The determination of free alkali or free fatty acids in soaps

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Content THE DETERMINATION OF FREE ALKALI
OR FREE FATTY ACIDS IN SOAPS
A T h e s is
P r e s e n t e d to
t h e D e p a rtm e n t o f C h e m is try
U n i v e r s i t y o f S o u th e r n C a l i f o r n i a
I n P a r t i a l F u l f i l l m e n t
o f t h e R e q u ire m e n ts f o r t h e D e g re e
M a s te r o f S c ie n c e
By
W erner 0. S c h u b e r t
l u n e , 1939
UMI Number: EP41519
All rights reserved
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UMI EP41519
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This thesis, written by
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presented to and accepted by the Council on
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M a s te r o f S c ie n c e
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Date... -J u ly 19-3©
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TABLE OF CONTENTS
PAGE
I . IMPORTANCE OF A RELIABLE ANALYSIS . . . . . . . . . . 1
D a n g er o f R a n c i d i t y o f t h e Soap . . . . . . . . I
W hite S u r f a c e C o a tin g o f t h e Soap . . ..................... 1
The M ethods in U se a r e U n s a t i s f a c t o r y ..................... 2
I I . INVESTIGATION OF THE DIFFERENT M ETH O D S...................... 3
E x a m in a tio n o f t h e M ethods "by t h e S u b -C o m m ittee
o f P u b l i c - A n a l y s t s an d o t h e r A n a l y t i c a l Chem
i s t s ............................................................................................................. 4
S u g g e s tio n s o f t h e M ethods by t h e S u b -C o m m ittee 5
I I I . DIFFICULTIES IN DETERMINING FREE ALKALI AND FREE
FATTY A C I D S ........................................................ 7
I n c o m p le te S a p o n i f i c a t i o n .................................................... 7
S o a p - b u i l d e r s .................................................................................. 7
C arbo n D io x id e A b s o r p tio n .................................................... 7
H y d r o l y s i s ............................................................................ 7
IV. PURPOSE OF INVESTIGATION AND ORGANIZATION OF W ORK 8
S e l e c t i o n o f R e fe r e n c e Sam ple .......................................... 8
C o m p lete S a p o n i f i c a t i o n b y R e f lu x C o n d e n sin g . . 9
P r e p a r a t i o n o f S a m p l e .................................................................... 11
A n a ly s e s o f S a m p l e s ..........................................................................11
I n t e r p r e t a t i o n o f R e s u l t s .................................................... 14
New M e t h o d .................................................................................................14
V. SUMMARY...............................................................................................................16
V I. ' BIBLIO G RA PH Y ..............................................................................................18
LIST OF TABLES
TABLE PAGE
I . S a p o n i f i c a t i o n V a lu e s o f Some F a t s and O i l s A f t e r
D i f f e r e n t P e r i o d s o f B o i l i n g ................................................ 10
I I . C om p arison o f R e s u l t s O b ta in e d b y F i l t e r i n g an d
C e n t r i f u g i n g ........................................................................................ 13
THE DETERMINATION OF FREE ALKALI OR
FREE FATTY ACIDS IN SOAPS
One i m p o r t a n t q u e s t i o n i n t h e so a p i n d u s t r y i s t h e
p ro b le m o f t h e d e t e r m i n a t i o n o f t h e f r e e a l k a l i o r f r e e
f a t t y a c i d s i n s o a p s . C h e m is ts h a v e i n v e s t i g a t e d an d w r i t t e n
much a b o u t t h e m eth o d s em p loy ed, b u t none o f t h e a n a l y t i c a l
p r o c e d u r e s p r o p o s e d h a s g iv e n s a t i s f a c t o r y r e s u l t s . I t i s
v e r y i m p o r t a n t t o know t h e a c c u r a t e am ount o f f r e e a l k a l i ,
e s p e c i a l l y i n t h e c a s e o f h a r d s o a p s , s i n c e t h e r e i s d a n g e r
o f s p l i t t i n g a s m a ll p a r t o f t h e so a p i n t o f r e e f a t t y a c i d s
and f r e e a l k a l i , w h ic h g r a d u a l l y c h a n g e s i n t o a l k a l i c a r b o n
a t e . The f r e e f a t t y a c i d s so l i b e r a t e d l e a d t o r a n c i d i t y .
F o r t h i s r e a s o n t h e so ap m u st b e s a p o n i f i e d c o m p le te ly an d
f i t t e d w i t h 0. 1$ t o 0. 2$ f r e e a l k a l i b e f o r e i t l e a v e s t h e
k e t t l e . A c c o rd in g t o Knigge^- 0 .1 $ f r e e a l k a l i i s fo u n d t o
