Thermodynamic Behavior of Electrolytes in Mixed SolventsâII

12 Ternary System Phase Diagram Determinations Concerning Potassium Electrolyte Influence on Aqueous Solutions of Dioxane or Downloaded by UNIV OF ARIZONA on October 8, 2015 | http://pubs.acs.org Publication Date: June 1, 1979 | doi: 10.1021/ba-1979-0177.ch012

Tetrahydrofuran JOHN A. McNANEY Department of Chemistry, Fitchburg State College, Fitchburg, MA 01420 HOWARD K. ZIMMERMAN and PAUL H. GROSS Department of Chemistry, University of the Pacific, Stockton, CA 95211

Phase diagrams, at 25°C, were determined for potassium acetate-water-dioxane, potassium acetate-water-tetrahydrofuran, and potassium chloride-water-tetrahydrofuran. Po tassium acetate exceeded potassium chloride in its capacity to stratify aqueous solutions of either dioxane or tetrahydro furan. Kobsev's (1) investigations revealed that the greater the solubility of an alkali metal salt, the greater its salting -out effect. The relative order of the water solubilities of the salts studied are potassium acetate >> potassium chloride. More potassium acetate is required to cause stratification in aqueous dioxane than is necessary to obtain the same results in aqueous tetrahydrofuran. It is proposed that, in com parison to dioxane, tetrahydrofuran forms a weaker associa tion with water and, hence, the cations can more easily break these bonds causing liquid-phase separation.

H p h e p h e n o m e n a w h i c h gave rise to this s t u d y w e r e first b r o u g h t to t h e χ

a t t e n t i o n of Η . K . Z i m m e r m a n , D i r e c t o r o f C a r b o h y d r a t e R e s e a r c h a t

t h e U n i v e r s i t y o f t h e Pacific, b y r e s e a r c h w o r k e r s i n p e p t i d e c h e m i s t r y w h e r e t h e p o t a s s i u m h y d r o x i d e - w a t e r - d i o x a n e system w a s u s e d i n t h e saponification o f esters.

H e d i r e c t e d that this m e t h o d b e u s e d b y h i s

0-8412-0428-4/79/33-177-177$05.00/l © 1979 American Chemical Society In Thermodynamic Behavior of Electrolytes in Mixed Solvents—II; Furter, W.; Advances in Chemistry; American Chemical Society: Washington, DC, 1979.

178

T H E R M O D Y N A M I C BEHAVIOR OF E L E C T R O L Y T E S

staff to s a p o n i f y suger acetates

a n d benzoates.

T h e y also f o u n d

a m i n o s u g a r d e r i v a t i v e s , e v e n h y d r o c h l o r i d e s of a m i n o s u g a r could

be

extracted

from

concentrated

aqueous

II

that

glycosides,

potassium

chloride

solutions. I n u s i n g this s a p o n i f i c a t i o n p r o c e d u r e a salting-out of d i o x a n e often was observed.

S i n c e s u c h a s a l t i n g - o u t effect c a n b e q u i t e t r o u b l e s o m e ,

it b e c a m e necessary to i n i t i a t e a s t u d y of t h e t h r e e - c o m p o u n d system i n o r d e r to l e a r n h o w s u c h a c o m p l i c a t i o n m i g h t be a v o i d e d . It w a s also h i g h l y d e s i r a b l e to l e a r n h o w to better c o n t r o l the s a l t i n g o u t effect i n w a t e r - t e t r a h y d r o f u r a n systems so t h a t extractions i n this Downloaded by UNIV OF ARIZONA on October 8, 2015 | http://pubs.acs.org Publication Date: June 1, 1979 | doi: 10.1021/ba-1979-0177.ch012

p a i r of m i x e d solvents c o u l d b e p e r f o r m e d .

