GUNNAR0. ASSARSSON
1436
Ute in dimethyl sulfoxide are relatively less than those of the same solute in the other solvents. Acknowledgment.-The authors of this paper wish to express their appreciation to the Stepan
Vol. 60
Chemical Company for donating the dimethyl sulfoxide and to the U. S. Army Signal Corps for the use of several items of equipment in the performance of this research.
EQUILIBRIA I N THE TERNARY SYSTEM MgClt-BaC12-H20 BETWEEN 18 AND 100' BYGUNNAR0. ASSARSSON Chemical Laboratory of thc Geological Survey of Sweden, Stockholm 60, Sweden Received M a y 68,1965
The ternary system MgClTBaClrHzO was examined within the temperature range l&lOOo. There occur three phases of barium chloride: dihydrate, monoh drate and anhydrous salt. The solubility of barium chloride in saturated magnesium chloride solutions is insignificant. $hue, it is possible to determine the lowest formation temperature of barium chloride monohydrate only as being < 45". The lowest formation temperature of anhydrous barium chloride is a t 83 f 3". The formation of the phases was confirmed by X-ray exposure in a heating camera. Two isotherms, 50 and loo", and a synoptic diagram of the ternary system are given.
I n some earlier papers,' we have published the results of investigations concerning the equilibria in some of the aqueous systems of alkaline earth and alkali chlorides. T o complete the survey, knowledge is required of the systems containing these chlorides and barium chloride. Also the chlorides of Li, Cs and Rb could be taken into consideration in the final summing up of the results, but the systems containing these chlorides are believed t o have been studied elsewhere.2 The results from the investigation of barium chloride together with magnesium chloride will now be presented. Experimental The experiments were performed a6 earlier described. Magnesium and barium were separated and determined gravimetrically using the same method as for magnesium and strontium.' The Barium Chloride Hydrates Occurring in the System. -The earlier known Dhases of the barium chloride are the dihydrate, the monoh9drate and the anhydrous salt. Barium chloride dihydrate has been investigated by Tovborg-Jensen.* It is monoclinic, belonging to the space group P21/n, and its lattice parameters are a = 7.136, b = 10.86, c = 6.738 A., = 90'57'. Barium chloride monohydrate was first described by Skey and Davis4 as tetragonal, and later by Kirschners as orthorhombic. Skey and Davis' preparation was obtained from a barium chloride solution containing hydrochloric acid, Kirschner's preparation from nearly pure methyl alcohol. Experiments performed in connection with the present investigation showed that these two preparations do not have identical X-ray patterns. The preparation obtained by Kirschner's method contains methyl alcohol. Later Pinskere determined the structure of the compound using the electron diffraction method and found the monohydrate to be orthorhombic, having the unit cell dimensions a = 4.51, b = 9.02, c = 11.28 A. The monohydrate is usually prepared by dehydration of the dihydrate between 45 and 60". For identification of the monohydrate in the equilibrium studies described below, (1) G. 0. Assarsson and A. Bdder, Tms JOURNAL, 66,416 (1954) and literature there cited. (2) Cf. Y. Y. Dodonov, L. V. Eferova and V. 8. Kolosova, Doklady Akad. Nauk S.S.S.R.,63, 301 (1948); V. E. Plyushchev and N. F. Markovskaya, J . Obshchei Rhim., 24, 1302 (1954) and other Russian authors. (3) A. Tovborg-Jensen, K g l . Danske Vidsnskaps Selskab. Mat. jus. Meddel., 22, No. 3 (1945) (English). (4) W. Skey and E. H. Davis, Trans. New Zealand Inst., 3 , 220 (1870).
(5) A. Kirschner. Z . phydk. Chem., 1 6 , 176 (1911). (6) G. Pinsker, Zhum. Fix. Kliim., 23, 1058 (1949).
X-ray photographs of analytically controlled preparations of this kind (55"), were compared with those of.preparations obtained at 70-80' by diffusion of solutions containing hydrochloric acid (20-30%) into a barium chloride solution. The X-ray patterns of these latter preparations were shown to be identical with those of the monohydrate prepared by dehydration a t 55". The measurements were in very good agreement with those listed in the card catalog of A.S.T.M.' On comparison with values obtained by calculations based on Pinsker 's unit cell dimensions the agreement between observed and calculated d-values and intensities was generally tolerable. It should be kept in mind that the monohydrate may be rather easily dehydrated during bombardments of the electrons under the low pressure conditions of an electron diffraction apparatus. Anhydrous barium chloride has been examined by DO11 and Klemm* who have calculated its orthorhombic cell dimensions per analogia a = 7.823, b = 9.33, c = 4.948 A. The anhydrous barium chloride can easily be prepared by dehydration ofothe hydrates in a thermostat a t temperatures higher than 80 . Preparations of this kind (100') were used for comparison of the X-ray patterns of the phases in the equilibrium experiments described below; the measurements of the diffractions were in very good agreement with those given by Doll and Klemm. A hemihydrate of barium chloride seems also to exist, being formed on cautious dehydration of the dihydrate a t 70-85". However, as it is metastable it has not been observed among the phases of the aqueous systems.
