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Investigation into the natural color photography (!) of crystalline precipitates

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Investigation into the natural color photography (!) of crystalline precipitates

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Content A N INVESTIGATION INTO THE N A TU R A L C O LO R PH O TO
G RA PH Y OF CRYSTALLINE PRECIPITATES
$
A Thesis
Presented to
the Faculty of the Department of Chemistry
Uhiversity of Southern C alifornia
In p a r ti a l fu lfillm e n t
of the requirem ents fo r the degree
Master of Science
by
Henry Clarke
Edna Schwerin
June, 1937
UM I Number: EP41485
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under the direction of 1& _air Faculty Committee,
and approved by all its members, has been
presented to and accepted by the Council on
Graduate Study and Research in partial fulfill
ment of the requirements for the degree of
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l _................
Dean
Secretary
D ate ^ A fA * ~. A f A Z.....
Faculty Committee
Chairman
PLATE I
A Chromatone P r in t of th e Agfa c o lo r
sc re en . The p r in t made by superim posing
tra n s p a re n c ie s s im ila r to th e bromide
p r i n t s on th e th r e e fo llo w in g pages.
r
M tiJ
PLATE I I
A Bromide p r in t made from th e blue
n eg a tiv e and toned yellow .
i i i
PLATE I I I
A Bromide p r in t made from th e green
n e g a tiv e and toned re d .
iv
PLATE IT
A Bromide p r in t made from th e red
n e g a tiv e and toned b lu e .
PLATE Y
A Chromatone P rin t o f Antimony-
Cesium c h lo rid e c r y s ta ls in a so lu
tio n of Potassium Io d id e,
v i
TABLE OF CO N TEN TS
Chapter page
I. INTRODUCTION 1
I I , G EN ERA L PROCEDURE . 7
I I I . DISCUSSION O F W O R K 11
I. Selection of color processes, 11
I I , The Agfa color p la te s in use. 12
Lighting. 12
Exposure. 13
C rystals photographed , 16
I I I . The Chromatone process 18
Lighting and f i l t e r s 18
Exposure. .. 18
Developing and toning of p o sitiv e s 19
IT. S U M M A R Y A N D CONCLUSIONS . 20
BIBLIOGRAPHY. 26
v i i
LIST QF PISTES
Finite page
I . A Chromatone P rin t of the Agfa color screen.
The p rin t made by superimposing transparencies
sim ilar to the bromide p rin ts in P lates II-IV ♦ .
I I . A Bromide p rin t made from the blue negative
and toned yellow . i i
I I I . A Bromide p rin t made from the green negative
and toned re d .. i i i
IV. A Bromide p rin t made from the red negative and
toned blue. lv
V. A Chromatone p rin t of Ant imony-Cesium chloride
c ry sta ls in a solution of Potassium Iodide.
CHAPTER I
INTRODUCTION
The increasing importance of recording the re s u lts of
s c ie n tific work by means of color photography emphasizes the
need fo r having color processes a t the disposal of every
s c ie n tific worker. The h isto ry of color photography goes
baok to the beginning of the nineteenth century. Such men
as Seebeck, Beoquerel, Herschel, Draper, and Hunt have des
cribed sim ilar processes whereby s ilv e r chloride might be
made responsive to the reproduction of c o lo r.1 These exper
iments are of in te re s t only in th a t they show the p o s s ib ility
of obtaining a su itab le process. The use of dyes which were
lig h t sen sitiv e was la t e r introduced. This embodied the
p rin cip le of the Grothus-Draper Law. Three an ilin e dyes which
bleached re ad ily were chosen to form the three fundamental
colors, th a t i s —red, green, and blue. (Maxwell* in 1860,
stated th a t a l l colors may be produced by the mixture of the
three fundamental o o lo rsj. When these dyes were coated on a
piece of paper and exposed to lig h t, each dye was decomposed
by the color complementary to th at dye. In red lig h t the
blue and green dyes w ill bleach out. In blue lig h t the
— 1-------------------
N eblette, C. B., Photography, I ts P rin cip les and
P ractice, D. Van Nostrand Co., IncNew York (193b), p 537.
z
green and red dyes w ill bleach out. In lik e manner the
green w ill remain and red and blue w ill decompose in green
lig h t. This method was advanced by such men as Cros, T ailor,
Worel, and Smith*
From th is early experimentation a valuable background
was la id fo r the recent developments in th is work* The a l l -
important p rin cip le th a t a l l color perception is the re su lt
of the three fundamental color sensations has led to the
development of the additive and the su b tractiv e processes*
The Autcchrome (now e x tin c t), KTodaeolor, Finlay, and Agfa
Color are examples of the additive process. The Chromatone,
Kodachrome, and Wash-Off R elief are examples of the su b tract
ive process. In th is study the Agfa Color p late and the
Chromatone Process were used. A b rie f description of each
method and th e ir p a rtic u la r ad a p ta b ility to the in v estig atio n
of c ry sta llin e p re c ip ita te s w ill enable one to in te rp re t
b e tte r the r e s u lts and conclusions.
