
barium soap-barium acetate systems, it is concluded that the
’ 'complex" formed between the two substances is not a
stoichiometric compound (31)* In addition, the X-ray dif
fraction pattern shows spacings not identifiable with either
component alone (31)* Aside from such information, little
else appears to be known about such combinations.
As a suggestion of possible action, it might be con
sidered that the acetate molecules can be sandwiched in
between stearate molecules when a high enough temperature is
reached. This sandwiching might be pictured to stabilize a
liquid crystalline phase by allowing the stearate chains
room to execute considerable, motion. At the same time, the
polar planes of the complex may not be far different from
the polar planes of the pure soap, so that the acetate mole
cules might tend to join stearate molecules together to form
sheets, where the stearate molecules by themselves might
break off into clusters due to the agitation of the closely
packed stearate-chains. The extensive association-of -the
complex which is postulated might account for the extreme
stiffness of the complex at high temperatures.
It is an additional consideration to presume that
solvent molecules might be able to sandwich themselves in
the spaces between separated stearate chains, but it must
be considered that such sandwiching would seem to destroy
the purpose of the aeetate, namely the separation of the
stearate chains for greater freedom of motion.
CHAPTER V I I I
CORRELATION OF PRESSURE STABILITY RESULTS
WITH POSSIBLE GEL STRUCTURES
The visual and X-ray evidence has indicated only that
the gels of calcium stearate and cetane consist of a soap
phase, or possibly a soap phase with small amounts of dis- ,
solved liquid, and that stabilization against syneresis by
the presence of soap-oil phases such as suggested by Doscher
and Void (8) does not appear likely.
To account for the difference in liquid retentive
properties of additive and non-additive systems, the im
portance of particle size and shape was emphasized. The
geometry of the system then assumes an important role.
Geometrical considerations. A collection of spheres
represents in many cases a satisfactory approximation to the
state of packing of a powder or porous material.
Hexagonal close packing of spheres gives a free
volume of only 25$ in which liquid can be accommodated.
Cubic packing of spheres gives a free volume of 48$ based on
the total volume of the system (22). In neither case does
the result depend upon the radius of the spheres, although
in actual practice the porosity is found to increase with
decreasing particle size (22). Cubic packing is the more
172
unstable arrangement of spheres, and spheres in that ar
rangement will tend to assume the stable hexagonal packing.
Actually, most porous materials do not consist of
spheres, with the result that particle interference can ocaur
and the most stable arrangement lies between the cubic and
the hexagonal packing, between 25$ and 50$ void space. It
is interesting to note the results of the syneresis of the
anhydrous calcium stearate-cetane systems in this respect.
Prom Table XXV the porosity after syneresis is much greater
than either cubic or hexagonal packing of spheres, while the
final porosity after extraction of liquid with filter paper
is between that of cubic and hexagonal packing of spheres.
With respect to retention of liquid in pore spaces,
it can be seen that the radius of the tiny spaces between
spheres must be small enough to form a network of capillaries
in the sphere system capable of retaining liquid by capil
lary forces and preventing rapid flow of liquid from the
system. A small particle size will be more effective in
this respect.
Anisodimensional particles afford the greatest
'opportunity for structures with large free volumes. As an
example, the fractional free void space in a system of rec
tangular parallelopipeds arranged in an open network, like
a three dimensional weave, can be roughly calculated.
173
If the ratio of thickness to length is n, for small n
it can he shown that a good approximation to the fractional
void space is given by
(1-n)3 + n2
For:n = 0.05, fv = 0.99# while if n = 0.10, fv =
i
O.96. Of course, a system of fiber type particles formed in
a haphazard manner will probably show no such behavior. But