b e t h e m o st f a v o r a b l e am ount, w h ic h d o e s n o t p r o v e t o b e u n
p l e a s a n t f o r t h e co n su m er. The p e r c e n t a g e o f sodium h y d ro x
i d e l i b e r a t e d b y h y d r o l y s i s i s c o n s i d e r a b l y l a r g e r (a few
t e n t h s o f 1$ ) t h a n t h e f r e e a l k a l i . .
K h ig g e recom m ends 0. 1$ b e c a u s e th e b a s i c so a p s u f f e r s
a d e f i n i t e l o s s i n f r e e a l k a l i when b e in g p r o c e s s e d t o t h e
f i n i s h e d c a k e ( m o s tly d u r i n g d r y i n g ) . In some c a s e s t h e
f r e e so d iu m h y d r o x id e c o n t e n t w as d im in is h e d a lm o s t t o
n o t h i n g . B u t i f to o much f r e e a l k a l i was a d d ed , on t h e
K n ig g e , " D e te r m in a tio n o f F r e e A l k a l i i n S o a p s ,”
A m erican P e r f u m e r . 2 9 :4 0 3 - 4 , O c to b e r, 1934.
3
o t h e r h a n d , t h e so a p becam e c o a t e d w i t h w h ite sodium c a r b o n
a t e on t h e s u r f a c e . The e x c e s s so d iu m h y d r o x id e had c h an g ed
i n t o so diu m c a r b o n a t e .
S in c e t h e m a j o r i t y o f so a p s a r e d r i e d i n o p e n co n
v e y o r s , t h e c h e m ic a l t r a n s f o r m a t i o n s o c c u r r i n g t h e r e b y m u st
b e c o n s i d e r e d when d e te r m i n i n g t h e f r e e a l k a l i c o n te n t b e f o r e
and a f t e r d r y i n g . The so a p m a n u f a c tu r e r m u st b e i n a p o s i
t i o n t o d e te r m in e e x a c t l y t h e f r e e a l k a l i c o n t e n t . B u t t h i s
was n o t p o s s i b l e b y t h e m eth o d s u s e d so f a r . I n some c a s e s
s o a p s c o n t a i n i n g f r e e a l k a l i w e re r e p o r t e d t o h a v e f r e e
f a t t y a c i d s .
A few o f t h e m o st g e n e r a l l y em p lo y ed m e th o d s o f a n a ly
s i s a r e o u t l i n e d a s f o l l o w s :
A c c o rd in g t o t h e m ethod o f t h e German Soap M anufac
t u r e r s o f Germany t h e f o l l o w i n g p r o c e d u r e i s u s e d : 10 gm.
o f so ap a r e d i s s o l v e d on t h e w a t e r b a t h i n 100 gm. a b s o l u t e
a l c o h o l and s e p a r a t e d b y f i l t e r i n g t h r o u g h a h o t w a t e r f u n n e l
fro m t h e i n s o l u b l e m a t t e r , su c h a s f i l l e r s a s a l k a l i c a rb o n
a t e s . The f i l t r a t e i s t i t r a t e d w i t h N /10 HOI i n t h e p r e s e n c e
o f p h e n o l p h t a l e i n u n t i l t h e r e d c o l o r a p p e a r s . The f i l t e r
s h o u ld b e c o v e re d w i t h a w a t c h g l a s s i n o r d e r t o p r e v e n t th e
f o r m a t io n o f a l k a l i c a r b o n a t e th r o u g h c a r b o n d i o x id e from
t h e a i r .
T h is m eth o d , a s w i l l b e s e e n l a t e r , i s n o t s a t i s f a c
t o r y , s i n c e t h e f i l t e r p a p e r d o e s n o t o n ly a b s o r b f r e e a l k a l i ,
3
b u t a l s o a l k a l i w h ic h s h o u ld h a v e b e e n c o m b in e d . W ashing o f
th e f i l t e r , w h ic h i s n o t m e n tio n e d h e r e , w ou ld n o t rem ove
t h i s a l k a l i .
S e v e r a l o t h e r m eth o d s w h ic h p r e s c r i b e t h e u s e o f
b a riu m c h l o r i d e s o l u t i o n s a r e f r e q u e n t l y u s e d . B u t h e r e a
g r e a t e r r o r w i l l be i n t r o d u c e d , s i n c e b a r y t so a p h y d r o l y z e s
s l i g h t l y a n d a l s o a b s o r b s sodium h y d r o x id e . F u rth e r m o r e ,
t h e b a riu m c a r b o n a t e fo rm ed fro m t h e c a r b o n a t e s w i l l r e a c t
w i t h t h e N /10 HC1 and b a ry t; so a p w i l l b e p r e c i p i t a t e d w i t h
t h e f i l l e r s .
S t i l l o t h e r m e th o d s d e p en d o n t h e p r i n c i p l e o f s a l t
in g o u t w i t h sodium c h l o r i d e , b u t h e r e to o h i g h r e s u l t s w i l l
be o b t a i n e d . D r. D a v iso n 2 c la im e d t h a t h i s m ethod g i v e s
good r e s u l t s . I n t h i s m eth o d , w h ic h h a s b e e n a d o p te d b y t h e
W iz o ff ( W i s s e n s c h a f t l i c h e Z e n t r a l s t e l l e f u r 01 und F e t t -
f o r s c h u n g ) , 3 t o 5 gm. so a p a r e u s e d . T h is so a p i s d i s s o l v e d
i n 50 t o 75 m l 9 8 $ n e u t r a l i z e d a l c o h o l w h i l e w arm ing u n d e r a
r e f l u x c o n d e n s e r and t i t r a t e d , when c o o l , w i t h N /10 HC1. B u t
a l s o h e r e i t i s n o t c o n s i d e r e d t h a t t h e p r e s e n c e o f sodium
c a r b o n a t e w i l l i n t e r f e r e . T h is c a r b o n a t e i s m o s tly p r e s e n t
i n lo w e r g r a d e s o a p s .
The A n a l y t i c a l M ethods C om m ittee o f t h e S o c i e t y o f
% D a v iso n , "The M ethods o f D e te rm in in g o f ''F re e A l k a l i s '