The Agfa Color p la te s are manufactured by the Agfa
Company of Binghamton, New York. The problems involved in
securing an accurate reproduction of s c ie n tific work neces
s ita te s a knowledge of the construction of the p la te . A
g lass base is used to support a m ulti-colo r screen. This
screen i s composed of uniform grains of gum arabic which are
dyed red, green, and blue. They are incorporated in equal
amounts so no one color w ill predominate. Over th is special
3
screen Is spread a panchromatic emulsion. The p lates are
very slow, having a value of 0*5 Weston scale or S. 6 Ameri
can Scheiner. When the p late is exposed i t i s reversed, so
th a t the lig h t passes through the glass support, the mosaic
f i l t e r , and then the emulsion. The development of the p late
is carried on in a special developer. However, the process
is much the same as in ordinary work. Instead of fix in g the
p la te in a hypo bath, i t must now be reversed as the negative
image is in complementary colors—► that i s , the exact reverse
of what was photographed. To accomplish th is re v ersal, the
s ilv e r image must be removed and then allowed to develop
in white lig h t, so th at the remaining s ilv e r forms a p o sitiv e
image. The pro jection of these p la te s (as lan tern slid es)
presents a problem since they transm it only 14 per cent of
the incident lig h t. For fu rth e r inform ation on these p la te s
the reader i s referred to e ith e r the handbook supplied by
the manufacturer2 or the books on color photography,*5
The Chromatone Process, employing the p rin c ip le s of
the su b tractiv e process,4 rep resents one of the major devel
opments av ailab le to s c ie n tific workers. This process is a
2Agfa Color P lates, Agfa Ansco Corporation, Bingham
ton, New York. S6 pp.
^The Photography of Colored Objects, Eastman Kodak
Company, MocHester, New York, (1928), p 74*
4Ib id ,, p 80.
product of the Defender Photo Supply Company, Inc*, of
Rochester, New York* Since th is is a subtractive color
process, i t oan be used to make p rin ts in color* In th is
process three negatives taken with the proper red, green,
and blue f i l t e r s are necessary* These three negatives are
used to make three prints* The p rin ts are made on a special
type of bromide paper in which the emulsion is supported on
a th in (about one thousandth of an inch thick) collodion
film* The three p o sitiv es are then toned the complementary
color of the f i l t e r through which they were taken* That is
to say, the p o sitiv e made from the negative eaqposed through
the red f i l t e r is toned blue-green, the one from the green
f i l t e r is toned magenta, and the one from the blue f i l t e r is
toned yellow. These th ree toned transparencies are then
superimposed in re g is te r on a sheet of white paper. This
achieves a p rin t in n atu ral color. To th is process one
change was made. Instead of p rin tin g the p o sitiv e to be
toned yellow as a transparency, i t was printed on white
bromide paper* Then, the image on the bromide paper was
toned and the other two transparencies were superimposed on
the bromide p rin t. This method proved to be ea sie r to use
than the o rig in al. For fu rth e r information the reader is
referred to e ith e r the more recent books on color photography
or to the c irc u la r of information supplied by the manufacturer.
^Chromatone Process. Defender Photo Supply Co., In c.,
Rochester, New York*
5
These two processes deeribed above were selected
because of th e ir domination in the two respective f ie ld s of
the additive and the subtractive processes. The cost and the
ease of manipulation were prime fa c to rs involved in the selec
tio n . Secondary fa c to rs were namely* available equipment
and type of s c ie n tific work under process.
The purposes of the study were to obtain a permanent
record of the c ry sta llin e p re c ip ita te s of cations in color,
using the two processes mentioned. These p la te s and records
may be used in demonstrations or as a means of revealing
c ry sta llin e stru c tu re th at is not d istinguishable with the
ordinary black and white p rin t or with the naked eye. This
study is n ecessarily lim ited in i t s scope of the s c ie n tific
fie ld , but i t is hoped th a t the system of color photography
used may be at the disposal of every s c ie n tific worker.
The need fo r such a development is clea rly recognized
by chemists, biochem ists, crim inologists, and other inves
tig a to r s . D etail and contrast are lo s t in many oases with
the common black and white p rin t, thereby losing the p o ssi
b i l i t y of obtaining an accurate reproduction which is neces
sary i f the p rin t is to reveal new stru c tu re s. Contrast
w ithin the cry sta l or the object is of utmost importance.
