930
RAY C. CHASDLER .IKD JAMES W. RICBAIS
(14) KASAGY, J.: Unpuhlished data. (15) LASGXIR,I.: J. i2m. Chem. SOC.40, 1361 (1918). (16) l\ICB.41S, J. IC., GOOD,S.J., BAKR,A . nr., DAVIES, D. P., WILLAVORP,A . J., ASD BUCKISGHAM, R . : Trans. Faraday Soc. 29, part 2, 1086 (1933). (17) ORR,W.J. C.: Trans. Faradny SOC.40, 320 (1944). (18) P A ~ L I SLG. :, J. Am. Chem. Soc. 67, 555 (1945). (19) PICKETT, G.: J . Am. Chem. SOC.67, 195s (1945). (20) ROVES,J. V,, A N D BLAINS,R. L.: I d . E n g . Chem. 39, 1659 (1947). (21) SHAW, T . AI.: J . Chem. Phys. 12, 391 (1944). (221 SIMNA, R., .4sn ROWEX,,J, W.:J. A m Chem. SOC.70, 1663 (1948). ( 2 3 ) SwAsaras, T . B . : J. Textile Inst. 27, Tl95 (1936). (211 VRQL-HART, d.R . : J. Testile Inst. 16, T569 (1924). ( 2 5 ) WHITE,H. J., . ~ N DEYRING, H.: Textile Research J. 17, 10, 523 (1947).
DIFFI-SIOS *4SD OSAIOTIC COEFFICIESTS, COSDUCTIT'ITY, 3'IEIfBR-ISE XSXLYSES, AIXDTHE D E T E R P f I S h T I O S O F ?tlICELL.ilI CH-IRGE d X D CORIPOSITIOS I S SOME COLLOIDXL ELECTROLYTES' RAY C. CHANDLERz AND JAMES W. McBAIS Department of Chemistry, Stanford University, California Received September 18, 1948 IKTRODTCTIOK
The properties of colloidal electrolytes have been determined most successfully when the concepts have been hutijected to numerous independent physical meayurements. McBain and collaborators have utilized conductivity (9), dew point (19), density (G), dye numhers (14, 21), diffusion (13, 17), electromotive force i l l ) , freezing poirit (10, 12, lo), solubilization (14), surface tension (71, transport number ( 3 ) , ultrafiltration (13), ultracentrifugation (18), vapor tension (4), and x-ray studies ( 2 ) in their contributions to the subject. The general problem that initiated this investigation n-as the study of typical colloidal electrolytes with special consideration of their free diffusion and diffusion through membranes. The program included diffusion, conductivity, and freezing-point determinations as basic data. I n preliminary work on membranes it was discovered by one of us (R.C.C.) that the osmotic response of charged porous membranes to the valence of ions in solution offered a ne\v and useful technique for the evaluation of the charge on micelles. The experimental Tvork developed three major approaches: (a)determination of diffusion coefficients as basic data, ( b ) osmotic and conductivity data as a 1 Presented a t the Twenty-first National Colloid Symposium, which xas held under the auspices of the Division of Colloid Chemistry of the American Chemical Society at Palo Alto, California, June 18-20, 1947. Present address Depzrtment of Chemistry, Chico State College, Chico, California.