an d t h e D e te r m in a tio n o f . t h e H y d r o l y t i c a l l y D i s s o c i a t e d A l k a l i
i n S o a p s , " R ayon and M e llia n d T e x t i l e M o n th ly . Y o l. XYI,
J a n u a r y , 1935, p . 55; F e b r u a r y , 1 93 5, p . 43.
4
P u b l i c A n a ly s ts and o t h e r A n a l y t i c a l C h e m is ts a p p o in t e d a
S u b -C o m m ittee t o i n q u i r e i n t o t h e m eth o d s f o r t h e d e te r m in a
t i o n o f u n s a p o n i f i a b l e m a t t e r i n o i l s an d o f u n s a p o n i f i e d
f a t i n s o a p s , a s w e l l a s th e d e t e r m i n a t i o n o f f r e e a l k a l i
an d f r e e f a t t y a c i d s . T h is S ub-C o m m ittee h a s exam ined th e
f o l l o w i n g m eth o d s f o r t h e d e t e r m i n a t i o n o f f r e e a l k a l i i n
< x
s o a p s f o r t h e p u r p o s e o f d e v e lo p in g a s a t i s f a c t o r y m eth o d ;
1 . The D e te r m in a tio n o f TOTAL F re e A l k a l i . V iz e r n and G u i l l o t .
(Ann. Chim. A n a l. 1934. 16, 4 4 6 .)
2. The D e te r m in a tio n o f F r e e C a u s tic A l k a l i .
a . The m ethod o f t h e B r i t i s h p h a rm a c o p o e ia . 1932.
b . The s t a n d a r d m eth o d o f t h e A m erican O il C h e m is ts '
S o c i e t y ( O il and S oap. 193 4 , 11, .9 0 .)
c . The s t a n d a r d m ethod o f th e German Soap M a n u f a c tu r e r s
A s s o c i a t i o n .
d . Y iz e r n an d G u i l l o t ’ s m eth o d ( l o c . c i t . )
e . P o e t h k e 's m eth o d (F e tte h e m . Umschau 193 5 , 42. 1 8 0 -2 ,
1 9 7 - 2 0 1 .)
f . M ethods u s i n g b a riu m c h l o r i d e , e . g . , R e p o r t No. T.G. 23.
G ovt. D e p t. S p e c i f i c a t i o n s f . Gen. S t o r e s . S o a p s, 1929.
(1) H eerm ann. (Chem. Z tg . , 1904, 2 8 , 53 and 6 0 .)
(A b s t. A n a ly s t 1 90 4 , 129. )
® A n a l y t i c a l M ethods C om m ittee: S u b -C o m m ittee on M ethods
o f Soap A n a l y s i s , R e p o rt No. 3 , "The D e t e r m in a t io n o f F re e
A l k a l i i n S o a p s / ' A n a l y s t . 6 2 :3 6 -4 1 , 1937.
5
(2) Is m a ls k e y . (D e u ts c h e 01 u n d F e t t In d . 1926,
4 6 , 5 4 5 -6 , 5 6 2 - 4 .)
(3) F ilin g , G onin an d F l o r e n t i n e . ( B u ll. S oc. Chim.
1914, 200. )
(4) H e tz e r . ( F e ttc h e m is c h e Um schau, 1935, 8 7 .)
g . M ethods d e p e n d in g on s a l t i n g o u t t h e so a p , f o llo w e d
b y t i t r a t i o n u s i n g s i l v e r n i t r a t e a s i n d i c a t o r .
(N ew in g to n , J . S . C . I . , 19 16, 3 5 , 9 5 .)
h . D a v iso n . (Chem. Um schau, 1926, 2 7 3 .)
3 . The d e t e r m i n a t i o n o f c a r b o n a t e . The p u b l i s h e d m e th o d s
d e p en d on t h e assum ed a l c o h o l i n s o l u b i l i t y o f t h e c a r b o n
a t e and t i t r a t i o n o f t h e r e s i d u e .
4. The M ethods o f S c o t t . ( S ta n d a r d M ethods o f C h e m ic a l A n a ly
s i s , v o l . 2. )
5.. The M ethod o f G r i f f i n . ( T e c h n ic a l M ethods o f A n a l y s i s ,
p . 3 7 1 .)
6. D a v is o n ’ s M ethod. (Rayon and M e llia n d T e x t i l e M o n th ly ,
16, I , 55. I I , 4 3 .)
The C om m ittee recom m ends t h e f o l l o w i n g p r o c e d u r e s :
1 . D i r e c t t i t r a t i o n w i t h o u t t h e a d d i t i o n o f b a riu m c h l o r i d e .
The p r o c e d u r e i s a s f o l l o w s : To 100 m l o f r e d i s t i l l e d
i n d u s t r i a l a l c o h o l ( 9 4 .7 $ v o l . ) i n a 400 m l f l a s k , add
0 .5 m l o f 0 .5 $ a l c o h o l i c p h e n o l p h t a l e i n s o l u t i o n , a ll o w t o
c o o l t o 70° G. a n d n e u t r a l i z e a t room t e m p e r a t u r e w i t h
6
N /lO N a l c o h o l i c KOH s o l u t i o n , add 10 gm. o f t h e so a p
i n t h i n s h a v in g s o r i n pow der and h e a t u n t i l i t i s d i s
s o l v e d . C ool t o 7 0 ° C. a n d t i t r a t e a t t h a t t e m p e r a t u r e
w i t h N /10 H2S04 .
2 . D i r e c t t i t r a t i o n w i t h t h e a d d i t i o n o f b a r iu m c h l o r i d e .
D i s s o lv e 10 gm. so a p i n 100 ml n e u t r a l i n d u s t r i a l a l c o h o l
c o n t a i n i n g 0 .5 m l o f 0 .5 $ p h e n o l p h t a l e i n s o l u t i o n . Add
5 m l o f h o t n e u t r a l 10$ a q u e o u s s o l u t i o n o f b a riu m c h l o
r i d e i n a t h i n s tr e a m , m ix t h o r o u g h ly , a n d t i t r a t e w i t h
N /10 HC1 a t 70° C. u n t i l t h e p in k c o l o r d is a p p e a r s *
The m eth o d s g i v e n i n S c o t t * s S ta n d a r d M ethods o f
C h e m ica l A n a ly s is ^ a r e a s f o l l o w s :
F re e A l k a l i o r F r e e F a t t y A cid
The m eth o d s o u t l i n e d w i l l n o t g iv e a b s o l u t e l y a c c u r a t e
r e s u l t s f o r f r e e a l k a l i , b u t w i l l g i v e r e s u l t s s u f f i