T h i s present s t u d y of the

p h a s e r e l a t i o n s h i p s i n some of the solvent systems u s e d i n a m i n o s u g a r r e s e a r c h i n c l u d e s t h e d e t e r m i n a t i o n of the phase d i a g r a m s of t h e systems potassium

acetate-water-dioxane,

potassium

acetate-water-tetrahydro-

f u r a n , a n d p o t a s s i u m c h l o r i d e - w a t e r - t e t r a h y d r o f u r a n , a n d a n a t t e m p t to p r o v i d e a t h e o r e t i c a l e x p l a n a t i o n for the e x p e r i m e n t a l results. Experimental Chemicals. P o t a s s i u m acetate f r o m J . T . B a k e r C h e m i c a l C o m p a n y ( B a k e r A n a l y z e d R e a g e n t , 9 9 . 0 % assay) w a s u s e d i n C 0 - f r e e d i s t i l l e d w a t e r a n d w a s s t a n d a r d i z e d w i t h s t a n d a r d p e r c h l o r i c a c i d i n g l a c i a l acetic a c i d , u s i n g m e t h y l v i o l e t i n d i c a t o r (2). P o t a s s i u m c h l o r i d e of B a k e r A n a l y z e d R e a g e n t , 9 9 . 9 % assay, w a s u s e d as r e c e i v e d . 1,4-Dioxane of technical grade from J. T . B a k e r C o m p a n y was purified by distillation o v e r m e t a l l i c s o d i u m as d e s c r i b e d b y V o g e l ( 3 ) . Tetrahydrofuran ( T H F ) of B a k e r A n a l y z e d R e a g e n t , d e n s i t y 0.881 g c m " , b o i l i n g r a n g e 6 5 . 8 ° - 6 6 . 4 ° C , w a s u s e d as r e c e i v e d . K a r l F i s c h e r R e a g e n t , o b t a i n e d f r o m A l l i e d C h e m i c a l C o m p a n y , w a s s t a n d a r d i z e d to 1 m L of r e a g e n t to react w i t h at least 5 m g of w a t e r . F i s h e r c e r t i f i e d s t a n d a r d w a t e r i n methanol (1 m L = 1 m g H 0 ) , used for standardizing K a r l F i s c h e r R e a g e n t , w a s o b t a i n e d f r o m F i s h e r Scientific C o m p a n y . 2

3

2

Apparatus. A c i r c u l a t i n g c o n s t a n t - t e m p e r a t u r e w a t e r b a t h e q u i p p e d w i t h a micro-set t h e r m o r e g u l a t o r w a s u s e d to s u p p l y the w a t e r f o r the jacket of a P y r e x w a t e r - j a c k e t e d r e a c t i o n flask t h a t w a s e q u i p p e d w i t h a m a g n e t i c stirrer. B u r e t s u s e d — a u t o m a t i c a n d c o n v e n t i o n a l — w e r e of Class-Α g r a d e a n d e q u i p p e d w i t h T e f l o n stopcocks. General Procedure. T h e s e l e c t e d e l e c t r o l y t e s o l u t i o n w a s p l a c e d i n the j a c k e t e d r e a c t i o n flask w h i c h w a s h e l d at constant t e m p e r a t u r e b y the c o n n e c t e d c i r c u l a t i n g w a t e r b a t h . T h e t i p of a b u r e t c o n t a i n i n g the c y c l i c ether w a s i n t r o d u c e d t h r o u g h a stopper i n t o t h e m o u t h of t h e r e a c t i o n flask. W i t h the electrolyte s o l u t i o n u n d e r g o i n g constant s t i r r i n g the c y c l i c ether w a s d e l i v e r e d s l o w l y f r o m the b u r e t into the r e a c t i o n flask to the p o i n t of t u r b i d i t y or p r e c i p i t a t i o n , a n d t h e d e l i v e r e d v o l u m e of c y c l i c ether w a s n o t e d . T h e densities of the c y c l i c ethers ( d i o x a n e a n d T H F ) a n d of the electrolyte solutions u s e d h a d b e e n d e t e r m i n e d p r e v i o u s l y ; t h e n o r m a l i t i e s o f t h e electrolyte solutions w e r e k n o w n . W i t h these d a t a , t h e v o l u m e m e a s u r e m e n t of e a c h of the c o m p o n e n t s of the m i x t u r e w a s

In Thermodynamic Behavior of Electrolytes in Mixed Solvents—II; Furter, W.; Advances in Chemistry; American Chemical Society: Washington, DC, 1979.

12.

MCNANEY E T AL.