COLLOIDAL ELECTROLYTES
931
neasure of particle number and quality, (e) membrane analyses of particles rith respect to charge and composition. The data from these studies are cor.elated to determine micellar charge and composition. MATERIALS
Materials of the highest purity obtainable were tested and four cationic coloidal electrolytes were chosen whose titration and conductivity data assured heir suitability. These materials were laurylpyridinium chloride, myristylrimethylammonium chloride, cetyldimethylbenzylammonium chloride, and etyltrimethylammonium bromide. hereafter to be referred to as LPC, MTX%C, :DILIBAC, and CTMXB, respectively. METHODS
Physical Digusion: Integral diffusion coefficients were determined using the doublended Sorthrup-McBain type of diffusion cell as described by McBain and lawson (13), allowing approximately 10 per cent diffusion of 0.10 IIf solutions cross the glass membrane. Solutions and cells were freed of gases and the exleriment was begun after steady state within the membrane had been attained. Conductivity: Conductivity measurements were carried out using a Research Jodel Jones-Dyke type alternating current bridge, determining the null point y means of an oscilloscope. Stock solutions were prepared with conductivity rater having a specific conductivity of 7 X lo-’ ohm-’ cm.-l The concentraion was adjusted after titration and appropriate dilutions in Pyres flasks. Samles were introduced into the conductivity cell by reduced pressure, and conducvity water blanks were treated exactly like the solutions. Osmotic coefiients: Osmotic coefficients are based on freezing-point data for ilutions of approximately 0.05 M , 0.10 111, and 0.20 M concentration where ilubility permitted. One of us (R.C.C.) observed that when the freezingoint data were plotted versus concentration the points fell in a straight line hich intersected the ideal freezing-point lowering (FPL) curve a t a point which lay be called the idealized critical concentration. This simple geometrical :lationship enables one to determine any freezing point or other colligative roperty where the data fall in the straight line, as, for example:
+ b(c - d ) a + b(c - d )
FPL = u
’
(1)
1.858,~ here a is the FPL at the ideal critical concentration, b is the slope of the straight le, c is the concentration of the colloidal electrolyte, d is the ideal critical conntration, y is the osmotic coefficient, and n is the number of ions per molecule infinite dilution. This relationship applies t o many, and perhaps all, colloidal xtrolytes over the range through n-hich a rapid decline of g-values occurs. I t s mneral application t o representative colloidal electrolytes is illustrated in the plotted data shown in figure 1. =
932
R h P C . CHAKDLER BND JAMES W. hICBAIS
As a consequence of this relationship all colligative data may be calculated within this range when tIvo points are established. X fair degree of accuracy may he obtained when one point has been determined and the critical concentration is known. For the cetyl compounds (CDMBAC and CTMAB), which are too insoluble for freezing-point determinations, one point each determined by Dr. M. N.Fineman (4) by means of the thermoelectric vapor-tension method plus the critical concentrations derived from our conductivity data enabled us to construct all points desired for their g curves (figure 4). 1.0-
-
.9
/
/Bp
9 .5- 4’I
-nc
.5:.
/
,
Aerosol
t Z O .
d
AY
0.5
1.0
conc.
01
.5.7u
2
;;// K
caprate 0.5
Cone.
.02-
/
.om-
‘‘18”
.OM
I.
1
’d
I8
-
8r
.3
,’
Aerosol
MA
.014-
, T l e r o s o , OT
.I-
,012
,
,,
,
.
,
. .
I
,
FIG.1. Plot of freezing-point depression US. concentration. D a t a of McBain and Bolduan (replotted) : J. Phys. Chem. 47, 94 (1943).
Chemical The concentrations of the detergents, all of which had halide anions, were determined using silver nitrate with potassium dichromate as indicator, as was also done for the determination of potassium chloride and calcium chloride solutions. Cerium chloride solutions \\-ere titrated using silver nitrate and dichlorofluorescein indicator.
Membrane analyses Membranes were prepared from pyroxylin (cellulose nitrate) as described by Sollner ( 2 3 ) , Sollnrr, *-ibrams, and Carr (24), Abrams and Sollner (l),Sollner and Gregor (25), and Carr, Johnson, and Kolthoff (3). Two types of charged membranes are employed for distinctly different purposes. The first of these i: the charged porous permeable membrane which exhibits anomalous osmosis in the presence of dilute solutions of ions. Such a membrane sharply differentiate: the valence of ions of the same charge as that of the membrane by its osmotic
COLLOIDSL ELECTROLYTICS
933
response. To the authors’ knoJvledge, this technique has not been used previously to determine the valence or charge on ions or particles. It is used here t o estimate the charge on micelles when the molar concentration and osmotic. coefficient of the experimental solution are known. The osmotic transfer of water across the membrane increases markedly with valence. Rag type membranes approximately 25 I 80 mm. were mounted on short glass tubes that terminated in 2 mm. capillaries 80 em. long. Each membrane has its own characteristics. The rate of osmotic flow is dominated by the valence of the ion of the same sign as that of the membrane, concentration having a relatively minor effect. The molar concentration (c) and the osmotic coefficient (9) of the cxprrimental solution must be knonn in order t o prepare standard ion solutions for the determination of charge. The solutions to he discuwd are all cationic detergents, hence the valence of the cation alone is considered. It may readily bc bhonn that the concentration of micelles i i proportional to cg. Monovalent micelles formed from the experimental solution are comparable t o cg coiiccnt ration of monovalent ions: divalent micelles t o $cq caonwntration of tlivalent ion%; trivalent micelles to +cq concentration of trir-dent ion in a variety of concentrations of tivo of these colloidal electrotes. Comparison of conductivity and osmotic coefficients s h o m that the intrinsic nductirity of the micelles formed just above the critical concentration changes 3idly with concentration.