The color p rin t and the color p la te have been used to
obtain photomicrographs which would permit the in v estig ato r
to fu rth e r his work of research and an aly sis beyond th at
a ttain ed with the ordinary p r in t.
6
Some of the problems th a t were involved and in v e s ti
gated in the study were: 1. proper lig h tin g , 2. exposure,
3. depth of foous, 4. m agnification, and 5* choice of field*
Exposure and proper lig h tin g were problems of a more serious
nature and therefore w ill receive more consideration* Prob
lems such as m agnification were standardized to aid in sim
p lify in g the actual procedure involved* D etails of the
apparatus and the prooesses w ill be developed in th e ir pro
per sequenoe* Other problems a risin g a f te r the selec tio n of
the c ry sta l to be studied w ill be discussed under th a t
section devoted to the c r i t i c a l analysis of the photography
of such crystals*
CHAPTER I I
G EN ERA L PROCEDURE
The apparatus necessary fo r th is work consisted of a
good standard lig h t source, a miorosaope, and a v e rtic a l
camera, A complete set of reagents fo r microchemical anal
y sis , a good set of s lid e s , and the photographio m aterials
complete the equipment. An explanation of the lig h t source
is of fundamental importance. An ad justable microscope
lamp was used. This equipment perm itted the use of f i l t e r s
in fro n t of the lig h t source. The standard illum inant was a
Photoflood lamp fo r both the Agfa Color p la te s and the
Chromatone process. The Photoflood was used to cut down the
exposure time. This source was also selected as i t perm itted
the use of the p la te s without additional f i l t e r s . However,
the Agfa p la te s have, during the course of the research,
been changed, so th at a compensating f i l t e r is now required.
The microscope used contained a substage condenser.
The purpose of th is condenser i s to image the lig h t on the
c ry sta ls to be viewed. To obtain the best reso lu tio n of
d e ta il the cone of lig h t should f i l l the back lens of the
objective. To accomplish the ET-A . of the condenser must be
equal to or g reater than the N.A. of the o b jectiv e.
In some cases an objective was used th a t contained a
8
diaphragm* This permitted one to secure b e tte r d e ta il and
g reater depth of focus. The power of the objective was held
to a minimum to secure g reater depth of focus. The magnifi
cation was increased by extending the bellows on the v e rtic a l
camera*
An accurate record of each photograph was kept to
enable a c r it i c a l survey of the work. The exposure time,
type of objective, condenser, diaphragm opening, lig h t source,
reagents used, and development were recorded fo r eaoh photo
micrograph.
C rystals were prepared using such data as was supplied
i
by Chamot and Mason and other outstanding a u th o ritie s on
the subject. The fa c to rs a ffe c tin g cry sta l growth, such as
concentration of the reagents, s tir r in g , and seeding were
controlled so as to fo s te r large c h a ra c te ris tic c ry s ta ls .
The time elapsing between the preparation of the slid e and
the exposure of the p late was kept at a minimum. In same
cases c ry sta ls were affected by evaporation, while in o th ers,
notably copper, the c ry sta l became covered with an amorphous
p recip itate*
In some cases the c ry sta ls were of such a nature th a t
2
a dark f ie ld was used in place of the transm itted lig h t.
----------------
•^Chamot, S. M., and Mason, C. W., Handbook of Chemical
Microscopy, John Wiley and Sons, New York, (1931), Yol I I , pp 599.
2Ib id .. p 87.
9
In bright f ie ld illum ination, the c ry sta l must absorb or
re fra c t the lig h t passing through it* In th is way contrast
is set up between the c ry sta l and the medium* However, with
the use of the dark f ie ld , the d ire c t lig h t does not enter
the microscope* The oblique rays from the edges of the
condenser w ill en ter the c ry sta l, which w ill in turn bend the
rays so th at some w ill en ter the microscope. The use of the
dark f ie ld n e c e ssita te s th a t the N.A. of the condenser be
g reater than th a t of the objective. The special advantage th at
dark f ie ld illum ination possesses Is th a t one secures a g reater
degree of c o n tra st. In some cases the color of the c ry sta l
would not be apparent when viewed in the bright fie ld , but
with the dark fie ld the c ry sta ls showed th e ir colors.
C h aracteristic featu res of c ry sta ls revealed with
polarized lig h t were recorded. Here, a dark f ie ld resu lted
giving the advantage described above* The same apparatus
was used to standardize the exposure required.
