Liquid-Liquid Equilibria in Systern Benzene-Pyridine-Water J
d
JULI-AN C. SMITH, VICTOR D. STIBOLT’, AND ROGER W. DAY2 Cornel1 Cnicersify, Ithaca,
In
the solubility diagrams for a number of ternary liquid systems, the slope of the tie lines changes in direction as the amount of solute increases. Such systems have been called “solutropic.” Little is known of the effect of temperature on “solutropes”; this study established the effect of temperature, between 15” C. and the normal boiling point, on the solutropic system benzene-pyridine-water. This system is unusual even in relation to other solutropic systems. The variations with temperature of the limiting solubility curve and of the solutrope are unlike any previously reported, and none of the published correlations describes the equilibrium relations. Extensive study will be required before solubilities in such systems can be predicted accurately. A list of solutropic systems is included. Despite the solutropes, most of these systems can be used for extraction. Pyridine and water can readily be separated by extraction with benzene. Complete separation is not possible in “azeotropic” ternary liquid systems; the difference between c‘solntropic” and “azeotropic”systemsisi1lustrated.
.V. Y .
single investigator. Furthermore, recent data for the system benzene-pyridine-water (9) showed that the solutrope d i s a p pears a t the boiling point, even though it is marked a t room temperature (26, 33). This system was therefore studied a t temperatures from G oto 60” C., to establish the effect of temperature over a wide range. EXPERIMENTAL PROCEDURE
Thiophene-free reagent grade benzene and distilled water were used. One pound of Baker and Adamson purified pyridine was refluxed for 2 hours with 75 grams of potassium permanganate. It was then decanted into a distilling flask, 25 grams of additional potassium permanganate were added, and the pyridine was distilled through a short column filled with glass beads. The purified pyridine boiled between 113” and 114” C.; the lower boiling and higher boiling cuts were discarded.
TABLE1. SOLUTROPIC TERNARY LIQCIDSYSTEIISFOR J ~ ~ H I C H EXTENSIVE DATAh L E J A V A I L A B L E Temperature,
I
N MOST ternary liquid systems involving one partially mscible pair of liquids, the slope of the tie lines increases progressively as the amount of the third component rises. I n a number of systems, however, this is not true: Instead, the tie lines slope in one direction when the concentration of the third component is low, and in the opposite direction when it is high. The distribution ratio changes from less than 1 to more than 1; when it is unity the tie line is horizontal. This reversal of the direction of slope has been called a “solutrope,” and systems in which it occurs, “solutropic systems” (25). Ten years ago only a very few such systems were known, but they have now been shown to be fairly common. Data for eleven solutropic systems were recently summarized by Smith (66);a more extensive list is given in Table I. Essentially coniplete solubility diagrams are available for these systems. The solutrope occurs a t moderate to high concentrations of the third component, and, in general, disappears when the diagrams are plotted on a molar basis. Solutropes also occur in numerous systems with organic acids, listed in Table 11; these solutropes are evidenced by the variation in the distribution coefficients, and QCCW a t very low concentrations of the solute. These systems are solutropic on a molar basis; a few of them are solutropic on a weight basis also. This reversal of the slope of the tie lines, or solutrope, is superficially analogous to an azeotrope in a liquid-vapor equilibrium diagram, although, as is shown later, the analogy is not very good. Real “azeotropes” have been noted in ternary liquid systems (fl), but they are entirely different from solutropes. However, because many liquid-vapor azeotropes can be shifted or eliminated by changing the pressure and temperature, the effect of temperature on a typical solutrope became a matter of interest. Only a few of the systems listed in Table I were studied a t more than one temperature, and none of them very extensively by a
c.
Components
Citation
.4QUEOUS SVSTEhlS
Acetaldehyde-vinyl acetate Acetic acid Ethyl ether Isophorone Acetone Benzene Chlorobenzene Toluene Trichloroethylene Xylene Allyl alcohol-diallyl ether Aniline- aniline hydrochloride Benzene tert-Butyl alcohol Isopropyl alcohol Pyridine Pyridine teit-Butyl alcohol Benzene Ethyl acetate Ethyl ether dcetic acid Ethyl alcohol Ethyl alcohol Ethyl alcohol Isopropyl alcohol Benzene Cyclohexene Diisopropyl ether E t h y l acetate Toluene n-Propyl alcohol-cyclohexane Toluene Diethylaminea Isopropyl aloohol Trichloroethylene Acetone Acetonitrile Nicotine
20 25 24
22 25
(7) ($8)
25 0 , 20
23,35
25 25
(301
(32) ($9)
20 20 and b. pt. 17
NONAQUEOUS SYSTEMS
I Present address, E. I. d u Pont de Nemours & Co., Inc., Wilmington, Del. 2 Present addrees, Bird Machine Co , South Walpole, Mass.