944
J O E L ?I. HILDCURASD
REFEREXCES (1) SBRAJIS, I., . ~ K DSOLLSER, IC.: J. Gen. Physiol. 26,369 (1943). (2) BOLDUAN, 0 . E . A., A~CBAIN, J. W.,AND Itoss, S.:J. Phys. Chem. 47, 528 (19-23). (3) C.4RR, c. JOHSSOS, 'w. I?., AXD KOLTHOFF, I. &I.: J . Phys. Colloid Chem. 51, 636 (1947). (4) FINEXAN, M. K., A N D MCBAIN,J. W.: J. Phys. Colloid Chem. 52, 881 (1948). (5) LAIAG, M. E.: J . Phys. Chem. 28, 673 (1924). (6) MCBAIS, &I. E . L., DYE,W. B., - 4 s ~JOHNSOS,S. A . J. 4 m . Chem. Soc. 61, 3210 (1939). ( 7 ) M c B a r ~ AI. , E . L., A N D PERRY, L. IT.: J . Am. Chem SOC. 62, 989 (1940). (8) hIcBa~x,J. W.:J. Am. Chem. Soc. 50, 1636 (1928). (9) MCBAIS,J. W., AND BETZ,AI. D.: J . .4m.Chem. SOC. 57, 1905 (1935). (10) AICBAIN,J. W., A N D BCTZ,M. D.: J. Am. Cheni. SOC.57, 1909 (1935). (11) M c B ~ I s ,J. W., AXD BETZ,AI. D.: J. .4m. Chem. Soc. 57, 1913 (1935). (12) AICBAIN,J. W.A N D BOLDUAN, 0. E. A . : J. Phys. Cheni. 47, 94 (1943). (13) MCBAIS,J. W., A N D Dawsos, C. R.: J. Am. Chem. Soc. 56, 52 (1934). (14) MCBAIN,J. W., AND GREEN,SISTERAGNESAss: J. Am. Chem. SOC.68, 1731 (1946). (15) XCBAIN,J. W.ASD JESKINS, K.J . . J . Chem. Soc. 121,2325 (1922). (16) MCBAIN,J. W.,LAISG,31.E A N D TIILCY, I?. . J. Chem. SOC.115, 1279 (1919). (17) MCBAIN,J. W.,.4ND LIU,T. H : ,J. . ~ I I I . Chem. SOC.63, 59 (1931). (18) XCBAIS,J. W.,A N D O ' S ~ L L I V AC. Y ,11..J . Am. Chem. Soc. 57, 2631 (1935). C. S.:J. Ani. Cheni. Soc. 42, 426 (1920). (19) RICBAIN,J. W., ASD SALVON, (20) ~ I C B A I N J. ,W., A N D WILLIAMS, R. C.: J. -4m.Chem. Soc. 55, 2250 (1933). (21) MCBAIS,J. W.,AND Woo, T. : J. Am. Chem. Soc. 60, 223 (1938). (22) MICHAELIS, L.: J. Gen. Physiol. 8, 33 (1926). (23) SOLLNER, K.: J. Phys. Chem. 49, 47 (1945). (24) SOLLNER, K., ABRAMS, I., AND CARR,c. J . Gen. Physiol. 24, 467 (1921). (25) SOLLSER, K., AND GREGOR, H. P.: J. Phys. Chem. 50, 53 (1916).
w.,
w.:
SETEX L I Q U D PHASES IS EQULIBRIUM JOEL H. HILDEBRAND
Department of C h em i s t r y, U n i ver s i t y of Cal i f orni a, Berkeley, California Received J a n u a r y 3, 1949
Some years ago I gave an address (2) at Irhich I prujected a photograph of a system of five liquid phases in stable equilibrium-mercurZ., phosphorus, x-stter, aniline, and hesane-the record at that time, so far as I am an-are. Subsequent!y ( 3 ) a sixth phase, liquid gnllium, \vas added. The recent development of the chemistry of fluorocarbons and the application t o them of solubility theory now makes it possible to add a sewnth phase. -1. photograph of the resulting system is here reproduced in figure 1, TI here the phase3 are labeled. It may be of interest to reviejv briefly the several factors responsible for the coexistence of so many liquid phases. The strong hydrogen bonding explains the water pha-e. &hilineis soincn-hat soluble in water by virtue of the hydrogenbonding amino group, hut only t o :i limited extent hecause of the clifficnlty of