it is possible for such anisodimensional particles to become
entangled and leave very large void spaces. The strength of
the structure will depend upon the extent of the entangle,-
ments and/or the strength of the contacts.
With respect to the present systems, fiber-like par- .
tides may be formed in two ways, either by direct formation
of crystals in the shape of fibers or needles, or by the
building up of chains of relatively spherical particles.
Present electron micrographs appear to indicate the former ;
(3).
Effect of preparative conditions on pressure stabil
ity. Any system which is composed of a large number of
minute particles of different sizes and shapes can be
expected to vary considerably in its properties, depending
upon the preparative conditions. The experience gained in
174
achieving reproducible results would indicate the sensitive
nature of the present systems on preparative conditions and
suggest that certainly a part of the reason lay in the above
dependence.
Present data do not permit a clear distinction between
differences in pressure stability caused by different size •
and shape of particles, and differences caused by difference
in degree of reversal of possible phases present in high '
temperature systems.
Composition dependence of pressure stability. The
results of Table VI, showing the dependence of pressure
stability on soap content, are those expected for a situa
tion in which the ability to retain liquid depends primarily'
upon the quantity of solid present in the system.
Below about 18$ calcium stearate the loss versus
composition curve is extremely steep, indicating a con
siderable dependence of pressure stability on soap content,
but beyond 18$ soap the dependence is much less. Evidence
from other methods does not clearly indicate at present
whether the change in behavior on passing 18$ soap should
be regarded as an indication of some new stabilizing mech
anism (23).
It might be expected that the composition-loss
dependence would be marked, since the effect of solid is
175
twofold: (l) to provide a rigid structure, and (2) to pro
vide the capillary spaces to hold the liquid.
Effect of time of standing on pressure stability.
The number of experiments with this variable are not exten
sive, and therefore, general conclusions cannot be drawn.
It is apparent from Table XII that systems allowed to stand
i
for periods up to two weeks undergo no change in pressure 1
stability, although the initial loss rate appears to in
crease somewhat. This behavior may be interpreted to indi
cate that no structure was built up or destroyed while the
systems stood quietly and that the structure responsible for'
the pressure stability was formed immediately on quenching.
1
Effect of additive content on pressure stability.
Present X-ray data (23) indicate a progressive decomposition
of hydrate on increasing temperature in calcium stearate
monohydrate-cetane systems. Effect of excess water might
be expected to favor reformation of hydrate on quenching.
Pressure stability data indicate a decrease in pressure
stability on increasing the water content of calcium
stearate-water-cetane systems bpyond the monohydrate compo- ;
sition.
X-ray data show that small excesses of water appear
to have no effect on the diffraction patterns of quenched
176
systems. Evidently then,.water is complex in its action in
these systems, but its complete role is not yet clear.
The effect of varying the quantity of stearic acid
and methanol in calcium stearate-cetane systems is very
striking, but the cause is not made clearer by the magnitude
of the effect. The X-ray results (M-^9, M-50) further in
crease the puzzle, since systems of opposite pressure sta- j
bility behavior gave patterns which were almost identical;
one system gave the smallest liquid loss, while the other
gave the greatest liquid loss under pressure.
The non-syneretic nature of the very soft stearic
acid systems would appear to be somewhat contradictory to
expectation if the existence of a more or less rigid struc
ture formed by particle-particle contacts were essential to
the stabilization against syneresis.
A possibly interesting observation is that initially
soft systems which are quenched (18$ calcium stearate-5*0$
stearic acid-cetane, for example) can be worked vigorously