c i e n t l y a c c u r a t e f o r c o n t r o l o r p r a c t i c a l so a p a n a l y s e s .
The a c c u r a c y i s p r o b a b l y c l o s e t o -£ .0 1 $ NagO.
(a ) When " B u i l d e r s " ( o r F i l l e r s ) A re Low i n Amount an d
A re N ot D e te r m in e d ,— W eigh a 20 gm. sa m p le ( .0 5 ) r a p i d l y
and t r a n s f e r t o a 500 m l. E rle n m e y e r f l a s k c o n t a i n i n g
100 m l. o f h o t , n e u t r a l 95$ a l c o h o l . C o v er t h e f l a s k w i t h
a w a tc h g l a s s an d d i s s o l v e t h e soap a s r a p i d l y a s p o s s i b l e
b y h e a t i n g on t h e s te a m b a t h . Add a few d r o p s o f p h e n o l-
p h t h a l e i n an d t i t r a t e r a p i d l y w i t h N /4 HgS04 w i t h o u t
f i l t e r i n g . Take t h e f i r s t e n d p o in t , d i s r e g a r d i n g a n y
s u b s e q u e n t r e t u r n o f c o l o r . C a l c u l a t e t o f r e e NagO ( o r
NaOH) o r KgO ( o r KOH) a s t h e c h a r a c t e r o f t h e so a p i n d i
c a t e s . I f t h e a l c o h o l i c s o l u t i o n i s a c i d t o p h e n o l p h t h a l e i n ,
^ S c o t t *s S ta n d a r d M ethods o f C h e m ica l A n a l y s i s . N. H.
Furm an, e d i t o r , F i f t h E d i t i o n , (New Y ork: D. Van N o s tr a n d
Company, I n c . , 1 9 3 9 ), V o l. I I , p p . 2 0 3 2 -3 .
7
t i t r a t e w i t h N /10 NaOH and c a l c u l a t e t h e p e r c e n t a g e o f
f r e e f a t t y a c i d a s o l e i c a c i d , o r l a u r i c a c i d i f c o c o n u t
so a p . Save t h e s o l u t i o n f o r d e t e r m i n a t i o n o f c a r b o n a t e s .
(b) When ’’B u i l d e r s " A re D e te r m in e d .— ?7eigh a 10 .0 2 gm.
sam p le an d d i s s o l v e i n 200 m l. o f h o t , n e u t r a l 95$ a l c o h o l .
F i l t e r t h r o u g h a 9 cm. f i l t e r p a p e r i n t o a 500 m l. I r l e n -
m ey er f l a s k and w ash t h e r e s i d u e t h r e e t im e s w i t h h o t ,
n e u t r a l 95$ a l c o h o l . P r o t e c t fro m CO2 and o t h e r a c i d
fum es d u r i n g f i l t r a t i o n . I f t h e so a p c o n t a i n s b o r a x , o r
p h o s p h a t e s , i t c a n b e w ashed w i t h a l c o h o l i n d e f i n i t e l y
w i t h o u t re m o v in g th e a p p a r e n t a l k a l i n i t y . C o v e r t h e f l a s k
w i t h a w a tc h g l a s s an d h e a t t o i n c i p i e n t b o i l i n g . T i t r a t e
w i t h N /4 H2SO4 an d r e p o r t a s " f r e e Na20 ( o r NaOH)" o r
" f r e e K2O T o r KOH)" a s th e c h a r a c t e r o f t h e so a p i n d i c a t e s .
I f t h e a l c o h o l i s n o t p i n k , t i t r a t e w i t h N /10 NaOH and
r e p o r t " f r e e f a t t y a c i d " a s o l e i c a c i d .
As lo n g a s t h e a n a l y s i s d e a l s w i t h p r o p e r l y s a p o n i f i e d
s o a p s w i t h o u t f i l l e r s , an d w i t h so a p s i n w h ic h t h e r e a c t i o n
h a s g one t o c o m p le tio n , t h e e r r o r seem s t o be s m a ll, b u t i n
s o a p s n o t c o m p le te ly s a p o n i f i e d o r c o n t a i n i n g l a r g e am ounts
o f a l k a l i n e c a r b o n a t e s , o r so a p b u i l d e r s s u c h a s sodium p h o s
p h a t e , sod ium s i l i c a t e , b o r a x an d so d iu m s u l p h a t e , t h e e r r o r
w i l l b e g r e a t , even i f e q u i v a l e n t am o u n ts o f sodium and f a t t y
a c i d i o n s a r e p r e s e n t . The uncom bined sodium i o n s w i l l t a k e
up c h l o r i n e i o n s fro m N /10 HC1 and so i n t r o d u c e h ig h r e s u l t s .
A f u r t h e r d i s a d v a n t a g e i s t h a t t h e a l c o h o l i c s o l u t i o n
o f so diu m h y d r o x id e a b s o r b s c a rb o n d i o x i d e r e a d i l y fro m th e
a i r , e s p e c i a l l y w hen t h e s o l u t i o n i s w eak and i s c o o l i n g .
E x c lu s io n o f a i r i n t h i s r e s p e c t i s e s s e n t i a l t o p r e v e n t t h e
i n t r o d u c t i o n o f t h i s e r r o r .
S o ap s w h ic h a r e s a l t s o f w eak a c i d s and s t r o n g b a s e s
h y d r o ly z e a c c o r d i n g t o t h e d e g r e e o f d i l u t i o n and te m p e r a tu r e
i n t o f r e e f a t t y a c i d s an d a l k a l i h y d r o x id e s . The f i r s t
h y d r o l y s i s com ponent u n i t e s i n a q u e o u s s o l u t i o n a t room tem
p e r a t u r e w i t h t h e n o n - i o n i z e d so a p m o le c u le s t o fo rm a c i d
s a l t s w h ic h t h e n s e p a r a t e o u t . I t i s f o r t h i s r e a s o n t h a t
s o a p s o l u t i o n s r e a c t a l k a l i n e , b e c a u s e t h e l i b e r a t e d f a t t y
a c i d i s u s e d 'u p f o r t h e f o r m a tio n o f a c i d s o a p s . The same
p r i n c i p l e u n d e r l i e s t h e s o l u t i o n o f s o a p s i n a l c o h o l t o some