Phase Diagram

179

Determinations

c o n v e r t e d to w e i g h t d a t a . T i e - l i n e s w e r e e s t a b l i s h e d b y s e l e c t i n g m i x t u r e s w h o s e c o m p o n e n t c o m p o s i t i o n s w o u l d l i e i n a m u l t i p h a s e r e g i o n of t h e p h a s e d i a g r a m , a n d t h e n a n a l y z i n g e a c h p h a s e of t h e m i x t u r e f o r its c o m p o n e n t s after e q u i l i b r i u m h a d b e e n a c h i e v e d Specific Procedure. T a b l e I p r o v i d e s a c h a r a c t e r i s t i c e x a m p l e of t h e d a t a f o r t h e e x p e r i m e n t a l observations i n t h e system p o t a s s i u m a c e t a t e w a t e r - d i o x a n e , w h i c h d a t a w e r e u s e d i n p l o t t i n g s o l u b i l i t y c u r v e s at 25 ° C and 85°C on a three-component, equilateral triangular g r a p h ( F i g u r e 1 ) .

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Table I . Solubility C u r v e and Tie-Line Data for the System Potassium Acetate—Water—Dioxane in Weight Percentage Solubility

Curve

Data

25°C

KC H Og t

Η,Ο

s

0.33 0.53 5.14 8.68 15.50 24.35 29.93 72.00 71.00 ' 74.00 72.93 ° 20

>c

300

21.45 23.00 24.15 25.60 26.80 26.34 (20)

71.50 70.70 72.10 73.00 72.90

Liquid-Liquid

HO

Less Dense

7.90 13.20 16.20

68.40 73.60 73.30

CiHsO

t

23.70 13.20 10.50 Original

HO

KCl

HO

5.00 10.05 9.97

50.00 59.95 50.05

HO

0.01 0.00 0.00

13.80 9.95 8.72

23.20 24.10 24.95

71.10 71.50 71.70

45.00 30.00 39.98 Equilibrium

8

5.70 4.40 3.35

H0

34.99 31.10 37.00

60.04 65.00 59.98

22.60 22.70

71.00 70.93

CH0

t

k

s

4.97 3.90 3.02

Equilibrium Less Dense

CiHsO

t

Complex

KCl

Denser Layer HO

86.19 90.05 91.28

s

Solid-Liquid-Liquid

KCl

8

CiH O

Original t

CiH 0

t

t

CH 0

t

Layer

KCl

Solution

KCl

7.05 6.30 3.75 1.40 0.00

Mixture

Solid-Liquid Saturated

CiHsO

Equilibrium

Layer

KCl

Equilibrium

6.40 6.37 Original

Layer

KCl

HO

C # 0

0.00 0.00 0.00 0.00

6.00 6.10

94.00 93.90

t

4

Complex

KCl

HO

35.05 25.00

49.93 50.03

t

CiHsO 15.02 24.97


8

184

T H E R M O D Y N A M I C BEHAVIOR O F E L E C T R O L Y T E S

II


.KOAc

TETRAHYDROFURAN

HO H Figure 2.

Isotherm of potassium acetate-water-THF

in weight percent

W h e n e x t r a p o l a t e d , a l l o f these straight lines m e t , a p p r o x i m a t e l y , i n a p o i n t , t h e c o m p o s i t i o n of t h e d i s s o l v e d p o t a s s i u m c h l o r i d e i n t h e s a t u r a t e d s o l u t i o n ( 6 ) . T h e s e plots are s h o w n i n F i g u r e 3. T h e m o d i f i c a t i o n of S c h r e i n e m a k e r s w e t r e s i d u e m e t h o d w h i c h w a s u s e d i n this p a r t o f the i n v e s t i g a t i o n is that i n s t e a d o f a n a l y z i n g t h e w e t r e s i d u e , a c o m p l e x is p r e p a r e d o f k n o w n c o m p o s i t i o n a n d t h e s o l u t i o n o n l y is a n a l y z e d . T h i s a g a i n gives t w o p o i n t s o n the d i a g r a m : t h e s o l u t i o n p o i n t o n the c u r v e a n d the c o m p l e x p o i n t w h i c h replaces the w e t r e s i d u e p o i n t . H i l l a n d R i c c i ( 7 ) c l a i m that the c o m p l e x m e t h o d i s as a c c u r a t e or more accurate than t h e residue method i f algebraic extrapolation of t h e tie-lines is u s e d . A s s u m e the s y n t h e t i c c o m p l e x t o b e : C o m p o u n d A — 2 0 % , C o m p o u n d Β

(Water)—30%,

dioxane—50%.

T h e solution

o n analysis

Compound A — 4 % , Compound B — 1 6 % , dioxane—80%. dioxane contain 4 A +

gives:

T h e 80 p a r t s

1 6 B a n d 50 parts dioxane contain 2.5A - f 10B.