Q
190
4cetone-glycol-benzene Diphenylhexane-furfural-docosane Double solutrope.
27 45, 8 0 . 115
(88)
(8)
January 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE11. SOLUTROPES INDICATED BY DISTRIBUTION COEFFICIENTS AT 25" C.
Page No. in Components
(8.8
AQUEOUS SYSTEM
a
Anisic acid-xylene Benzoic acid-petroleum ether a-Bromobutyric acid Benzene Chloroform Toluene Isobutyrio acid Benzene Carbon tetrachloride Chloroform Nitrobenzene Petroleum ether Toluene n-Butyric acid Benzene Carbon tetrachloride Chloroform Ni trobensene 0-Nitrotoluene Petroleum ether Toluene o-Chlorobenzoic arid-xylene Dichloroacetic acid-nitrobenzene 1.3,5-Dinitrobenzoic acid-xylene 0-Iodobenzoic acid-xylene Phenol-carbon tetrachloride Phenylacetic acid-xylene Picric acid-ethyl ethera Propionic acid Anilinea Chloroform Salicylic acid-xylene Trichloroacetic acid Ethyl bromide Ethyl ether Nitrobenzene o-Ni trotoluene n-Valeric acid Petroleum ether Toluene Xylene NONAQUEOUS SYSTEM8 Acetone-glycerol Ethyl amine Methylpiperidine
592 513 238 238 238
253 255 253 255 257 253 253-4 255 253 255 257 257 253, 256 476 78 472 478 386 583 330
JJ
sample was then reheated until the cloudiness disappeared, and was cooled once more. The critical solution temperature could thus be fixed to well within 0.5 C. A small amount of pyridine was then added, and the procedure was repeated. Curves similar to that in Figure 2 were obtained for a number of mixtures containing various ratios of benzene to water; by interpolation the limiting solubility curves a t each of several constant temperatures were constructed. The tie lines were established by titration of the pyridine in the conjugate layers. Known mixtures in the area of heterogeneity were carefully made up, shaken, and allowed to settle in a constant-temperature bath. Samples were then taken from each layer, weighed, and titrated with 1.5 N hydrochloric acid, using, a modified methyl orange indicator.
,THERMOMETER
192 187 524
69 68 69
lot30 Z JOINT
69
302 302 301
161 452
At 20' C.
ff
19E
The limiting solubility curve a t 15" C. was established by the cloud-point method described by Denzler (6). One branch was fixed by titrating 40-ml. samples of known pyridine-water mixtures with benzene to the first permanent turbidity. A known quantity of pyridine wm then added, and the titration with benzene was repeated. The other branch of the curve was determined by titrating known benzene-pyridine mixtures with water. During the titrations all samples were held in a constanttemperature bath. At temperatures above 25' C. the cloud-point method did not work well because of evaporation of the benzene and pyridine. The limiting curves were therefore established from the critical solution temperatures of known mixtures. Measured volumes of pyridine, benzene, and water, to give a total volume of about 35 ml., were mixed in a glass-stoppered 125-ml. Erlenmeyer flask. Five milliliters of the known mixture were pipetted into a small test tube carrying a female ground-glass joint, into which an Anschiitz thermometer, lubricated with silicone stopcock grease, was tightly fitted. The test tube was immersed in a beaker of water a t a temperature somewhat above the expected critical solution temperature, and was shaken vigorously while being heated. After the two liquid phases coalesced into a single homogeneous liquid, the test tube was cooled in the air and shaken. When the first trace of cloudiness became visible, the temperature was noted. The
Figure 1. Constant-Temperature Separatory Funnel