e x t e n t . The a c t u a l a l k a l i n i t y o f t h e so ap i s c a u s e d by
h y d r o l y s i s , b u t t h e f r e e a l k a l i n i t y c o n s i s t s o n ly o f t h e
e x c e s s f r e e a l k a l i .
C o n s id e r in g t h e a b o v e -m e n tio n e d d i f f i c u l t i e s an d d e f i
c i e n c i e s o f t h e d i f f e r e n t m e th o d s, t h i s i n v e s t i g a t i o n w as
c a r r i e d o u t w i t h t h e p u r p o s e o f t r y i n g t o d e v e lo p a b e t t e r
p r o c e d u r e o f a n a l y s i s f o r t h e d e t e r m i n a t i o n o f t h e f r e e a l k a l i
o r f r e e f a t t y a c i d s i n s o a p s — a p r o c e d u r e w h ich i s r a p i d and
w h ic h g i v e s s u f f i c i e n t l y a c c u r a t e p r a c t i c a l r e s u l t s . The
m e th o d s c h e c k e d w ere th e m ost commonly u s e d m e th o d s: t h e
m eth o d a d o p te d b y t h e W iz o ff ( W i s s e n s c h a f t l i e h e Z e n t r a l s t e l l e
f u r 01 und F e t t f o r s c h u n g ), t h e m eth o d g iv e n i n S c o t t ’ s S ta n d a r d
M ethods o f C h e m ica l A n a l y s i s , V o l. I I , and t h e m eth o d i n
G r i f f i n ’ s T e c h n ic a l M ethods o f A n a l y s i s , p . 371.
4 4
I v o r y s o a p , made b y P r o c t o r a n d Gamble, 99T0U$ p u r e ,
was u s e d a s s t a n d a r d . I v o r y so a p c o n s i s t s o f 25$ t a l l o w , 25$
o f c o c o n u t . o i l ^ . and 50$ h a rd e n e d f i s h o i l s . .T h is_ so a p _is_.more. _
d i f f i c u l t t o d i s s o l v e t h a n so a p s made o f low t i t e r o i l s , w hich
m o s t ly i n c l u d e o i l s o f lo w e r m o le c u la r w e ig h ts and a r e , a l s o ,
s t i l l m ore d i f f i c u l t t o f i l t e r . The s o l u t i o n s e t s im m e d ia te ly
t o a g e l on t h e c o ld f i l t e r p a p e r . F o r t h i s r e a s o n i t h a d t o
b e f i l t e r e d th r o u g h a h o t w a t e r b a t h .
T h is so a p was fo u n d to h a v e , a c c o r d in g t o th e W iz o ff
and S c o t t ’ s 'm e th o d s , 0 .0 2 4 $ f r e e a l k a l i . T h is a n a l y s i s was
r e p e a t e d b y b o i l i n g f o r 5 m in u te s u n d e r t h e r e f l u x e o n d e n s e r ,
f o r t h e r e a s o n g iv e n l a t e r , and t h e so a p was fo u n d t o c o n t a i n
0 .0 2 $ f r e e a l k a l i . A l l f u r t h e r c a l c u l a t i o n s and e x p e r im e n ts
w e re b a s e d on t h i s r e s u l t .
I t i s i m p o r t a n t , f o r t h e r e a s o n s a l r e a d y s t a t e d , t o
i n s u r e f i r s t c o m p le te s a p o n i f i c a t i o n o f t h e sa m p le b e f o r e
t i t r a t i o n o f th e e x c e s s a l k a l i . T h is i s r e a d i l y a c c o m p lis h e d
b y b o i l i n g i t u n d e r t h e r e f l u x c o n d e n s e r i n a l c o h o l . Dr.
H e tz e r h a s d e te r m in e d s a p o n i f i c a t i o n v a l u e s o f d i f f e r e n t
o i l s and f a t s , su c h a s t a l l o w , p a lm k e r n e l o i l , a r a c h i d o i l ,
so y a b e a n o i l , c o t t o n s e e d o i l , and h a rd e n e d f i s h o i l . He
b r o u g h t t h e m i x t u r e , c o n s i s t i n g o f f a t , a l c o h o l and a l c o h o l i c
p o t a s h s o l u t i o n , t o b o i l i n g and t i t r a t e d i t im m e d ia te ly . F o r
t h i s 2 1 /2 m in u te s w e re u s e d . N ext h e d e te r m in e d t h e s e
v a l u e s a t i n t e r v a l s a t 5, 10, 20 an d 30 m in u te s and fo u n d
t h e v a l u e s a s i n T a b le I .
® D r. H e t z e r , "The S a p o n i f i c a t i o n R a te o f F a t s and
O i l s an d i t s 'S ig n if ic a n c e " , f o r t h e " D e te r m in a tio n o f the" Tree""
A l k a l i i n S o a p ,” S e i f e n s i e d e r Z e i t u n g . 2 3 :4 6 3 , Ju n e 5 , 1935.
10
TABLE I
SAPONIFICATION VALUES OF SOME FATS AND OILS
AFTER DIFFERENT PERIODS OF BOILING
A c id S a p o n i f i c a t i o n v a lu e a f t e r :
1 ' ' " ■
M a t e r i a l V a lu e I n i t i a l
B o i l i n g
5 m in .
B o i l i n g
10 m in .
B o i l i n g
20 m in.
B o i l i n g
30 m in .
B o i l i n g
T a llo w 1.8 142 193 198 198 196
0 .9 $ 72$ 98$
100$
Mean: 197
100$ 100$
P a lm -
k e r n e l
O il
11.6
4 .8 $
172
70$
218
89$
242
99$
244
100$
244
100$
P e a n u t
F a t t y 1 2 0 .5 180 192 193 193 193
A c id s 63$ 93$ 9 9 .5 $
100$ 100$ 100$
S o y a b e an
O i l 19 129 184 190 190 1 8 9 .5
10$ 68$ 97$
100$ 100$ 100$
C o tto n
s e e d 2 .7 169 196 197 197 197
O il 1 .4 $ 86$ 99$
100$ 100$ 100$
C o con ut
O il 0 .7 218 252 259 257 258
0 .3 $ 84$ 98$
100$
Mean: 258
100$ 100$
H ard en ed
F i s h
O il
5 .9
3 .2 $
140
76$
179
97$
183
99$
185 185
100$ 100$
11
From t h i s , one c an s e e t h a t 10 m in u te s b o i l i n g a re
s u f f i c i e n t t o i n s u r e 100$ s a p o n i f i c a t i o n . B ut s i n c e t h e soap
