COMMUNICATIONS TO THE EDITOR
2759
mated from the relation of Ito, Ono, and Yarna~hita.’~ The polymers were hydrolyzed in water a t 60” for 24 hr. Titrations were performed in the absence of salt on aliquots containing 50 mg of polymer in 50 ml of water with 0.19 N NaOH, using a Radiometer Model 25 pH meter with glass and calomel electrodes. The hypercoiling phenomenon of the butyl copolymer a t low charge is essentially identical with the behavior previously found for highly charged poly~oaps.’~-’~ It is not difficult to predict that as we increase the alkyl chain length of the maleic acid-alkyl vinyl ether copolymers, the compact form will be increasingly stabilized and the transition to the random coil form correspondingly displaced to higher values of a. That the dodecyl copolymer behaves as a typical polysoap when cr = 1 has already been dernon~trated.’~A comprehensive study of such polyelectrolyte to polysoap transitions as a function of alkyl chain length, degree of ionization, added electrolyte, and temperature is in progress.
The yoreported by Shafrin and Zisman should be compared with the nonequilibrium yoof Johnson and Dettre (Figure 2 in ref 2) which is 20.7 dynes/cm a t 24 5”. If we assume a temperature correction of 0.4 dyne/cm, yo a t 20” would be about 21.1 dynes/cm, which is in better agreement with Shafrin and Zisman. The data of Aveyard and Haydon (Figure 1 in ref 1) (which also do not include adsorption from the vapor) give a yo of about 21.3 dynes/cm.
Acknowledgment. This work was supported by Grant GM-12307 from the National Institutes of Health, United States Public Health Service.
Concentrated Electrolyte Solution Transport
(1) E. G. Shafrin and W. A. Zisman, J . Phys. Chem., 71, 1309 (1967). (2) R. E. Johnson, Jr., and R. H. Dettre, J. Colloid Interface Sci., 21, 610 (1966).
E. I. DU PONTDE NEMOURS & COMPANY, INC. WILMINGTON, DELAWARE19898
R. E. JOHNSON, JR. R. 11. DETTRE
RECEIVED APRIL26, 1967
Theory : Directly Measured Glass Temperatures and Vitreous Ice
(14) K. Ito, H. Ono, and Y. Yamashita, J . Colloid Sci., 19, 28 (1964). (15) U. P. Strauss and E. G. Jackson, J . Polymer Sci., 6 , 649 (1951). (16) U. P. Strauss and N. L. Gershfeld, J . Phys. Chem., 58, 747 (1954). (17) U. P. Strauss and B. L. Williams, ibid., 65, 1390 (1961).
Sir: I n recent articles,’J the longstanding problem of interpreting the isothermal transport behavior of electrolyte solutions a t high concentrations has been discussed in terms of the dilution of the high concentration SCHOOLOF CHEMISTRY PAULDUBIN limiting “solution” which, in the case of ambient temRUTGERS, THESTATEUNIVERSITY ULRICH P. STRAUSS perature solutions of salts of multivalent ions, is asNEWBRUNSWICK, NEWJERSEY 08903 serted to be an ideal glassn3 The approach is thus the reverse of the traditional development which takes the RECEIVED APRIL24, 1967 infinitely dilute solution as starting point. Since a central feature of the approach is the thermodynamic significance attached to the ideal glass transition, a Comments on “Critical Surface Tension for matter which presents conceptual difficulties and is still controversial, some direct experimental support for the Spreading on a Liquid Substrate,” by approach is desirable to establish its plausibility. E. G. Shafrin and W. A. Zisman To provide such support we present here some independent measurements which bear out predictions of Sir: Shafrin and Zisman’ report the critical surface the transport model and a t the same time relate the tension of water (as measured with n-alkanes) as 21.7 basis of the concentrated solutions treatment to the dynes/cm. They state (on p 1314) that “Johnson and properties of pure water. Dettre’s significantly lower value of yo = 19.1 dynes/cm The interpretation of the concentration dependence a t 24.5” is difficult to explain since one would not expect of conductance‘ has been based on the explanation of the 4.5” temperature difference to cause such a change the temperature dependence of the process, the equain yo.” We would like to point out that the two yc)s do not (1) C. A. Angell, J . Phvs. Chem., 7 0 , 3988 (1966). refer to the same system. Johnson and Dettre’s2 (2) C. A. Angell, J . Chem. Phys., in press. value refers to systems in complete equilibrium. ( 3 ) An “ideal glass” is defined as a glass from which the configurational entropy content characteristic of the liquid state has comShafrin and Zisman’s value refers to systems not in pletely vanished; i.e., there is no “frozen in” entropy. See, e.g., adsorption equilibrium with the vapors of the alkanes. J. H. Gibbs and E. A. Dimarsio, J . Chem. Phys., 2 8 , 373 (1958). Volume 71, Number 8 July 1967