with a spatula and yet retain a yield value, since a tube of
material so treated will not flow when tipped. On the other
hand, a system of the same composition, when slowly cooled
from a temperature at which the system is fluid and iso-
tropie, yields a fairly firm, but "wet" appearing mass at
room temperature. The system is non-syneretic on formation
177
and exhibits a yield value. However, vigorous working
causes destruction of whatever structure is responsible for
the yield value. After the working, the system flows like
a thick suspension when the tube is tipped. The original
stiffness does not return on standing.
The foregoing observations suggest that a direct
microscopic investigation of such systems may prove fruit- ;
ful in determining the structure of the room temperature
gels, since if working does not bring about drastic changes
in particle size and shape, additional factors in the pre
vention of syneresis will have been substantially demon
strated.
Pressure stability of lithium stearate-cetane systems.
The lithium stearate-cetane systems afford the most conclu
sive evidence for the presence of solvent-free crystalline
soap in a non-syneretic. grease system. All liquid is
present as such.
Water in the lithium stearate-cetane system appears
to have decreased the pressure stability, in spite of the
presumably inert character of water in such systems. The
result was duplicated, and is thus no artifact.
The difference in pressure stability between the
slowly cooled 18$ lithium stearate-cetane system and the
I
quenched 18$ lithium stearate-cetane system is interesting.
178
The slowly cooled system was allowed to cool continuously
\
from 200° to room temperattire at about 0.5° per minute. The
quenched system was allowed to cool slowly from 200° to 155°
at about the same rate, where it was held one hour before
quenching. Solid crystalline soa£> is formed in both systems
during the slow-cooling process in both instances.
The principal difference between the two systems may
not have been the quenching versus slow-cooling treatment,
but rather the difference in the length of time the quenched
system was maintained at 155° compared with the slowly
cooled system. Lithium stearate and eetane sire inert toward
each other at temperatures below 170°, although lithium
stearate undergoes a transition from one solid form to
another at 115°.
If extensive recrystallization through Ostwald ripen
ing were occurring at a high temperature, it might be ex
pected that the system held at 155° for an hour would be
less capable of retaining liquid if particle growth and
perfection of crystals is the result. However, the opposite
is the result; the quenched system which was held at 155°
for one hour lost less liquid under pressure than the system
which was slowly cooled continuously.
Pressure s t a b i l i t y o f commercial g reases. As w ith
many commercial systems, the number o f p o s sib le v a ria b le s
179
affecting the results was too great to allow much in the way,
of an Interpretation to be made.
The experiments, however, served to indicate the
behavior of commercial greases toward the pressure stability
method. Considerable portions of the oil in every system
could be expressed by external pressures which are hardly to
be considered drastic.
The connection between the pressure stability results
and the filter paper test is indicated by Figure 31>. in
which 1/a, the Initial rate of loss, Is plotted against the
2
time at which equaled 1000 mm. from the filter paper
tests. The correlation is understandable If it is supposed
that both processes depend on the rate of flow of the oil
from the grease system. The connection between the initial
rate of loss and amount of syneresis over a six-month period
Indicated by Farrington and Humphreys (11 ) suggests that the
filter paper test gives an indication of the syneretic tend
ency of a grease.
The deviation of the rate expression of the present
results from that found with the capillary flow of liquids
Into papers has already been mentioned. Possible reasons
for this difference may be of Interest.
The first consideration is the geometry of the flow,
which is radial In the filter paper test. The assumptions
to be made for the following derivation are: (l) liquid
180
1000
FIGURE 31
COMPARISON OF PRESSURE STABILITY
