576
COMMUNICATION TO THE EDITOR
An interpretation of the thermodynamic data is that the quasi-ice-like structures caused by the dissolution of ethylene in water are more rigid or penetrate to a greater distance from the ethylene molecule than those created in diethyl sulfate and other non-polar compounds. Presumably this is due to the hydrogen bonding in water. Furthermore, the type of structure in the non-polar compounds is quite stable as the temperature changes; the thermodynamic functions for the compounds listed in Table I1 have essentially constant values over the temperature range for which data are available. The arrangement of the structure surrounding the ethylene molecule in diethyl sulfate appea:rs to be independent of the nature of the solvent for both diethyl sulfate and those compounds listed in Table 11. (6) J. Horiuti, Bull. Insf. Phys. Chem. Research (Tokyo), 9, 697 (1930); Sei. Papers Inst. Phys. Chem. fiesearch (Tokyo), 17,125 (1931).
Vol. 65
TABLE I1 PARTIAL MOLALHEATSA N D ENTROPIES OF SOLUTION FOR ETHYLENE DISSOLVED IN NON-POLAR SOLVENTS~ (0 TO 40') - PLO- ZG), - (ISL - QG), caI./ Solvent
cA./g. moleb
(g.
mole)('K.)
c
2420 16.5 CCll CHaCOOCH3 2260 16.5 2220 16.2 CaHa (CHahCO 2130 16.1 Standard State: Calculated from data of reference 6. "infinite dilution." Standard State: mole fraction = 1.o.
0
Acknowledgment.-This research was supported by a grant from the Petroleum Research Fund administered by the American Chemical Society. Grateful acknowledgment is hereby made to the donors of this fund.
COMMUNICATION TO THE EDITOR SPECIFIC REFRACTIVE INCREMENT OF POLYPROPYLENE I N a-CHLORONAPHTHBLEKE Sir: We have determined the specific refractive increment for solutions of isotactic polypropylene in a-chloronaphthalene a t 125". Our weighted average value it3 dn/dc 7 -0.189 0.005 cc./g. for mercury green (5460 A.) light. The measurements were made using a differential refractometer of the Debye' design as modified by Schulz.2 The instrument was calibrated with aqueous solutions of potassium chloride using the data of Stamm.8 The value obtained is consistent, as expected, with measured values of dn/dc for the system polyethylene-a-~hloronaphthalene.~-~ It is also in good agreement with that reported by Chiang,7 -0.188 cc./g. a t 140". (Chiang's value becomes -0.191 cc./g. a t 125" using a temperature coefficient equal to that for the polyethylene-a-chloronaphthalene system, approximately $0.0002 cc./ g. "C.) However, our results do not support the value of -0.216 cc./g. a t 145" reported by Parrinis (which becomes - 0.220 cc./g. when similarly corrected
*
(1) P. P. Debye, J . Applied Phys., I T , 392 (1940). (2) G V. Schula, 0. Bodmann and H.-J. Cantow, J . Polymer Sei.. 1 0 , 7 3 (1953). (3) R F. Starnm, J . Opt. Soc. A m . , 40, 788 (1950). (4) F. W. Billmeyer, Jr., J . A m Chem. Soc., 76, 6118 (1953). ( 5 ) R. Chiang, J . Polymer Sca., 36, 91 (1959). (6) V. Kokle, .'I W. Billmeyer, Jr., L. T. Muus and E. J. Newitt. presented a t the 139th National Meeting of the American Chemical Society, St. Louis, Mo., April 23, 1961. (7) R. Chiang, J. Polymsr Sci., 28, 235 (1958). (8) P. Parrini, F. Sebastiano and G. Messina, Makromol. Chem.. 38, 27 (19601.
to 125') or the value of -0.227 cc./g. at 125" reported by Kinsinger and Hughes.9 Although Parrini's value was measured directly, that of Kinsinger and Hughes was obtained from an extrapolation to 125' of values measured at 25" and 50", and mas supported by calculations based on the Gladstone-Dale relationship which, as the authors noted, is highly unlikely to be applicable to hydrocarbon polymer-a-chloronaphthalene systems. Kinsinger'O also used a value of 1.532 for the refractive index of a-chloronaphthalene a t 125". The correct value for this quantity for mercury green light is 1.594 i 0.0002, as measured several times in our laboratory over the past decade, and supported by calculation from the data of Auwers and Fruhling. Until the apparent discrepancy is resolved between values of dnldc reported by ourselves and Chiang and those reported by Parrini and Kinsinger, it would appear advisable to apply with caution the viscosity-molecular weight relations published for the system polypropylene-a-chloronaphthalene.7-9J2 POLYCIIEMICALS DEPARTMENT N. E. WESTON E. I. DU PONT DE NEMOURS A N D Co., Isc. D u PONT EXPERIMENTAL STATION WILMINGTON 98, DELAWARE F. W. BILLMEYER, JR. RECEIVED DECEMBER 6, 1960 (9) J. B. Kinsinger and R. E. Hughes, J. Chem. P h y s . , 6 3 , 2002
(1959).
(10) J. B. Kinsinger, Ph.D. Thesis, University of Pennsylvania, 1958. (11) K. V. Auwers and A. Frilhling, Liebig'8 Ann., 422. 192 (1921), reproduced in part in the "International Critical Tables," Vol. VII, p. 49. (12) S. Shyluk, paper presented a t the 138th National Meeting of the tlinerican Chemical Society, New York, N. Y., September, 1960.