Results The solids in equilibrium with solutions of the system include no double salt within the temperature range investigated. The principal interest is therefore connected with the changes in the isothermally invariant equilibria and the lowest formation temperature of the hydrates of barium chloride. As the saturated magnesium chloride solutions have a dehydrating effect on barium chloride dihydrate, barium chloride monohydrate and anhydrous barium chloride must be formed a t temperatures which are low compared with the corresponding ones in the pure aqueous system (102' for the monohydrate, 268" for the anhydrous saltg). I n an accurate determination of the lowest formation temperature of the phases some difficulties were encountered. The experiments were (7) Alphab. and numer. index of X-ray diffraction data A.S.T.M. Spec. Techn. Publ. No. 48 B, 1950. (8) W. Dall and W. Klemm, Z . ano~g.allgem. Chem., 241,248 (1939). (9) G. I. Hattig and Chr. Slonim, Z. anorg. allgem. Ch., 161, 66 (1929): A. Benrath, ibid., 241, 147 (1941).
c
1437
EQUILIBRIA IN THE TERNARY SYSTEM MGCL~-BACLZHIO
Oct., 1956
/
V Fig. 1.-The
ternary system MgCIZ-BaCI2-H20: the isotherm a t 50'.
TABLE I THESYSTEM MgClz-BaClrHzO EXPERIMENTS FOR REACHI N G EQUILIBRIA C L O S E T O T H E ISOTHERMALLY INVARIANT POINTS Symbols: Ba 2 = BaC1~2H20,Ba 1 = BaClrHZO, Ba = BaC12; Mg 6 = MgC126HzO; X = controlled with X-ray photographs. T%mp.. Compd. C. added 25.0 Ba Bal Ba2 36.0 Ba 1 Ba2 42.0 Bal Ba2 45.0 Bal Ba2 47.0 Bal Bs2 70.0 Ba2 Ba2 Bsl Be2 81.0 Ba Bal Ba2 83.0 Ba Bal Ba2 85.0 Ba Bal
BaGh
50
f l 4
Soln. MgCh BaClz 35.7 .05 .05 35.7 .05 35.7 36.4 .05 .05 36.4 .05 36.9 .Q5 36.9 .05 37.0 .05 37.0 .05 37.2 .05 37.2 35.2 .2 30.5 .4 29.6 .5 26.2 1.1 39.8 .I5 39.8 .I5 39.8 .15 39.9 .I5 39.9 .15 39.9 .I5 40.0 .15 .I5 40.0
Wet residue MgCla BaCla 19.8 45.6 B a l 14.1 56.3 6.9 69.8 8.2 70.0 7.0 70.3 6.2 74.1 75.8 4.2 17.1 54.6 10.9 64.3 10.3 67.1 6.5 75.8 11.1 64.6 7.1 72.7 5.4 72.3 4.6 72.9 16.8 55.5 04.0 12.6 59.5 14.8 19.6 49.0 64.4 12.2 10.4 69.0 61.6 15.2 12.2 68.8
Phase formed BaX Bal Ba2 Ba 1 Ba2 Bal Be2 BalX BalX BalX BalX Bal Bal Ba2 Ba2 BalX Ba 1 Bal BaX BalX Bel Ba Ba
+
25 and 36': equilibrium not reached
performed by saturating the solutions with magnesium and barium chloride, filtering off the undissolved solids, and afterwards adding a small
amount of barium chloride. The analyses of the solids formed showed, however, that they were dependent upon the type of hydrate of barium chloride which was added. At 25' up to about 40' the solid contained dihydrate when dihydrate was added, and monohydrate and anhydrous salt when the solid added was the monohydrate and/or anhydrous salt. The results were similar even when tho samples were shaken in the thermostat for a day, for a week or for longer time. Thus, equilibrium could not be reached. At first, when the temperature was about 45' or higher, there did occur a rather complete transformation of the dihydrate into the monohydrate. Some of these analyses are listed in Table I. It seems to be impossible to reach equilibrium for these reactions within a reasonable time, obviously because of the insignificant solubility of barium chloride in the saturated magnesium chloride solutions which produces a coating of hydrated salt round the grains of the salt added. As a real equilibrium cannot be reached in practice, the lowest formation temperature of barium chloride monohydrate cannot be determined; it can only be concluded that it is somewhat below 45". When the solutions are not concentrated, the transformation of the unstable into the stable phase is performed more easily, as shown by the isotherm a t 50" (Table 11, Fig. I). For the same reason the transition temperature of monohydrate-anhydrous barium chloride is not determined
GUNNAR0. ASSARSSON
1438
Vol. 60
B o GI,
50
Fig. 2.-The
ternary system MgClzBaClz-HzO:
the isotherm at 100".