Exposure is of fundamental importance in making any
type of photograph. In th is work the Agfa P late i s lim ited
in i t s la titu d e although i t s range is su rp risin g . To obtain
the exposure one te s t s trip was made. This was done in the
usual manner. The p late was exposed progressively so th a t a
range of exposures was obtained on one p la te . From th is
^Dark Field Optical Systems* Bausch and Lomb Optical
Co., Rochester, Hew York, (1934), 16pp.
xo
selectio n one exposure was chosen representing the desired
brightness of color (in an Agfa p la te i, co n trast, d e ta il,
and proper density.
The development of the p la te s in the Chromatone
Process follows that of any panchromatic p la te , using a
suitable developer. However, in the case of the Agfa P lates
a special developer was necessary. This was prepared accord
ing to the formula supplied by the manufacturer. The re
versing bath was also prepared as direoted, but in th i s case
i t was observed th at the stook solution d e te rio ra te s a f te r
standing fo r seme time. Proper care th a t fresh developer
and reversing bath were used was of utmost importance. If
th is precaution is not observed, the p late may not be develop
ed or reversed fu lly , giving a f l a t p ictu re.
In the making of a Chromatone p rin t special toners
were needed which were supplied by the company. This process
requires th at the p rin ts be of quite accurate density.
Special te s t s trip s were made to compare the three p rin ts
so th a t the d en sities would be in accord with the amount of
color present in the c ry sta l o rig in a lly .
CHAPTER I I I
DISCUSSION OF W O R K
In th is chapter the work w ill be discussed and
described in d e ta il. S p ecifically , i t w ill include the
following d iv isio n s: 1. Selection of color processes. 2.
Discussion of the problems encountered in using the Agfa
color process. 3. Discussion of problems encountered in
using the Chromatone prooess.
I . SELECTION OF C O LO R PROCESSES
Since at the outset of the in v estig atio n i t was de
cided to te s t one example of both the subtractive and additive
methods, the f i r s t problem resolved i t s e l f into making a
choice among the various commercial processes av ailab le. As
mentioned before, of the additive there were the Agfa, Finlay,
and Kodacolor processes av ailab le, and of the subtractive
the Wash-Off R elief, Kodachrome, and Chromatone. In making
a choice as to the processes to be used there were ce rtain
determining fao to rs. These were as follow s: accuracy of
reproduction, ease of m anipulation, a d a p ta b ility to equip
ment av ailab le, cost of m aterials, and a number of secondary
fa c to rs such as emulsion speed, la titu d e of exposure, e tc .
I t was extremely desirable th at there be as few steps as
12
possible where e rro rs could be introduced in the processing
of the finished p rin t or p o sitiv e . The Agfa was esp ecially
su itab le in th is respect, and of the three subtractive pro
cesses the Chromatone was the most d esira b le . Likewise in
ease of manipulation the Agfa was superior to the other pro
cesses. Also, since the photographs were desired in the
form of lan tern slid e s, the glass support of the Agfa emul
sion as contrasted with the film support of the others was
an advantage. A fter a consideration of the above fa c to rs,
consulting experienced workers and references on the sub
ject,^* and the technical data supplied by the various manu
fa c tu re rs, the Agfa and Chromatone processes were selected
as the examples of the additive and subtractive methods best
suited to th is investigation*
I I . THE A G FA C O LO R PLATES IN USE
L ighting* The f i r s t problem encountered in using the
Agfa color p la te s was th a t of lig h tin g . The f i r s t lig h t used
was a 60 watt Mazda bulb in an adjustable microscope lamp,
th is being the la rg e st sized bulb the lamp would hold. This
lig h t source caused a number of more or le s s important d i f f i
c u ltie s . In the f i r s t place the in te n sity was such as to
require inordinately long exposures—from three to fiv e min
u te s. With exposures of th is length the solution s containing
^See bibliography
1 3
the c ry sta ls evaporated due to the heat of the lamp, causing
the c ry sta ls to move about the fie ld and the p re c ip ita tio n of
fresh c ry sta ls . This condition was remedied somewhat by the
use of a cooler between the microscope and the lamp. The
cooler, however, cut down the lig h t in te n sity s t i l l fu rth e r,
thereby n ecessitatin g s t i l l longer exposures, so th at the
arrangement was not alto g eth er s a tisfa c to ry . A second
d iffic u lty with such a low in te n sity lig h t was th a t the image
on the ground-glass focusing screen was so fa in t th a t c r itic a l
focusing was very d i f f i c u l t . And th ird ly , from some of the
p lates taken there was reason to believe th a t the q u ality of
the lig h t was in c o rre c t.