T h i s a m o u n t o f s o l u t i o n is s u b t r a c t e d f r o m the c o m p l e x g i v i n g : 20 30 -

2.5 — 17.5A 10.0 = 2 0 . 0 B

ι

37.5 t o t a l


12.

McNANEY ET AL.

Phase Diagram

185

Determinations

T h u s , i f a l l the d i o x a n e c o u l d b e r e m o v e d f r o m the c o m p l e x as s o l u t i o n , the residue w o u l d be: 4 6 . 7 % A a n d 5 3 . 3 % B . T h i s point, w h e n m a r k e d o n t h e e d g e of the d i a g r a m , gives t h e correct e x t r a p o l a t i o n of the c o m p l e x p o i n t . I t does n o t necessarily represent a n y e x i s t i n g s o l i d phases, b u t the l i n e j o i n i n g this p o i n t to t h e s o l u t i o n p o i n t m u s t pass t h r o u g h t h e t r u e solid phase ( 8 ) .

I n t h i s i n v e s t i g a t i o n , h o w e v e r , a l l extrapolations e n d e d

w i t h the s o l i d p h a s e as p u r e p o t a s s i u m c h l o r i d e at one c o r n e r , i.e., A 100%, Β =

=

0%.

Invariant Point Confirmation. T h e w e i g h t percentages

of t h e p r e

p a r e d complexes, a r b i t r a r i l y c h o s e n w i t h i n t h e three-phase, s o l i d - l i q u i d Downloaded by UNIV OF ARIZONA on October 8, 2015 | http://pubs.acs.org Publication Date: June 1, 1979 | doi: 10.1021/ba-1979-0177.ch012

l i q u i d r e g i o n , are t a b u l a t e d i n T a b l e I I I . T a b u l a t e d i n t h e same t a b l e are the w e i g h t percentages of the denser l i q u i d layers a n d those of t h e less dense layers. P l o t s of e a c h set of d a t a — p r e p a r e d c o m p l e x , denser l a y e r , a n d less dense l a y e r — w e r e m a d e

o n the g r a p h w h i c h a l r e a d y c o n t a i n e d

the

s o l u b i l i t y c u r v e a n d tie-lines. A s t r a i g h t l i n e w a s d r a w n f r o m the p r e p a r e d c o m p l e x p o i n t to its denser l a y e r p o i n t a n d , s i m i l a r l y , f r o m the c o m p l e x

Figure

3.

Isotherm of potassium chloride-water-THF in weight (invariant point: 22.6% KCl, 71.0% H 0, 6.4% THF) 2


percent

186

T H E R M O D Y N A M I C BEHAVIOR O F E L E C T R O L Y T E S

II

p o i n t to the less dense l a y e r p o i n t . T h i s f o r m e d a n a n g l e w i t h the c o m p l e x p o i n t as the vertex. T h e ends of t h e t w o sides, denser l a y e r p o i n t a n d less dense l a y e r p o i n t , f e l l o n the s o l u b i l i t y c u r v e w i t h t h e denser

point

a p p r o x i m a t e l y o n t h e i n v a r i a n t p o s i t i o n . A p l o t of the other set of d a t a g a v e s i m i l a r results. T h i s denser l a y e r p o i n t also c o i n c i d e d w i t h

the

i n v a r i a n t p o i n t , c o n f i r m i n g i t , w h i l e the less dense l a y e r p o i n t f e l l almost e x a c t l y o n the p r e v i o u s l y p l o t t e d less dense l a y e r p o i n t . T h e s e plots m a y b e f o u n d i n F i g u r e 3.


Discussion of

Results

D i o x a n e i n a n aqueous s o l u t i o n is associated w i t h w a t e r also

(9,10,11,

E v i d e n c e that T H F behaves i n a l i k e m a n n e r has b e e n r e p o r t e d

12,13).