In the measurements a t 15' C. the samples were made up i n glass-stoppered Erlenmeyer flasks, which were then immersed in a large constant-temperature bath. Samples of each layer, of about 15 ml. each, were removed wihh a pipet for analysis. A t elevated temperatures this method was unsatisfactory because of evaporation of the organic liquids; a closed constant-temperature separatory funnel was therefore used. It was much: simpler and easier to make than the separator recently described by Smith and Bonner ( 2 7 ) , and proved entirely satisfactory. It consisted of a vertical glass cylinder, 6 inches high and 1 inch in diameter, fitted with a 14/35 female ground-glass fitting a t the top, and a 10/30 female fitting a t the bottom. A 4-inch length of IO-mm. glass tubing extended from the lower ground fitting through the bottom of a glass jacket. The jacket was 2.25 inches in diameter and 12 inches high; it carried an overflow of 10-mm. glass tubing just below the level of the top of the inner cylinder. The bottom outlet of the inner chamber was plugged with a tapered ground-glass plug on the end of a glass rod, 5 nim. in diameter and 11.5 inches long. A sealed cap of 12-mm. glass tubing, 6 inches long and carrying a male 14/35 ground' fitting, fitted over the top of the glass rod and closed the inner chamber. The ground joints were lubricated with silicone stopcock grease. This apparatus is shown in Figure 1. In making a determination, known mixtures in the area OK heterogeneity were placed in the inner chamber and thoroughJy
INDUSTRIAL AND ENGINEERING CHEMISTRY
192
ea 70
ORIGINAL MIXTURE PYRIDINE 5 3 % BENZENE 2 0 %
DEGREES C.
WATER
27%
Vol. 43, No. 1
as the temperature rises; in the systems ethyl alcohol-ethyl ether-water, n-propyl alcohol-cyclohexane-water, isopropyl alcohol-ethyl acetate-water, and lertbutyl alcohol-ethyl acetatewater, the peak rises slightly. In the system benzene-pyridinewater, as shown in Table V, the peak of the curve falls and then rises once more.
l
60
PYRlOl NE
5C
e GILLIN (9 0 SMITHGA! 4c
I
I
60
62
3P 20
SO 4
50
52
54
56
58
Figure 2. Critical Solution Temperatures of BenzenePyridine-Water Mixtures near Peak of Limiting Solubility Curve
shaken. The cap yvas set in place, and hot water from a large beaker was passed through the jacket. The temperature of the water in the jacket was measured by a thermometer. Because the inlet and outlet water lines were rubber tubing, the entire apparatus could be shaken as the mixtures were heated. The agitation could not be very vigorous, but with even mild agitation the two layers quickly came to equilibrium a t the elevated temperatures. The samples were held a t the desired temperature for about half an hour, or until each layer became completely clear. The cap was then removed, and a small sample of the lower layer was allowed to run into a tared ice-cold Erlenmeyer flask, which was quickly stoppered and replaced in an ice bath. The rest of the lower layer, and some of the upper layer, were drained and discarded; any liquid adhering to the inside of the drain tube was removed with a small cloth. A sample of the upper layer was then collected in a second cold Erlenmeyer. After thorough cooling, the two samples were weighed and titrated with standard hydrochloric acid. LIMITING SOLUBILITY CURVES
Figure 3.
Solubility Diagram at 15' C.
In two solutropic systems, as in most normal ternary liquid systems, the mea of heterogeneity in the solubility diagram diminishes considerably as the temperature is increased. In the system acetonitrile-trichloroethylene-water the peak of the curve falls from 69% t,o about 54% acetonitrile as the temperature rises from 20' C. to the normal boiling point; in the nonaqueous system diphenylhexane-docosane-furfural the mea of heterogeneity, large a t 45" C., disappears a t a temperature slightly above 140" C. EQUILIBRIUM DlSTRIBUTION
Data for the tie lines a t various temperatures are given in Table 117; the solubility diagrams for 15", 45", and 60' C. are Figures 3 to 5. In all three diagrams the direction of the slope of the tie lines changes as the concentrat.ion of pyridine rises, but a t the higher temperatures the horizontal tie line approaches the peak of the limiting solubility curve. ,4t the boiling point there is no solutrope.