more exactly than 83 f 3'. The more dilute TABLE I1 solutions of the 70" isotherm, partly given in THETERNARY SYSTEMMgC12-BaC12-H20 ISOTHERMS AT Table I, and of the 100" isotherm in Table 11, 50 AND 100" show the formation of the stable phases. I n Temp., s01n. Wet residue OC. MgCln BaCh MgClr BaCln Phase" order t o confirm the results, some X-ray photo50 37.4 ... ... ... Mg6 graphs were taken in a high temperature camera. 36.9 0.05 ... ... Bal+MgB A sample of barium chloride dihydrate was ground 36.7 0.05 11.6 04.0 Ba 1 34.1 0.15 9.1 68.4 Ba 1 X together with 10% magnesium chloride hexahy32.5 0.20 5.1 73.8 Ba2 X drate under water-free mineral oil. The oil was 26.8 0.40 3.5 75.0 Ba2 removed by pressing the sample between filter 20.7 2.30 2.0 78.8 Ba2 ... ... Ba2 12.2 10.60 ... 30.4 ... ... B a 2 100 42.2 ... ... ... M g 6 '
40.9 37.6 31.5 24.0 18.4 18.9 12.7 11.3 9.9 4.2 2.4
...
0.2 0.2 0.9 2.9 8.0 14.0 15.7 17.7 20.2 29.7 33.2 37.3
9.8 9.6 5.1 7.7 7.3 2.2 1.7 1.8 2.4 0.6
0.8
...
74.6 72.8 81.3 73.3 65.1 84.0 85.8 72.2 78.0 80.0 81.2
...
Ba Ba Ba Ba Ba Ba Ba Bal X Ba 1 X Bal Ba 1 Ba2
Symbols see Table I.
Fig. 3.-The ternary system MgClt-BaC12-HZO: synopsis on the isothermally invariant equilibria.
paper; the sample, now consisting of very minute crystals, was packed into capillaries of Lindemann glass which were then fixed into the heating camera. The temperature of the camera could only be regulated rather approximatively, and the temperatures used for these experiments were 25-30', 50-55' and 100-105". The X-ray photographs showed in the first case dihydrate, in the second case mono-
POTASSIUM ALKANE TRICARBOXYLATES
Oct., 1956
hydrate and in the third case anhydrous salt of the barium chloride, in very good agreement with those photographs obtained from the corresponding pure compounds.
i439
The main outlines of the present system are given in Fig. 3 which with some assumptions for the highest and the lowest temperatures gives a survey of the formation of the solids.
THE CRITICAL MICELLE CONCENTRATIONS IN AQUEOUS SOLUTIONS OF POTASSIUM ALKANE TRICARBOXYLATES BYKozo SHINODA~ Department of Physical Chemistry, Faculty of Engineering, Yokohama National University, Minamiku, Yokohama, Japan Received May 88, 1066
The critical micelle concentrations (CMC) in aqueous solutions of paraffin chain salts which possess three carboxyl groups at one end of their hydrocarbon chain have been determined. The CMC values are determined as 0.79 mole/l. for R&H(COOK)CH(COOK)t, 0.095 mole/l. .for RtaCH(COOK)CH(COOK)2and 0.012 mole/l. for RIICH(COOK)CH( COOK)Za t 25’. The relation between the logarithm of the CMC of above substances and the number of carbon atoms in hydrocarbon chain is linear and the slope of the line is 0.52. From the comparison of CMC values of paraffin chain salts which possess one, two or three carboxyl groups at one end of their hydrocarbon chain, the electrical and cohesive energies per micelle forming ion have been determined. These values agree with the theoretical values.