(14). A c c o r d i n g to G o d n e v a a n d K l o c h o (13),

w h e n a n electrolyte is a d d e d

to w a t e r - d i o x a n e or w a t e r - T H F , t w o phases result. I n o r d e r to b r i n g a b o u t this s e p a r a t i o n , the w a t e r - c y c l i c ether association m u s t b e b r o k e n d o w n . T h e s e authors b e l i e v e t h a t t h e h y d r a t i o n of t h e e l e c t r o l y t e cations is a c c o m p l i s h e d b y the d e h y d r a t i o n of the c y c l i c ether m o l e c u l e s , c a u s i n g stratification. Salting-Out Effects O w i n g to Potassium Acetate. T h e system p o t a s sium acetate-water-dioxane

( F i g u r e 1, T a b l e I )

t e m p e r a t u r e s of 2 5 ° C a n d 8 5 ° C .

was investigated at

T h e s a l t i n g - o u t isotherms are b i n o d a l

curves a n d s h o w e d a v e r y s l i g h t d i s p l a c e m e n t t o w a r d the a q u e o u s c o r n e r w i t h a n increase i n t e m p e r a t u r e . The

l i q u i d layer formation

(at

25°C)

of t h e s y s t e m

a c e t a t e - w a t e r - T H F is also a b i n o d a l c u r v e ( F i g u r e 2 ) .

potassium

There is, h o w

ever, a s u b s t a n t i a l difference b e t w e e n the l a y e r i n g effect o n t h e w a t e r d i o x a n e b y p o t a s s i u m acetate c o m p a r e d w i t h its effect o n t h e w a t e r - T H F mixture. bring

I n the l a t t e r case, m u c h less p o t a s s i u m acetate is r e q u i r e d to

about

separation into two

liquid

phases

than with

the

same

p e r c e n t a g e c o m p o s i t i o n of w a t e r - d i o x a n e . E v e n w h e n p l o t t e d o n a m o l e p e r c e n t a g e c o m p o s i t i o n basis (see pronounced,

s t i l l exists.

F i g u r e 4 ) this difference, w h i l e less

O n e c o u l d c o n c l u d e t h a t the reason f o r this

b e h a v i o r rests i n the fact that T H F has o n e - h a l f as m a n y o x y g e n sites for h y d r o g e n b o n d i n g t h a n does d i o x a n e , a n d thus c a n h o l d less w a t e r i n association.

Previous experimenters, however,

have

produced

results

w h i c h seem to b e l i e this. It has b e e n p o s t u l a t e d b y different groups of investigators that the m o l e c u l a r r a t i o f o r w a t e r : T H F is 17:1 (15,16),

as

c o m p a r e d w i t h 2 : 1 , 3 : 1 , a n d 4:1 for the m o l e c u l a r r a t i o of w a t e r : d i o x a n e association, as p u t f o r t h b y others (10,11).

T h i s s t u d y has d e t e r m i n e d

that a b o u t three times as m u c h p o t a s s i u m acetate, i n m o l e

percentage,

is r e q u i r e d to cause stratification i n d i o x a n e t h a n is necessary to o b t a i n


12.

Phase Diagram

McNANEY ET AL.

187

Determinations

Dioxane Q Tetrahydrofuran

Δ


Mole % KOAc

HOH

10

30

20

40

Mole % D i o x a n e , Mole % T e t r a h y d r o f u r a n

»

Figure 4. Comparison of potassium acetate-water-dioxane and potassium acetate-water-THF plots: Θ, dioxane; Δ , THF

t h e same results i n T H F w h e n b o t h solvents are i n aqueous

solutions.

I f T H F associates w i t h m o r e w a t e r t h a n does d i o x a n e , i t w o u l d

seem

that the opposite should be true. T h e investigators i n v o l v e d i n t h i s s t u d y f e e l that i t is reasonable to c o n c l u d e t h a t c o m p a r e d w i t h d i o x a n e , T H F f o r m s a w e a k e r association w i t h w a t e r a n d , h e n c e , the cations c a n m o r e easily b r e a k these b o n d s c a u s i n g l i q u i d - p h a s e s e p a r a t i o n . T h e basis f o r this j u d g m e n t rests w i t h the a s s u m p t i o n t h a t 17 w a t e r m o l e c u l e s w o u l d b e h e l d less firmly b y one T H F m o l e c u l e t h a n f o u r w a t e r m o l e c u l e s b y one d i o x a n e m o l e c u l e . Salting-Out

Effect

Owing

to

Potassium Chloride.

