HENRYE. WIRTH,JOHN W. DROEGE AND JOHN H. WOOD
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mined the heat capacity of gelatin gels containing 0-91% H 2 0 by a drop calorimeter method. The molal heat capacity of the water present in a gel 25 containing 12.5% H20 as calculated from the data of Hampton and Mennie is given in curve 6, Fig. 2. Free water (water melting near 0") was not 20 present in gels containing less than 33% H,O. Curve 2, Fig. 2 gives the molal heat capacity of & 15 water as calculated from the heat capacities of the two samples of p-Nap. This curve resembles neither a typical hydrate curve nor the "bound" 10 water curve. The minimum at 140°K. is associated with the small anomaly in &NaP.0.010H20 and part, but not all of the maximum at 240°K. is 5 diie to the anomaly in the heat capacity of 6NaP.0.409H20. The most significant feature of curve 2 is that 0 the heat capacity corresponds to that of hydrate 100 150 200 250 300 water in the range 270-300°K. Temp. (OK.). Curve 1, Fig. 2, for the molal heat capacity of Fig. 2.-Molal heat capacity of water in: ( 1 ) €-Nap, [(CpNsP'0.716 H20 - cpNsP'O.482 HsO)/o.233] ; (2) P-Pu'aP, the water present in e-NaP is that expected for [ (CpNaP'O.409 H 2 0 - CpNaP'O. 010 H20)/0.399] ; ( 3 ) CdS04.8/3 adsorbed water. The heat capacity of the abH?O [(cpCdSO4'8/8 H20 - C p C d 8 0 4 * H 2 0 ) 3 / 5 1 ; (4) IC€' (5) CdSOd.Hz0 [CpCdSO~.EnO - C p c d s o r ] ; (6) in a gelatin gel sorbed water (270-300°K.) is greater than that of free mater. This is in agreement with the results containing 12.5y0HzO. of Hampton and Mennie" who found the average parallel that of ice and should permit conclusions specific heat of water to be as high as 1.24 in a gel to be drawn as to the nature of the binding of containing 54.7% H 2 0 even though this included the water between 0 and 12.5% H20which had an water with the substrate. In Fig. 2 the molal heat capacities are given in average specific heat of 0.80. Conclusions.-This work has verified the prethe range 90-300OK. for ice (curve 4), for the water vious conclusions that the first half mole of water present in GdSOl.H2O1O (curve 5), and for the additional water present in CdS04.8/3Hz010 per mole of NaP is strongly bound to the soap, (curve 3). The heat capacity of the hydrate and that any additional water is adsorbed on the water present in most of the hydrates reported in surface. The fact that t,he heat capacity of the the literature lies between curves 3 and 5. The water present in p-NaP lies within the range exonly values in the literature for the heat capacity of pected for hydrates in the temperature range "bound" water in the temperature range 90-300°K. 270-300°K. is strong evidence for the existence of a b.\. P"k are those of Hampton and Mennie" who deter- hydrate, NaP.1/2 H20. Acknowledgment.-The authors wish to express (8) K. K . Kelley and G. E. Moore, J . Am. Chen. SOC.,65, 2340 their sincere gratitude to Prof. Herrick L. Johnston (1943). (9) V. A. Koreev. Zhur. F i z . Khim., 22, 847 (1948). for his full cooperation in the use of facilities of the (10) M. N. Papadopouloa and W. F. Giauque, J . Am. Chsm. SOC.,77, Cryogenic Laboratory, and to the Procter and 2740 (1955). Gamble Go. for a fellowship which partially (11) W . F. Hnmpton a n d J. H. Mennie, Can. J . Research, 10, 452 supported this work. (1934). I
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HEAT CAPACITIES AND THERMODYNAMIC FUNCTIONS FOR 6- AND U-SODIUM PALMITATE BY HENRYE. WIRTH,JOHN W. DROEGE A N D JOHN H. WOOD Contribution from the cryogenic Laboratory and the Department of Chemistril, T h e Ohio Stnte University, Coliimbus, Ohio and f r o m the Department of Chemistry, Syracicse University, S p a c u s e , N . Y . Received A p r i l BS, 1058
The entropies of &sodium palmitate (Nap) (o.79yOHzO) and w-NaP (0.11% H,O) at 298.16'K. are 113.4 f 0.4 e.u. and 113.8 f 0.4 e.u., respectively. The entropies of completely anhydrous NaP a t 298.16OK. are estimated to be 112.2, 113.6 and 112.9 for the 6-,W - and ,?-phases, respectively.
Introduction The present work extends the study of the thermodynamic properties of palmitic acid and its derivatives's2 to the 6- and w-phases of sodium palmitate (Nap). (1) 11. E. Wirth, J, R. DroeeP
917 rl9-56),
nnd J. H. Wpod, THIS JOURNAL,60,
Experimental Materials.-A portion of the sample of w-NaP obtained in the course of the preparation of hydrous @-Nap*was used. The sample contained 0.08% H20 before and 0.14% H20 after the heat capacity determination, so was essentially anhydrous. (2) H, E, R'irth, J. IT.Wood and J. W. D F ~ P zbid., ~ P , 63, 149 (1959).
1Fj3 THERMODYNAMIC FUNCTIONS OF a- .4su U-SODIUM PALMITATE TABLE I HEATCAPA.CITIES (CAL./DEG. T . 'I