AND FILTER PAPER TEST RESULTS
1/a vs. t at £±h = 1000
Q CAL.RES. na-i
A CA"I
SHE LL-LI MULTI-PURPOSE
I/A
C AL.RES.AL-2
.05
.15
l 8 l
spreads out radially from source, (2) rate of flow into
absorbing body is rate-controlling step, (3) Poiseuilie flow
into capillaries is followed, (4) number of capillaries is
proportional to the area, and (5) length of flow path is
proportional to the square root of the area.
Let:
n = number of capillaries per unit area of absorbing
body
1 = length of capillaries
i
Y = total volume of liquid in porous body covering area,
r = average radius of capillaries, a constant
Bj
V =tfnr2l
dV =TTr2 (ndl + ldn)
n « KqA
1 = K2A1/2
/
Combining the above equations gives an equation of the form
A = Kt if A a * O at t a s o
o r A = Kt if A = A at t = 0
This relation, when plotted logarithmically, gives a slope
of 1, rather than 0.66 as found with the filter paper test
results. However, if the more general assumptions are made
that
, dV ttP nr
it 84 1
1 = K2Ab
it can be shown that
Af.2b- A Sb = Kt
f o
If b = 1, the result is of the form
K A A + (A a)2 = Kt
A logarithmic plot of A A against t may give a straight line
I
'of slope between 1 and 2. If b = 0.33, the logarithmic plob
» * i
jwill resemble the present results. Without a knowledge of j
t
;b, the effect of geometry on the results cannot be deter
mined with certainty.
l . • • .
f Another way of accounting for the results is to
iassume that flow rate depends upon the flow from the grease
I
! rather than flow into the paper. Use of a narrow strip of
filter paper instead of the circular piece might be useful
to study such a factor.
It is possible to explain the t/s versus t plots for
the commercial grease systems in terms of the effect of the I
j
high viscosity of the oil on the rate of flow. Since the 1
sample rests in a porous thimble, it is possible that two
jregimes may exist. The first regime of flow will be that j
i i
jin which the flow rate is controlled by flow through the j
|thimble, while the second will be that in which the rate of
.
flow from the grease determines the over-all flow rate.
: -- rar
The flow of liquid through the porous thimble will
j follow Darcy’s Law (22) which for the present can be
I
]written as
dV = K dp
dt * ] dl |
i
where K is a constant which depends on the nature of the
porous medium among other things, t versus s will be a
straight line if the above relation is followed. The equa- I
;tion was tested in the case of the commercial systems by
i !
:plotting t against s. The results are shown in Figure 31.
i
Obviously the curve is linear in a certain time interval,
:tailing off as the time of application of pressure in
creases. It seems natural to ascribe the linear behavior to
the flow through the thimble as the rate-controlling process;
The slopes of the lines are not exactly in the order !
|predicted by the viscosities. The time at which the curves
I
!start to deviate from a straight line, however, are in the i
I
order of the viscosities of the oils. This is the expected
order since the time at which rate of flow from the grease
becomes the rate-controlling process will be lower, the
{
jlower the viscosity of the liquid. Systems containing
I
[liquids of relatively low viscosity, such as cetane, will I
1 *
not display such behavior to any extent, which is borne out i
■ I
by experiment. [
i
I Despite the obviously slower rates of expression of j
T (MIN)
FIGURE 32
FOR COMMERCIAL GREASES
3 CAM
20
30
hO
184
800
400
oil from commercial greases compared with loss rates from
cetane-containing systems, values of 1/a for the two types
of systems are fairly close. A simple explanation can be
given by Figure 31.
The values of a and b for commercial greases are
^determined only after a long time of running when the rate
t
of loss is very low. At comparable times, the curve for
cetane-containing systems will resemble that of the greases.
Extrapolation of the t versus s curve back to lower times
calculated from the t/s-t data may easily give similar
curves, regardless of the actual behavior of the grease, to
those of the cetane systems.
With respect to the structure of the grease itself
the results do not appear to be particularly valuable. The
liquid loss from the greases is generally higher than that
from cetane-containing systems. Without further evidence,