Data for the limiting solubility curves a t 15", 45", and 60" C., and a t the normal boiling point, are given in Table 111. As the temperature rises the curve a t the benzene side of the diagram moves inward; a t the center it moves downward until the temperature reaches about 50" C., and then rises again. Thus the peak of the curve becomes sharp as the boiling point is approached. TABLE 111. LIMITINQSOLUBILITY CURVES In a rather nariow range of concentrations, the 60° C. Boiling Point (9) 15' C. 450 c. ternary mixtures have two critical solution temPyridine, Water; Pyridine, Water, Pyridine, Water, Pyridine, Water, wt. % wt. % wt. % wt. % wt. % wt. % wt. % wt. 75 peratures, -4s shown in Figure 2 , some mixtures 23.5 1.7 1.7 34.2 1.3 form two liquid layers up to about 45" C.; in 3.6 2.6 3.1 36.7 42.3 6.4 6.4 5.6 44.3 48.7 the range between 45" and 65" C. they are 8.9 7.4 51.2 8.5 49.2 homogeneous; above 65" C. they separate into 11.8 10.7 11.3 51.8 52.1 13.0 14.1 13.6 63.4 53.3 two liquid layers once more. This type of be17.8 17.9 16.2 54.1 56.8 24.9 19.8 19.3 54.4 57.4 havior of the limiting solubility curve in ternary 29.8 22.7 22.7 54.4 58.2 liquid mixtures has not previously been reported. 33.9 29.6 29.7 53.6 58.4 38.1 34.0 34.1 52.4 57.6 In seven of the nine solutropic systems which 50.2 42.9 42.7 48.6 54.7 66.7 55.3 55.6 40.1 51.7 have been studied Ict various temperatures, the 72.9 73.4 25.0 52.4 limiting solubility curve is not greatly affected 48.2 44.6 by temperature changes. In the systems iso39.0 27.1 propyl alcohol-cyclohexene-water and acebonebenzene-water the peak of the curve falls slightly
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1951
DISTRIBUTION DATA
TABLEIV.
Wt. % Pyridine a t lba C. Benzene layer Water layer 16.4 7.5 27.7 24.1 31.8 36.4 35.8 46.8 37.9 53.3 44 8 57.3
At 60" C. 12.5 26.2 20.5 36.1 30.1 39.3 37.2 41.9 44.4 44.6 47.8 46.8 52.2 48.9
*
Wt. % Pyridine at 46O C. Bencene layer Water layer 20.9 8.4 33.8 20.7 37.4 32.0 39.2 39.9 41.6 46.8 43.9 51.4 46.4 63.7
At Boiling Point ( 8 ) Benzene layer Water layer 5.5 18.7 7.1 23.9 10.9 31.3 16.6 37.2 23.2 43.8 29.6 51 . O 58.2 41.5
' C. 70.8 72.0 73.3 74.7 76.2 77.8 79.3
To show the relative position of the horizontal tie line in the diagram, the ratio of the percentage of pyridine in the solutrope to that a t the peak of the limiting curve is given in Table V, and plotted against the temperature in Figure 6. The graph is somewhat curved, and indicates that the solutrope disappears a t about 75" C. At low temperatures the plait point is on the left-hand side of the diagram; about 75" 0.it is a t the peak of the limiting curve; a t higher temperatures i t shifts to the right-hand side of the diagram.
TABLEV. Tpp.,
C. 15 25 ($6,93) 45 60 7 9 . 3 (0)
EFFECT OF TEMPERATURE ON SOLUTROPE Wt % Pyridine Atpeakof In aolutrope, P1 limiting curve, 29.8 68.6 56.3 34.8 39.1 64.4 54.45 45.0 55.2
Ps
...
50.9 61.8 71.9 82.6
...
In no other system has this shift of the plait point from one side of the diagram to the other been observed, although it would almost certainly occur in the system trichloroethylene-nicotinewater. Figure 6 shows the effect of temperature on four solutropic systems.
PYRIDINE
I n the system ethyl alcohol-ethyl ether-water the horizontal tie line is almost at the top of the diagram a t 0" C. and below, and sinks as the temperature is raised. I n the systems isopropyl alcohol-cyolohexene-water and n-propyl alcohol-cyclohexanewater the horizontal line also sinks as the temperature rises. T h e sketchy data available for these systems indicate that the horizontal tie line would reaoh the bottom of the diagram, and the solutrope disappear, a t about 70" or 80" C . The systems isopropyl alcohol-ethyl acetate-water and tert-butyl alcohol-thy1 acetatewater are slightly solutropic a t 0" C., but not a t 20" C.; the horizontal tie line sinks t o the base of the diagram a t an intermediate temperature. When the solutrope disappears in this manner the plait point does not shift from one side of the diagram to the other. I n the system diphenylhexane-docosane-furfural the horizontal tie line rises as the temperature is raised, a t least between 45" and 80" C.; the data for higher temperatures are too incomplete to show the behavior. I n the system acetonitriletrichloroethylene-water the horizontal tie line also rises with temperature, as in the system benzene-pyridine-water, but the rise is slow. At the boiling point in the acetonitrile system the solutrope still exists, and the plait point has not shifted from one side of the diagram to the other.