Introduction The critical micelle concentrations (CMC) in aqueous solution of paraffin chain salts which possess two carboxyl groups at one end of their hydrocarbon chain have been reported in the preceding paper.2sa As a result i t has been found that (1) a homologous series of potassium alkyl 15 times higher CMC malonates shows 3.5 values compared with that of corresponding fatty acid salts, (2) the plot of the logarithm of CMC versus the number of carbon atoms in hydrocarbon chain, m, is linear and (3) the logarithm of CMC as a function of the logarithm of the concentration of counterions is also linear and the slope of the line is just twice that of fatty acid salts. It also has been verified for the first time that the slope of the plot of log CMC versus m is not constant but varies with the number and kinds of polar groups concerned. Consequently, it has become important and interesting to study the surfactants which possess three dissociable groups a t one end of their hydrocarbon chain to gain further information on the mechanism of the micelle formation and on the action of surfactant^.^ The present investigation has been undertaken to measure the CMC in aqueous solutions of a series of potassium 1,1,2-alkanetricarboxylates,RiCH(COOK)CH(COOK)2, and to determine the electrical energy and cohesive energy at the micelle formation from the comparison of the CMC values of potassium alkane mono-, di- and tricarboxylates. Experimental
-
“Nihon Yushi” purest grade fatty acids were used a8 starting materials. These fatty acids showed sharp and exact melting points. The or-bromo fatty acid was obtained by the bromination of fatty acid with bromine in the presence of a small amount of phosphorus trichloride, and
. (1) Department
of Chemistry, University of California, Berkeley,
California. (2) K. Shinoda, THIBJOURNAL, 69,432 (1955). (3) The CMC values of osmotic pressure measurements by Brahama D. Sharma, et al., show good agreement. (4) The properties of the monolayer of alkane di- and tricarboxylic acids were reported in H. Hatta and T. Iseniura, Bull. Chem. SOC. J a p a n , a9, 90 (1956).
purified by vacuum distillation. The or-bromo fatty acid ethyl ester was obtained by esterification of or-bromo fatty acid with ethyl alcohol, and purified by vacuum distillation. Alkane 1,1,2-tricarboxylic ester was synthesized by the addition of sodiomalonic ester to a-bromo fatty acid ethyl ester. Then alkane l,l,2-tricarboxylic ester was saponified with alkali in alcohol and then acidified to alkane 1,1,2tricarboxylic acid. The final purification of octane, dodecane and hexadecane 1,1,2-tricarboxylic acids were carried by the recrystallization from water, 1:1 acetic acid-water solution and glacial acetic acid, respectively, and their melting points were 129, 135.5 and 135’. The determination of the CMC has been performed by the initial change in color of pinacyanole in dilution process of concentrated s o l u t i ~ n . ~ - ~
Results and Discussions . The CMC values obtained are 0.79 mole/l. for RsCH(COOK)CH(COOK)2,0.095 mole/l. for RiaCH(COOK)CH(COOK)z and 0.012’ mole/l. for RllCH(COOK)CH(COOK)za t 25’. The relation between the logarithms of the CMC of the homologous 1,1,2-alkanetricarboxylatesand the number of carbon atoms in the hydrocarbon chain, m, fits the equation log CMC = - K 4 m
+ Const.
(1)
where K4 is an experimental constant given as 0.52. The CMC values obtained by the interpolation are 0.28 mole/l. for RsCH(COOK)CH(COOK)2 and 0.034 mole/l. for RlzCH(COOK)CH(COOK)2. A linearity of the log CMC versus m had been noted previously for several homologous series of paraffin chain electrolytes.8-ll As a result of a series of potassium alkyl malonates,2 it has been found that the slope of the log CMC versus m changes with the number of polar groups concerned. The present investigation of the homologous series of potassium alkane tricarboxylates also offers the evidence that the slope ( 5 ) M. L. Corrin and W. D. Harkins, J . Am. Chem. Soc., 69, 079 (1947). (6) K. Shinoda, THISJOURNAL, 58, 541 (1954). (7) P. Mukerjee and K. J. Mysels, J . Am. Chem. Soc., 77, 2937 (1955). (8) J. Stauff, 2. physilc. Chem., A183, 55 (1939). (9) G.S. Hartley, Kolloid Z.,88,22 (1939). (10) K. Hess, W. Philippoff and H. Riessig, ibid., 88,40 (1939). (11) A. B. Scott and H. V. Tartar, J . Am. Chem. Soc., 66, 692 (1943).