i n t h e sam ple i s a l r e a d y s a p o n i f i e d an d t o p r e v e n t l o s s e s b y
a c t i o n on t h e g l a s s , 5 m in u te s * b o i l i n g w as assum ed t o be
s u f f i c i e n t f o r t h i s e x p e r im e n t.
To c h e c k th e e f f e c t o f a l k a l i c a r b o n a t e s on t h e a n a l y
s i s ■when f i l t e r i n g i s r e q u i r e d , and fro m t h e f a c t t h a t I v o r y
so a p i s a p u r e s o a p , s e v e r a l s a m p le s c o n t a i n i n g 1$ sodium
c a r b o n a t e w e re p r e p a r e d , to w h ich d i f f e r e n t am oun ts o f sodium
h y d r o x id e w e re added t o p ro d u c e t h e f r e e a l k a l i n i t y . The
f r e e a l k a l i c o n t e n t i n t h e so a p t h u s p r e p a r e d w as 0 .0 5 $ , 0 .1 $ ,
0 .2 $ , 0 .3 5 $ f r e e a l k a l i . T h is w as o b t a i n e d s im p ly b y a d d in g
t h e p r o p e r d i f f e r e n c e o f sodium h y d ro x id e i n t h e fo rm o f
N /10 NaOH s o l u t i o n t o t h e so a p and v a r y i n g t h e am ount o f t h e
s o a p . The f r e e a l k a l i c o n t e n t , i n o t h e r w o rd s , w as r a i s e d
i n t h e se c o n d e x p e rim e n t b y 0 .3 $ , i n t h e t h i r d b y 0 .0 8 $ , i n
t h e f o u r t h b y 0 .1 8 $ , e t c . T h is r e l a t i v e c o m p a ris o n , I b e l i e v e ,
i s s u f f i c i e n t l y a c c u r a t e t o p o i n t o u t t h e d e f i c i e n c y o f a n y
m eth o d w h ic h em ploys f i l t e r i n g , b e c a u s e t h e f i l t e r a b s o r b s
so d iu m h y d r o x id e . ( M i l l a r d and H a r k in s a l s o made d e te r m i n a
t i o n s o f s u r f a c e t e n s i o n b y r e l a t i v e c o m p a ris o n , u s i n g commer
c i a l s o a p s t o w h ic h d i f f e r e n t s a l t s h a d b e e n a d d ed , a n d n o t
b y s t a r t i n g w i t h c h e m ic a l l y p u r e s o a p s . )
The s i x d i f f e r e n t sa m p le s o f so a p w e re a n a ly z e d a c c o r d
in g t o t h e m e th o d s o f S c o t t , u s i n g f i l t e r i n g , a n d s i x o t h e r
la
sa m p le s t h e n w e re a n a ly z e d by s e p a r a t i n g t h e i n s o l u b l e r e s i
due b y c e n t r i f u g i n g . The r e s u l t s t h e n w e re co m p ared .
The m l N /10 NaOH w e re a d d e d t o 95 m l p r e v i o u s l y b o i l e d
a n d n e u t r a l i z e d a b s o l u t e a l c o h o l i n t h e p r e s e n c e o f 0 .5 m l
0 .5 $ p h e n o l p h t h a l e i n s o l u t i o n . The s o l u t i o n t h e n was m ade up
t o 100 m l w i t h w a t e r a n d a d d e d t o a w e ig h e d p r o p e r am ount o f
so a p i n a 150 m l b e a k e r . The sa m p le now c o rr e s p o n d e d t o
e x a c t l y 5 gm. o f s o a p . T h is w as d i s s o l v e d u n d e r h e a t i n g i n
t h e b e a k e r an d t h e n t r a n s f e r r e d im m e d ia te ly t o a 300 m l
E rle n m e y e r f l a s k . A r e f l u x c o n d e n s e r f i t t e d w i t h a c a lc iu m
c h l o r i d e t u b e w as a t t a c h e d , an d t h e m ix tu r e w as b o i l e d f o r
5 m in u te s a n d f i l t e r e d a t o n ce th r o u g h a 9 cm f i l t e r p a p e r ,
i n s e r t e d i n a h o t w a t e r f u n n e l , and w ashed w i t h t h r e e 50 m l
p o r t i o n s o f 95$ h o t n e u t r a l e t h y l a l c o h o l .
T h is e x p e r im e n t w as t h e n r e p e a t e d , w i t h th e e x c e p t i o n
t h a t t h e so ap w as n o t f i l t e r e d a s b e f o r e , b u t p o u re d i n t o a
100 m l c e n t r i f u g e tu b e k e p t warm i n a h o t t e m p e r a t u r e w a t e r -
b a t h , . and p l a c e d i n t o t h e c e n t r i f u g e and t h e i n s o l u b l e m a t t e r
w as th ro w n o f f . The c l e a r r e d l i q u i d was p o u re d o f f i n t o a
250 m l warmed E rle n m e y e r f l a s k an d im m e d ia te ly t i t r a t e d a t
70° C. The r e s i d u e w as sh a k e n w i t h a b o u t t e n 20 m l p o r t i o n s
o f h o t n e u t r a l a l c o h o l u n t i l i t w as c o l o r l e s s and p o u re d i n t o
a 250 ml E rle n m e y e r f l a s k , k e p t i n t h e w a t e r b a t h , and c o v e r e d
w i t h a c a lc iu m c h l o r i d e t u b e . T h is t h e n a l s o was t i t r a t e d a t
70° C. The t o t a l ml o f N /10 NaOH ?/ere r e c o r d e d i n T a b le I I .
TABLE I I
COMPARISON OP ACID VALUES OBTAINED BY FILTERING AND CENTRIFUGING
E x p e r i
m ent
( 1 )
F re e
A l k a li
C o n te n t
i n N /10
NaOH i n
O r i g i n a l
Soap
(2)
m l
N/10
NaOH
added
(3)
T o ta l
F re e
A l k a l i
i n
Sam ple
(4
F i l t e r M ethod C e n tr if u g e M ethod
m l I
- (E
HC1
1/10
>)
INaOH
P e r c e n t
age o f
C o rre s
po n d in g
F re e
A l k a l i
(6)
P e r c e n t
age o f
C o r re s
p o n d in g
F re e
Fatty-
A cid a s
O le ic
A cid
(7)
ml 1
(«
HC1
tylO
3)