As mentioned before, solutropes are only superficially analogous to azeotropes in liquid-vapor equilibrium diagrams. When the ternary diagrams for the solutropic systems listed in Table I are plotted on a molar basis, the solutrope disappears: all the tie lines slope in one direction. Regardless of the method of plotting, the solvent is selective over the entire range of concentrationsfor example, despite the strongly marked solutrope, benzene can effectively be used to separate any mixture of pyridine and water by extraction. True azeotropes have recently been noted in ternary liquid solubility diagrams (6), but they are entirely different from solutropes. The selectivity of a solvent is best indicated by the ratio of the concentration of solute in one layer, on a solventrfree basis, to the corresponding concentration in the other layer. In the system benzene-pyridine-water, i t is the ratio of pyridine to water in the benzene layer, divided by the ratio of pyridine to water in the water layer. For a solvent to be truly nonselective, the concentrations of solute on a solvent-free basis in the two layers must be equal. This means that the tie line corresponding to such an azeotrope, when extended, passes through the point representing the pure solvent. This is true whether the diagram is plotted on a weight basis or on a molar basis. The difference between a solutrope and an azeotrope is illustrated by Figure 7 . If the mixture of solute and water represented by point S in the solutropic system is extracted with the solvent, the conjugate layers are separated, and the solvent is
PYRIDINE
10A 9 0
A
a
Figure 4. Solubility Diagram at 45" C.
193
Figure 5. Solubility Diagram at 60" C.
194
INDUSTRIAL AND ENGINEERING CHEMISTRY
1.0
Vol. 43, No. 1
Thus the system benzene-pyridine-water is unusual, even in xelation to the comparatively few other known solutropic systems. The area of heterogeneity diminishes and then increases as the teinperature is raised; the horizontal tie line rises toward the t o p of the solubility curve, and reaches the peak a t a temperature slightly below the boiling point. The plait point migrates from one side of the diagram to the other. Lastly, none of the coirelations proposed for ternaiy liquid svstems correctly describes the equilibrium distribution relationships.
0.9
0.8 0.7
0.6 05 BlLlTY CURVE
0.4
ACKNOW L E D G M E K T
0.3
The authors are indebted to 8.W. Francis, &cony-Tracuum. Oil Co., for pointing out many of the solutropic s y s t e m for which data are available.
0.2 0.1
LITERATURE C l T E D
'-30
-20 -10
Figure 6.
0
IO 20
30
40
50
60
70 80
90 100
Effect of Temperature on Solutropes
distilled out of them, the resulting mixtures of solute and watrr will be different. I n the azeotropic system mixture A cannot be separated into different fractions by extraction with the solvent, because the ratio of solute to water in both conjugate layers is the same. An example of an azeotropic ternary system is teit-amyl alcohol-glycerol-watr a t 48.6" C. (6). Such azeotropes cannot exist, or a t least are exceedingly unlikely, when the mutual solubility of the partially miscible liquids is very small. In systems of this kind the limiting curve is very near the sides of the triangle when the solute concentration is low; a tie line passing through the point representing the solvent would have to be almost impo&bly steep. I n the benzene-pyridine-water system, the selectivity of the solvent, benzene, is 50 or more when the pyridine concentration is small, and decreases to 5 or 6 a t pyridine concentrations of about 45 yo. The benzene necessarily becomes nonselective a t the plait point, but a t all other points it is strongly selective for pyridine. I t s selectivity diminishes steadily as the temperature rises, but is still large a t 60" C. and above. SOLUTE