The f i r s t lig h t to be considered as a su b stitu te was
an arc lig h t. However, as the arc lig h t is subject to f a ir ly
large v a ria tio n s in both the in te n sity and q u ality (as d if f e r
ent carbons are used), i t was elim inated. A Photoflood bulb
was tr ie d next. This type of lig h t bulb using between
750 and 1000 w atts, is the same size as a standard 60 watt
bulb (so th at i t could be used in the microscope lamp), gives
an intense white lig h t, and has the ad ditional advantage th at
there is no f i l t e r required when using the Agfa p la te s .
With a bulb of th is type the average exposure was around
25 seconds, and the d if f ic u ltie s encountered with the weaker
lig h t source were larg e ly elim inated.
Eacposure. Due to the cost of the p la te s i t was ex-
1 4
tremely desirable th a t some method of standardizing exposure
be developed. The f i r s t method to be tr ie d was to use a
standard Weston Exposure Meter. The meter was tr ie d in two
d iffe re n t p o sitio n s, at the plane where the plate is exposed
and ju st above the eyepiece of the microscope. In n e ith e r
position was there su ffic ie n t d eflectio n of the galvanometer
to give any indication of the re la tiv e lig h t in te n sity ,
even though both the substage and objective diaphragms were
open to th e ir larg e st aperture. In the next instrument
trie d , a comparison was effected v isu a lly between two p araf
fin blocks, one illum inated by the unknown lig h t and the
other by a standard lig h t source. In use a calib rated rheo
sta t was conneeted in se rie s with the standard lig h t bulb
(a 6.3 volt fla s h lig h t), and the resistan ce varied u n til the
in te n sity in both blocks was apparently equal. Then a l l the
other fa c to rs being constant, the exposure w ill be d ire c tly
proportional to the value of the re sista n c e , and the
rheostat can be calib rated d ire c tly in seconds exposure.
After a number of t r i a l s th is apparatus had to be discarded
because the d iffic u lty in matching the lig h t in te n s itie s
allowed erro rs of su ffic ie n t magnitude to e ith e r over- or
under-expose the p la te s. With the fa ilu re of these methods,
re so rt was made to the process of making te s t exposures;
though due to the cost of the p la te s i t was not possible
to make te s t exposures of more than a few of the p la te s made,
1 5
requiring the m ajority to be exposed on the b asis of past ex
perience and a correct judgement of the c ry sta ls under con
sid era tio n . It was with exposure th a t the g reatest d i f f i c u l t
ie s were encountered in using the Agfa p la te s . It is the
opinion of the in v estig ato rs th a t th is shortness of la titu d e
represents the most serious shortcoming of the Agfa p la te s .
Another d iffic u lty encountered in connection with
exposure was th at under id e n tic a l conditions d iffe re n t colored
c ry sta ls required d iffe re n t exposures. For example, the
f i r s t c ry sta ls photographed were those of cobalt mercuric
thiooyanate (Co(S(ai)g#Hg(S(2Jlg)[, which are dark blue in
color. In the case of these c ry sta ls the correct exposure
was found to be about 25 seconds while under the same con
d itio n s c ry sta ls of s ilv e r bichromate (AggCrgO^j or gold
ions plus a solution of pyridine and hydrobromic acid
(composition unknown), both of which are red, require an
exposure of from 35 to 45 seconds. In general c ry sta ls which
are yellow or orange or red require a longer exposure than
those which are blue or v io le t.
Another case where exposure was found to vary was in
the use of dark fie ld illum ination. For example, when using
a patch to obtain a dark fie ld , the exposure fo r cobalt mer
curic thiocyanate was 32 seconds, while without the patch
( i . e . , with lig h t fie ld ) the exposure was 25 seconds. As
would be expected, between crossed n ico ls the exposure was
1 6
greatly increased. For example, when using th is means of
obtaining a dark f ie ld , the exposure fo r gold ions plus a
solution of pyridine and hydrobromic acid (gold pyridine
double bromide cry sta ls) was 70 seconds, while without the
nico ls the exposure was 40 seconds* The use of a dark fie ld
improves the projected appearance of the Agfa p lates by in
creasing th e ir c o n tra st.
C rystals photographed. In selectin g the cry sta l to
be photographed an attempt was made to include the most used
te s ts fo r each of the common metals where a colored p re c ip ita te
i s formed* In the tab le below is a p a r tia l l i s t of the photo
graphs taken with the Agfa p la te s, giving rep resen tativ e data
about each.