NaOH
P e r c e n t
age o f
C o r re s
pon din g
F re e
A l k a li
(9)
P e r c e n t
age o f
C o r re s
p o n d in g
F re e
F a t t y
A cid as
O le ic
A cid
( 10)
1 0.02 0.00 0.02 0.20 0.1 0 .2 5 0.020
2 0 .4 0 0 .0 5 0.20 0.1 0 .2 5 0.020
3 1.00 0.10 0 .2 5 0 .1 4 1.10 0 .0 8 8
4 2 .3 0 0.20 0 .3 0 0 .0 2 4 2.20 0 .1 8
5 3 .5 0 0 .3 0 0 .6 0 0 .0 4 8 3 .4 0 0 .2 7
6 4 .2 5 0 .4 0 1.00 0 .0 8 0 4 .0 5 0 .3 2
1 m l N/10 NaOH = 1 m l N /10 HC1 = .0 2 8 2 g O le ic A cid = .0 0 4 g NaOH
14
Prom t h i s t a b l e we can s e e and p r o v e t h a t f i l t e r i n g
o f th e weak a l k a l i n e a l c o h o l i c soap s o l u t i o n i n t r o d u c e s g r e a t
e r r o r s . A c o m p a ris o n o f co lu m n s 3 , 5 , a n d 8 shows t h a t
N /10 NaOH was l o s t when t i t r a t e d b a c k . Columns 4, 6 / 7 , an d
9 /1 0 g i v e i n f o r m a t i o n o f t h e l o s s i n f r e e a l k a l i . The d i f
f e r e n c e m u st h a v e b e e n a b s o rb e d b y t h e f i l t e r p a p e r , w h ic h
r e t a i n s t h e i n s o l u b l e a l k a l i s a l t s and f i l l e r s . F o r t h i s
r e a s o n m eth o d s w h ic h p r e s c r i b e f i l t e r i n g s h o u ld be a b a n d o n e d ;
c e n t r i f u g i n g s h o u ld b e s u b s t i t u t e d f o r i t . Even i f t h i s d o e s
n o t g i v e t h e d e s i r e d s a t i s f a c t o r y r e s u l t s , a t l e a s t q u i t e
u s e f u l v a l u e s c a n t h u s b e o b t a i n e d .
A new m eth o d m aking u s e o f t h e c e n t r i f u g e w i l l be
g i v e n . T h is m ethod w i l l s e r v e t o d e te r m in e f r e e a l k a l i and
f r e e f a t t y a c i d s i n h a r d s o a p s , s o a p -p o w d e rs , an d o t h e r s o a p s
i n w h ic h b u i l d e r s a r e p r e s e n t , b y m eans o f o n l y one m eth o d .
I t w i l l e l i m i n a t e t h e n e c e s s i t y o f two m e th o d s , a s i s r e q u i r e d
6
i n S c o t t ’ s S t a n d a r d M ethods o f C h e m ica l A n a l y s i s .
The m ethod i s a s f o l lo w s : M easu re o u t i n a 400 m l
b e a k e r 95 m l e t h y l a l c o h o l , ad d 0 .5 ml 0 .5 $ p h e n o l p h t h a l e i n
s o l u t i o n , h e a t on th e e l e c t r i c h o t p l a t e t o b o i l i n g and n e u
t r a l i z e w i t h N /10 NaOH s o l u t i o n . D i s s o lv e im m e d ia te ly w i t h
t h i s n e u t r a l i z e d h o t a l c o h o l a 5 gm. sa m p le o f t h e so a p on
t h e h o t p l a t e an d b o i l u n d e r a r e f l u x c o n d e n s e r f o r 2 l / £
m in u t e s . F o u r t h i s s o l u t i o n i n t o a 100 m l c e n t r i f u g e tu b e
^ ££• a n t e . PP* 6 -7 .
15
which h a s b e e n k e p t warm i n a w a t e r b a t h , t o s e p a r a t e t h e
i n s o l u b l e m a t t e r . P o u r o f f t h e s u p e r n a t a n t l i q u i d a n d
t i t r a t e w ith N /10 NaOH o r N /10 HC1 t o t h e e n d p o in t a t 70° C . ,
h e a t i n g a g a i n i f n e c e s s a r y . S hake o u t t h e r e s i d u e w i t h
SO m l p o r t i o n s o f h o t n e u t r a l a l c o h o l , c e n t r i f u g i n g e a c h
tim e , an d p o u r t h e c l e a r s u p e r n a t a n t l i q u i d o f f i n t o a
250 m l E rle n m e y e r f l a s k w h ic h i s k e p t a t a p p r o x i m a t e ly 70° C.
and f i t t e d w i t h a c a lc iu m c h l o r i d e t u b e . When a t l e a s t t e n
20 m l p o r t i o n s o f h o t n e u t r a l a l c o h o l .h a v e b e e n c o l l e c t e d ,
o r when t h e s o l u t i o n i s c o l o r l e s s , a s i n t h e c a s e o f f r e e
a l k a l i n i t y , t i t r a t e a g a i n a t 70° C . , and add t h e r e s u l t i n
m l t o t h o s e fo u n d i n t h e f i r s t t i t r a t i o n , c a l c u l a t e , and
r e p o r t a s f r e e sodium h y d r o x id e o r f r e e f a t t y a c i d s .
16
SUMMARY
The d e t e r m i n a t i o n o f t h e f r e e a l k a l i an d f r e e f a t t y
a c i d s i n s o a p s i s an im p o r ta n t q u e s t i o n , b e e a u s e i t e n a b l e s
t h e so ap m a n u f a c t u r e r t o c o n t r o l t h e am ount o f f r e e a l k a l i
w h ic h s h o u ld b e p r e s e n t t o p r e v e n t r a n c i d i t y i n s o a p s .
D e s p i t e t h e v a s t am ount o f l i t e r a t u r e e s t a b l i s h e d and t h e
e f f o r t s made b y t h e many i n v e s t i g a t o r s , t h i s p ro b le m
re m a in e d one o f t h e o b s c u r e f a c t s i n so a p i n d u s t r y .
Many m e th o d s h a v e b e e n recom m ended b a s e d on s e p a r a t
in g t h e a l c o h o l i n s o l u b l e m a t t e r by f i l t e r i n g o r p r e c i p i t a t
in g t h e c a r b o n a t e s w i t h b a riu m c h l o r i d e , o r s a l t i n g o u t o f
t h e so ap and t h e n s u b s e q u e n t t i t r a t i o n . B ut i t i s im p o s s i