A
SOLUTE
A
(1) Beech, D. G., and Glasstone, S., J . Che?n. S o c . ( L o n d o i i ) , 1938,
67. (2) Bonner, W. D., J.P h y s . Cliem., 14, 738 (1910). (3) Brigys, S.W., and Comings, E. W., IND.ENG.CHEM.,35, 411 (1943). (4) Corliss, H. P., J . Phys. Chem., 18, 681 (1914). (5) Denzler, C. G., Ibid., 49, 358 (1945). (6) Elgin, J. C. (to Colgate-Palmolive-Peet Co.), U. S. Patent 2,479,041 (Aug. 16, 1949). ( 7 ) Fairburn, A. IF'., Cheney, H. A., and Cherniavsky, .4. J., Chem. Eng. P r o g w s s , 43, 280 (1947). (8) Frere, F. J., IND. ENG.CHEM., 41,2365 (1949). (9) Gillin, J., Jr., "Vapor-Liquid Equilibria for t,he Syatem BenzenePyridine-Water," Ph.D. thesis, Cornel1 University, Julie 1949. (10) Hand, D. B., J.Phvs. Chert., 34, 1961 (1930). (11) Horiba, S., Mem. Coll. Eng. K'yoto I m p . Unic., 3, 63 (1911). (12) Kono, M., J. Chem. Soc. Japan, 44, 406 (1923). (13) Lalande, A., J. cltim. phys., 31, 583 (1934). (14) Major, C. J., and Swenson, 0. J., IND.ENG. CHELi., 38, 834 (1946). (15) Miller, W. L., and NcPherson, R. H., J . P h p . Chem., 12, 706 (1908). (16) Olsen, A. L., and Washbui,n, E. R., J . Am. C'hem. Sor., 57, 303 (1935). (17) Othmer, D. F., and Tobias, 1'. E , , INI. ENG.C k E x r . , 34, 693 (1942). (18) Othmer, D. E'., White, R. E., and Trueger, E., Ibid.,33, 1240, 1513 (1941). (19) Pratt, €1. 13. c., Trans. Inst. C h n . E-ngrd. (Lnndorz), 25, 43 (1947). ( 2 0 ) Pratt, H. R. C . , and Glover, S.T.. Ibid.,24, 54 (1946). (21) Redly, .T.. Kelly, D. F., and O'Connor, A I , , J . Chenz. S o c . (Loizdon), 1941,275. (22) Seidell, A , "Solubilities of Organic Compounds," 3rd c d . , S e w Pork, D. Van Nostrand Co., 1940. (23) Sidgwick, S . V., Pickford, P., and Wilsdon, R. H., J. CLfm. Soc. (London), 99, 1122 (1911).
SOUTROPIC
PZEOTROPIC
Figure 7 . Solutropic and Azeotropic Ternary Systems
For the usual type of ternary system, in which the slope of the tie lines increases progressively, several methods of correlating the equilibrium distribution are more or less generally applicable. None of them holds for the system benzene-pyridine-water. The correlation proposed by Hand (IO) defines the distribution a t the boiling point, and a t lower temperatures when the pyridine concentration is very small; a t higher concentrations of pyridine i t fails, as does the relation of Othmer and Tobias (17). I n many solutropic s y s t e m the distribution coefficient is constant, provided the degree of molecular association of the solute in the two layers is properly considered ( 8 5 ) ; in the system benzenepyridine-water this is not true.
(24) Simonsen, D. R., and Washburn, E. R., J . A m . C'lie~n.S n c . , 68, 235 (1946). ( 2 5 ) Smith, A. S., 1x0. ENG. CHEM.,42, 1206 (1950). (26) Smith, J. C., J . Phys. Chem., 46, 376 (1942). (27) Smit,h, T. E., and Bonner, R. F., IND.ESG. CHEW,42, 896 (1950). (28) Trimble, H. M.,and Fraser, G. E., Ibid.,21, 1063 (1929). (29) Washburn, E. R., and Beguin, A. E., J. Am. Chem. S O C . , 62, 579 (1940). (30) Washburn, E. R., Brookway, C. E.. Graham, C. L., and Deming, P., Ibid.,64, 1886 (1942). (31) Washburn, E. R., Graham, C. L., Arnold, G. B., and Trailsue, L. F., Ibid.,62, 1454 (1940). (32) Wehn, M. E., and Franke, K. IT., IKD.ENG.CHEM.,41, 2SS3 (1949). (33) Woodman, R. M., and Corbet, li. S., S. Chem. SOC. ( L o n d o n ) , 127,2461 (1925). RECEIVED June 29,1950.