TABLE I
CRY STA L TEST FOR C O LO R EXPOSURE FIELD
Ag2Cr207 S ilver Red 38 sec. dark
AggCPgO? S ilver Red 25
tt
lig h t
Ammonium arseni
molybdate Arsenic Yellow 25
r
lig h t
Au, pyridine & HBr Gold Red 40
r
dark
BePtCl§*8HgQ Beryllium Yellow 25
r
lig h t
Co (SO N J g*Hg( SCN) g Cobalt Blue 25
r
lig h t
Co(SCH) g*Hg(SCN}g Cobalt Blue 32
r
dark
CsTeClg Tellurium Yellow 25
r
lig h t
CuCSCNjg-HgfSCNjg Copper Green 25 lig h t
Cu(Sd?)2*Hg(SCH)2 Copper Green 35
r
dark
1 7
TABLE I (continued)
CRY STA L TEST FOR C O LO R EXPOSURE FIELD
Hglg Mercury Orange 50 sec,. lig h t
K2PtCl6 Potassium Yellow 35 ^ lig h t
Pbl9 Lead Yellow 45 * dark
Ill* THE C H R O M A T O N E PROCESS
1 8
Lighting and f i l t e r s * With a single exception the
lig h t source used in making the negatives for a l l the Chrom-
atone p rin ts was a Photoflood in an adjustable microscope
lamp* This had the advantage of g re atly shortening the ex
posure time, which was very important in view of the fact
th a t there were three p la te s to be exposed, and any s lig h t
movement of the c ry sta ls would sp o il the e n tire p ic tu re .
Using a 60 watt bulb in the microscope lamp required exposures
of 10, 11, and 15 minutes fo r the red, green, and blue p la te s ,
while with the Photoflood bulb the corresponding exposures
were 22, 88, and 320 seconds* The three f i l t e r s used were
the Wratten #25, #58, #49b. The f i l t e r s have fa c to rs of
10, 11, and 15 resp ectiv ely (when used with a Photoflood
bulb} though these values vary somewhat according to
emulsion* In use the f i l t e r s were placed in the beam of
lig h t between the lamp and the re fle c tin g m irror of the
microscope*
Exposure* In the Chromatone process i t was very im
portant to have the negatives exposed co rrectly , since i t is
upon th is th at the accuracy of the color reproduction de
pends. However, the Eastman Process Pan p la te s which were
used in making the negatives have a f a ir ly wide la titu d e of
exposure, so th at l i t t l e trouble was encountered with th is
fa c to r. The procedure in making the negatives was to f i r s t
1 9
make a te s t exposure to obtain the correct exposure time,
and then to expose the three p la te s as rapidly as possible
through the proper f i l t e r s . If too long was taken in ex
posing the p la te s there was danger of the solution evapor
atin g and the c ry sta ls moving about or fresh c ry sta ls being
p re c ip ita te d . In general i t was found best to s lig h tly over
expose the negatives fo r the Chromatone prints*
Developing and Toning of P o s itiv e s* With the Chrom
atone process the major d if f ic u ltie s were encountered in the
making of the black and white p o sitiv e s. Obtaining the
correct n eu tral scales in each of the p o sitiv e s was an espec
ia lly d if f ic u lt and important poin t. Upon th is depends the
accuracy of the color reproduction (assuming the negatives
to be exposed c o rre c tly ). The three p o sitiv e s were printed
with an enlarger which perm itted more control over exposure
than would be possible with contact p rin tin g . The procedure
here was to make a se rie s of te s t p rin ts from each of the
negatives, and to compare them to find the correct exposure
in each case to give the p o sitiv e neutral scales th a t were
about equal. While th is method was both tedious and w asteful,
there appears to be no other way to approach the problem. In
the toning of the p rin ts there were no special d if f ic u ltie s
encountered.
CHAPTER IY
SU M M A H T A N D CONCLUSIONS
In th is work special a tte n tio n was given to the
color processes representing the additive and the su b tract
ive type. The fa cto rs determining the selectio n of the Agfa
Color p late and the Chromatone Process have been elaborated
in the previous chapter* These fa c to rs are of great import
ance in determining the type of color photography th a t can be
made available to the s c ie n tific in v estig ato r. Economy, ease
of manipulation, accuracy of reproduction obtained, and
equipment required are the necessary fa c to rs that determine
the selectio n .
The Agfa Color p late was used to make lan tern slid e s
of the c ry sta ls of the following cations: copper, cobalt,
s ilv e r, gold, lead, potassium, mercury (ic ), antimony,
strontium , manganese, vanadium, arsenic, zirconium, thallium ,
and beryllium . The construction and technique involved in
the use of the Agfa Color p late has been dicussed f u lly . The
set up used in th is work enabled one to standardize many of
the variable that determine the success or fa ilu re of the
p la te .
The equipment used remained the same throughout the re
search. This sim plified the problem of exposure and
2 1
lig h tin g . Exposure and proper lig h tin g are problems which
are of paramount importance in obtaining good b rillia n c e in
the colors and accurate cry sta l d e ta il. The problem of
lig h tin g was considered f i r s t . The 60 watt Mazda bulb was
u n satisfacto ry . The exposure was too lengthy and a pure
white lig h t could not be obtained. To overcome these d i f f i
c u ltie s , a Photoflood was su b stitu te d . This produced a s a t i s
factory white lig h t and reduced the time of the exposure.