b l e t o o b t a i n r e l i a b l e r e s u l t s by an y one o f t h e s u g g e s te d
m e th o d s f o r s e v e r a l r e a s o n s : t h e s o a p may n o t b e c o m p le te ly
s a p o n i f i e d , t h e so ap h y d r o l y z e s , c a rb o n d i o x i d e i s a b s o rb e d
by t h e h o t a l c o h o l i c a l k a l i n e s o l u t i o n , and f i l t e r p a p e r
a b s o r b s f r e e a l k a l i .
C o n s id e r in g t h e s e d i f f i c u l t i e s , t h i s i n v e s t i g a t i o n
w as c a r r i e d o u t w i t h t h e p u r p o s e o f d e v e lo p in g a b e t t e r p r o
c e d u re o f a n a l y s i s w h ic h i s r a p i d an d g i v e s r e l i a b l e p r a c
t i c a l r e s u l t s .
I v o r y so ap was c h o s e n a s c o m p a r a tiv e s t a n d a r d . D i f
f e r e n t am ounts o f f r e e a l k a l i w ere a d d ed t o tw e lv e d i f f e r e n t
s a m p le s , and t h e s e w ere a n a ly z e d by two m e th o d s. S ix w ere
17
a n a ly z e d b y t h e m eth o d g iv e n i n S c o t t ’ s S ta n d a r d M ethods o f
C h e m ica l A n a l y s i s , u s i n g f i l t e r i n g , and t h e o t h e r s i x b y a
m ethod e m p lo y in g c e n t r i f u g i n g f o r t h e s e p a r a t i o n o f t h e
i n s o l u b l e m a t t e r . A c o m p a ris o n o f t h e d a t a o b t a i n e d showed
t h a t t h e f i l t e r m ethod g a v e i n a c c u r a t e r e s u l t s . I n t h r e e
c a s e s ev en f r e e f a t t y a c i d w as fo u n d i n s t e a d o f f r e e a l k a l i .
On t h e o t h e r h a n d , c l o s e r r e s u l t s w ere o b t a i n e d b y c e n t r i
f u g i n g . The f i l t e r p a p e r a b s o r b s f r e e a l k a l i t o a l a r g e
e x t e n t .
A new m eth o d b a s e d on s e p a r a t i n g o f t h e a l c o h o l
i n s o l u b l e m a t t e r b y c e n t r i f u g i n g w as d e v e lo p e d .
BIBLIOGRAPHY
BIBLIOGRAPHY
A llg e m e in e 01 und F e t t Z e i t u n g . 3 8 :4 0 9 (1 9 3 5 ). Th. Ruem le,
" F re e and A c t u a l Soap A l k a l i . ”
A m erican P e r f u m e r . 2 9 :4 0 3 - 4 , O c to b e r, 1934. K n ig g e ," D e te rm i
n a t i o n o f ’F re e A l k a l i ’ in S o a p s.”
A n a l y s t . 6 2 :3 6 -4 1 , 1937. A n a l y t i c a l M ethods C om m ittee: Sub
c o m m itte e on M ethods o f Soap A n a l y s i s , R e p o r t No. 3,
"The D e te r m in a tio n o f F re e A l k a l i i n S o a p s . "
J o u r n a l A m e ric an C h e m ic a l S o c i e t y . 5 9 :2 6 4 4 -7 (1 9 3 7 ). A. R.
O lson and R. S. H a l f o r d , "The R a te and M echanism o f
H y d r o l y s i s o f T e r t i a r y B u ty l C h l o r i d e . ”
K o l l o r d B e i h e f t e , 4 5 :2 5 3 -3 0 2 (1 9 3 7 ). L o t t e r m o s e r an d G hose,
’• P o te n ti o m e t r i c T i t r a t i o n s o f Sodium S a l t s o f F a t t y A c id s .
Rayon and M e llia n d T e x t i l e M o n th ly . V o l. XVI, J a n u a r y , 1935,
p . 55; F e b r u a r y , 1935, p . 43. D a v is o n , "The M ethods o f
D e te r m in in g o f ’ F re e A l k a l i s .’ ”
S e i f e n s i e d e r Z e i t u n g . 6 2 :4 6 3 -4 (1 9 3 5 ). D r. H e t z e r , ”The
S a p o n i f i c a t i o n R a te o f F a t s and i t s S i g n i f i c a n c e f o r t h e
D e t e r m in a t io n o f t h e f r e e a l k a l i i n S o a p s . "
S e i f e n s i e d e r Z e i t u n g . 6 1 :7 7 2 -3 (1 9 3 4 ). G. E n ig g e , ”The
D e te r m in a tio n o f F r e e A l k a l i i n S o a p s . ”
T r a n s . F a ra d a y S o c i e t y . 3 1 :1 5 3 - 6 4 (1 9 3 5 ). M. E. L a in g ,
M cBaln, d e l a t i o n o f l l e c t r o k i n e t i c and E l e c t r o l y t i c
M ovement, a s I l l u s t r a t e d by th e T r a n s p o r t o f E l e c t r i c i t y
th ro u g h Soap A c i d s . ”
Z e i t s c h r i f t f u r A n a l y t i s c h e C h em ie. 105 B and, 7 u nd 8 H e f t,
p . 269. H. B a g g e s g a a rd -R a sm u ss e n , " T i t r a t i o n sc h w a c h e r
S a u re n und B asen i n W a s s e r -A lc o h o l- G e m is c h e n .”

Asset Metadata

Creator Schubert, W. O (author)

Core Title The determination of free alkali or free fatty acids in soaps

Contributor Digitized by ProQuest (provenance)

Degree Master of Science

Degree Program Chemistry

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

Tag chemistry, organic,oai:digitallibrary.usc.edu:usctheses,OAI-PMH Harvest

Language English

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c17-788404

Unique identifier UC11347814

Identifier EP41519.pdf (filename),usctheses-c17-788404 (legacy record id)

Legacy Identifier EP41519.pdf

Dmrecord 788404

Document Type Thesis

Rights Schubert, W. O.

Type texts

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...

Repository Name University of Southern California Digital Library

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