the effects of working the commercial systems cannot be held
responsible for the difference in pressure stability. The
possible difference in pressure stability caused by slow
collapse of the solid structure as opposed to a rapid col
lapse of the solid structure must also be considered.
General considerations of pressure stability results.
The results of the pressure stability experiments are not in
disagreement with a picture of grease structure in which
CALCULATED FROM
EMPIRICAL EQUATION
ACTUAL
BEHAVIOR
T
FIGURE 33
POSSIBLE PRESSURE STABILITY BEHAVIOR
OF COMMERCIAL GREASES
187
liquid is immobilized in capillary spaces caused by a matrix
of fibrous particles. The existence of relatively strong
interparticle contacts is not precluded as a possible
necessity for the existence of non-syneretic greases.
The present set of pressure stability data cannot be
fully utilized until representative particle sizes and shapes
are determined directly, probably by a microscopic tech
nique. A comparison of the two types of results will prove
useful in assigning the relative importance of the size and ,
shape of solid particles as a factor in preventing liquid
t
loss. Any marked connection in the direction indicated by
the geometrical considerations discussed would suggest size
and shape as primary factors.
B I B L I O G R A P H Y
BIBLIOGRAPHY
1. Adkins, Chapter 13 in Gilman, Organic Chemistry, John
Wiley and Sons, New York, 1943*
2. Bikerman, Surface Chemistry, Academic Press Inc., New
York, 19TfT
3. Birdsall and Farrington, J. Phys. Coll. Chem. 52, 1415
(1948).
4. Boner, Chapter in Colloid Chemistry, edited by
Alexander, Vol. VI, p. 553, Reinhold Publ. Co., New
York, 1946.
5* Burton and Kohl, The Electron Microscope, 2nd edition,
Reinhold Publ. Co., New York, 194b.
6. Deansley and Carleton, J. Phys. Coll. Chem. 45, 1104
(1941).
7. Doscher, Ph.D. Thesis, Univ. of So. Calif. Library,
December, 1946.
8. Doscher and Void, J. Phys. Coll. Chem. 52, 97 (1948).
9. Ellis, Can. J. Res. A25, 119 (1947).
10. Farrington and Davis, Ind. Eng. Chem. 28, 4l4 (1936).
11. Farrington and Humphreys, Ind. Eng. Chem. 31, 230
(1939).
12. Gallay and Puddington, Can. J. Res. 22B, 155 (1944).
13._________ , Can. J. Res. 24b , 73 (1946).
14. Grandine, 290L Report, Spring 1948, Univ. of So. Calif.
Library.
15- Hattiangdi, 290L Report, Spring 1948, Univ. of So.
Calif. Library.
16. Herschel, Proe. A.S.T.M. 33, Part I, 343 (1935).
17. Hoppler, Fette u. Seifen, 4£, 700 (1942).
190
18. Klemgard, Lubricating Greases, Reinhold Publ. Co., New
York, 1937-
19* Kolthoff and Shapiro, J. Phys. Coll. Chem. 52, 1020
(1948).
20. Lawrence, Trans. Farad. Soc. 34, 660 (1938).
21. McBain and McClatchie, J. Phys. Coll. Chem. 36, 2567
(1932).
22. Muskat, Flow of Homogeneous Fluids through Porous
Media, McGraw-Hill Book Co., New York, 1937*
23. Smith, 290L Report, Fall 1948, Univ. of So. Calif.
Library.
24. Sproule and Pattenden, Can. J. Res. F26, 465 (1948).
25. Void, M. J., N60NR-238-T0-2, Spec. Internal Rept #2,
August, 1948.
26. ________, submitted for publication.
27. Void, R. D., 1st Annual Report, Phase Studies of
Greases, N60NR-238T0-2, February, 1948.
28. , 2nd Annual Report, Phase Studies of Greases,
N60NR-238T0-2, February, 1949.
29. Void, Grandine, and Void, J. Coll. Sci. 3, 339 (1948).
30. Void and Void, J. Phys. Coll. Chem. ^2, 1424 (1948).
31. Void, Hattiangdi, and Void, submitted for publication.
32. Zachariasen, Phys. Rev. 53, 917 (1938).
U niversity o f S o u th e rn C alifo rn ia Ltbn v i

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Asset Metadata

Creator Coswell, Richard James (author)

Core Title A study of the pressure stability of calcium stearate-cetane systems containing additives

Degree Master of Science

Degree Program Chemistry

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag chemistry, inorganic,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Vold, Robert (committee chair), [illegible] (committee member), Copeland, C.S. (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c17-792348

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Rights Coswell, Richard James

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Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

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