With th is lig h t source, focusing was more e f f ic ie n t, giving
b e tte r d etail*
Exposure, n a tu ra lly , a ffe c ts the production of a good
p la te . To obtain the correct exposure for the various c ry st
a ls with or without a dark f ie ld , with or without polarized
lig h t, a Weston meter was f i r s t tr ie d . This apparatus was
found to be u n satisfacto ry . Then a method was devised to
compare the in te n s itie s of the lig h t at the position of
p la te with that of a standard lig h t source. These experi
ments have been fu lly re la te d previously, and have been found
to be inadequate in furnishing accurate information from
which the exposure may be calculated. With the lig h t source
standardized, and the adjustments of the microscope recorded
at each exposure, a set of exposure times could be obtained
that gave s a tisfa c to ry r e s u lts . Test p la te s were made in the
usual manner, and the exposure time calculated fo r that par
tic u la r type of p la te . With the use of polarized lig h t the
22
the exposure was three times th a t given for the p la te s
taken with transm itted lig h t giving a bright f ie ld . However,
when using dark fie ld illum ination the exposure was not in
creased to such a large degree. In most work to obtain a
p la te giving good b rillia n c e and a proper background 25
seconds was s u ffic ie n t. With the dark fie ld illum ination the
exposure was approximately 55 seconds.
In the above discussion polarized lig h t and dark
fie ld Illum ination was mentioned as a means of obtaining
p ic tu re s of c ry sta ls. In many cases the c ry sta ls lacked
d e ta il and appeared so weak in color that photography with
the use of the bright fie ld would re s u lt in a p la te that
had l i t t l e value. The dark fie ld and the use of polarized
lig h t give the s c ie n tific worker ample to o ls to obtain good
con trast and d e ta il. With the polarizin g microscope the
f ie ld of chemical in v estig atio n can be extended immensely.
P roperties otherwise hidden can be observed, and recorded in
co lo r, preserving the o rig in al p ic tu re .
Fiaintly yellow c ry sta ls presented a problem which in
most cases could be photographed more accurately with the
use of the dark f ie ld . The strontium c ry sta ls were photo
graphed with the use of the dark f ie ld , revealing b e tte r
d e ta il and a b r illia n t yellow. Copper c ry s ta ls , which are
long and narrow, were harder to photograph inasmuch as the
area of actual color was small. Much of the trouble was due
23
to overexposure* With b e tte r c ry sta l growth fo sterin g large,
wide c ry sta ls and shortening the time elapsing between crys
ta lliz a tio n and making the exposure, a good p la te of copper
c ry sta ls, using potassium mercuric thiocyanate, can be made*
If the plate is overexposed or underexposed, correction may in
some cases be b en e ficial by in te n s ific a tio n or reduction.
The Chromatone Process presents a desirable method fo r
use in s c ie n tific in v estig atio n s. Here, p rin ts may be made
in color. This is an advantage over the Agfa P la te , with
which only one p late could be made. In th is process one can
make as many p rin ts as desired from the o rig in al three neg
atives* A d etailed account of the process has been given
which suggests the length of time and d if f ic u ltie s encounter
ed in making a print* The negatives made with the three
proper f i l t e r s must of necessity have the proper density in
accord with the amount of color present in the crystal* This
seems to be basic in obtaining a tru e reproduction* From
th is point the process can be controlled quite easily* The
p rin tin g time in making the p rin t must not be too sh o rt. In
the work the tendency was to give too l i t t l e exposure with
the re su lt th at the color obtained and the background were not
strong* To safeguard against suoh fa ilu re s , exposures should
be made th a t give the p rin t a good black background. After
the p rin ts have been given the proper exposure in re la tio n
to each other, the p rin ts are ready to be toned. This pro-
24
pess has been described and fu rth e r elaboration Is unnecessary.
Gold pyridine hydrobromide was photographed under the p o lar
izing microscope as was s ilv e r dichromate. These two p rin ts
were an accurate reproduction of the c ry sta ls as viewed.
However, the background of the s ilv e r dichromate p rin t appears
to have a fa u lty black. With fu rth e r experimentation b e tte r
re s u lts could be obtained. The p rin t from the negative taken
through the blue f i l t e r should have a good black background,
i f the c ry sta ls photographed contain very l i t t l e blue.
Due to the cost of the toners and p rin tin g paper the
research in th is fie ld has been lim ited . With the e sta b lish
ment of toners th at can be compounded in the laboratory,
as other photographic formulas are, th is process seems id e a l.