Kobzev

(I)

m a i n t a i n e d , i n a s t u d y of salts of p o t a s s i u m , s o d i u m , U t h i u m , r u b i d i u m , a n d c e s i u m ( a l l i n aqueous s o l u t i o n s ) , t h a t t h e s o l u b i l i t y of a salt i n w a t e r w a s r e l a t e d to its s a l t i n g - o u t effect. H e f o u n d t h a t salts w i t h t h e s o l u b i l i t y f r o m 6.4 to 2.8 g e q u i v w t p e r 100 m L of w a t e r at 2 5 ° C c a u s e d stratifica t i o n i n a l l systems e x c e p t w a t e r - m e t h a n o l a n d w a t e r - e t h a n o l . Salts w i t h s o l u b i l i t i e s b e l o w 2.82 g e q u i v w t d i d not cause s a l t i n g - o u t . T h e r e l a t i v e w a t e r s o l u b i l i t i e s of p o t a s s i u m acetate > >

the t w o

salts i n v e s t i g a t e d

are

p o t a s s i u m c h l o r i d e . A s one m i g h t expect, t h e n ,

p o t a s s i u m acetate has t h e greater c a p a c i t y to salt-out aqueous

solutions

of d i o x a n e a n d T H F . P o t a s s i u m c h l o r i d e c a n n o t b r i n g a b o u t s a l t i n g - o u t t h r o u g h t h e f u l l p e r c e n t a g e c o m p o s i t i o n r a n g e of the t e r n a r y m i x t u r e .


188

THERMODYNAMIC

Potassium chloride a n d potassium

BEHAVIOR

OF ELECTROLYTES

II

acetate w e r e i n s o l u b l e i n b o t h

d i o x a n e a n d T H F . T h e s o l u b i l i t y o f these salts i n w a t e r w a s a s c e r t a i n e d and compared

very closely w i t h the literature

values cited i n Tables

I and III. E . C h u l i k has assisted i n the f o r e g o i n g w o r k b y d e v e l o p i n g a n a l y t i c a l m e a n s f o r q u a n t i t a t i v e d e t e r m i n a t i o n o f acetate salts as m o d i f i c a t i o n s o f the m e t h o d o f D . C e a u s e s c u ( 1 7 ) .


Literature Cited 1. Kobsev, V. V., Sb. Nauchn. Rab. Aspir. L'vov. Politekh. Inst. (1961) 21. 2. Fritz, J. S., "Acid Base Titrations in Nonaqueous Solvents," G. Frederick Smith Chemical Co., Columbus, Ohio, 1952. 3. Vogel, A. I., "A Text Book of Practical Organic Chemistry," 3rd ed., p. 177, Longmans, Green and Co., New York, 1957. 4. Mitchell, J., Smith, D. M., "Aquametry, Chemical Analysis," Vol. V, Interscience, New York, 1948. 5. Blaedel, W. J., Meloche, V. W., "Elementary Quantitative Analysis," p. 278, Row, Peterson and Co., White Plains, 1957. 6. Schreinemakers, F. Α. H., Z. Phys. Chem. Leipzig (1893) 11, 81. 7. Hill, A. E., Ricci, J. E., J. Am. Chem. Soc. (1931) 53, 4305. 8. Purdon, F. F., Slater, V. W., "Aqueous Solutions and the Phase Diagram," p. 65, Edward Arnold and Co., London, 1946. 9. Zimmerman, H. K., Bull. Soc. Chim., Beograd (1959) 24, 1. 10. Schott, H., J. Chem. Eng. Data (1961) 6, 19. 11. Tsypin, M. Z., Trifonov, Ν. Α., Tr. Kazan. Khim.-Tecknol.Inst.im S. M. Kirova (1958) 22, 120. 12. Grunwald, E., Proc. Int. Symp., Electrolytes, Trieste, 1959 (1962) 62. 13. Godneva, M. M., Klocho, Μ. Α., lzv. Karel'. Kol'sk. Fil. Akad. Nauk SSSR (1958) 5, 122. 14. Montgomery, D., et al., Proc. Okla. Acad. Sci. (1949) 30, 140. 15. Erva, J., Suom. Kemistil. (1956) 29B, 183. 16. Pinder, K. L., Can. J. Chem. Eng. (1965) 43(5), 271. 17. Ceausescu, D., Rev. Chim., Bucharest (1960) 11, 174. 18. "International Critical Tables," Vol. 4, p. 260, McGraw Hill, New York, 1926. 19. Abe, R., J. Tokyo Chem. Soc. (1911) 32, 980. 20. Shearman, R. W., J. Am. Chem. Soc. (1937) 59, 185. RECEIVED Feburary 6, 1978.


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