The p o s s ib ility of having color photography available
to record a l l s c ie n tific in v estig atio n s, chemical or other
wise, seems to be p ra c tic a l and necessary. With increased
accuracy in most s c ie n tific instrum ents, a means of obtaining
a tru e , permanent record seems to be necessary. The two
processes used in th is research indicate th a t color photo
graphy can be made av ailab le. The expense of the Agfa Color
p late can be minimized by considering the value of such a
co llectio n fo r a permanent record, for demonstrational
purposes, and as an aid in c r it i c a l analysis of re s u lts .
Of the two methods the Chromatone Process seems to hold the
b e tte r fu tu re . With fu rth e r research suitable toners may be
25
developed which w ill elim inate the expense now connected
with the system. This also may re su lt in a set of toners
which w ill sim plify the procedure.
A complete record of a l l the p rin ts and p la te s i s on
f i l e at the o ffic e of the chemistry department. The record
of each p la te includes such information as exposure, mag
n ific a tio n , reagents, ob jectives used, development, and a l l
other v ita l ffaotors. The p la te s and records have been c a t
alogued so th at the record may be obtained e a sily fo r each
p la te .
BIBLIOGRAPHY
Babshaw, John 1 ., Elementary Phot o-miorography, I l i f f e and
Sons Limited, London (190&). 103pp7
Barnard, John I*, and Frank V. Welch, P rac tica l Photo-micro
graphy, 3rd ed itio n , Longmans, Green and C T o*, New York
Buxbaum,. Edwin C ., "Photography in the Chemical Laboratory” ,
Commercial Photography £,248-50 (1934)*
Chamot, Emile M., and Clyde W . Mason, Handbook of Chemical
Microscopy, John Wiley and Sons In c ., York (1931).
2 volumes--474 and 412 pp .
This is the standard and a u th o rita tiv e reference on
th is su b ject.
d e r o , Louis P h ilip p i, The Ilfo rd Manual of Process Work,
Ilfo rd Limited, London (1926)7 £81 pp.
Gives considerable m aterial on the various color
processes.
Conrad, A. E ., and others, Photography as a S c ie n tific
Implement, Van No strand and Co., New York (1983). 549 pp.
Coppin, F. W., "Three Color Separation Negatives", Photo
graphic Journal, 75.402-7 (1933).
Bark Field Optical Systems. Bausch and Lomb Optical Co.,
Rochester, New Y o rk (l9 3 4 ). Id pp.
Dunn, Carlton E ., Natural Color Processes, American Photo
graphic Publishing Co77 fT9'36"J • 194 pp.
Fanstone, Robert M., Color Photography, 2nd ed itio n , Pitman
and Co., London t1935)7 171 pp.
Hind, H. Lloyd and W . Brough Randles, Handbook of Photo-
~ .d ed itio n , Rout ledge Limit edT* London
Johnson, George L ., Photography in Colors. Routledge Limited,
London (1922). 318 pp.
One of the best books on the subject
2 7
Mees, Charles E. K ., The Photography of Colored Objeots»
Wratten and Wainwright, Croydon TT9Q9). 69 pp.
l^ees, Charles E. K., Photography. Macmillan and Co.. New
York (1937).
N eblette, C. B ., Photography. I t s P rin cip les and P ra c tic e .
D. Van No strand and Co., Sew York (1930) * 615 pp.
One of the best books on the general fie ld of photo
graphy.
Newens, Frank R., The Technique of Color Photography. Blackie
and Sons Limited, London (1 ^ 6 ) . 161 pp.
The Photography of Colored Objects, 13 ed itio n , Eastman
Kodak Co., lo c h e ste r, Sew York (1935). 68 pp.
Photomiorography, 11th ed itio n , Eastman Kodak Co., Rochester
New York, (1931J. 68 pp.
Shelton, A. C., Color Photography Direct with Agfa Color
P la te , Arnerican Dyestuff Reptr., 25, S14-1S (1 9 3 6 ).
Spencer, D. A., "Progress in Color Photography", Journal
and Technical Supp., 72,21-3 (1932).
Wall, E. J . , The History of Three-Color Photography. Amer
ican Photographic PuFTishing Co., Boston (1S2S)•

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Creator Clarke, H. C (author)

Core Title Investigation into the natural color photography (!) of crystalline precipitates

Degree Master of Science

Degree Program Chemistry

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

Tag chemistry, analytical,OAI-PMH Harvest

Language English

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Permanent Link (DOI) https://doi.org/10.25549/usctheses-c17-787113

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Rights Clarke, H. C.

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Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

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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