HETEROGENEOUS EQUILIBRIA 



239 



the freezing point method. The results obtained agree well with those 

 obtained by the freezing point method. 8 * 



2. The Molecular Weight of Electrolytes in Non-Aqueous Solutions. 

 A great many measurements have been made of the molecular weight of 

 electrolytes in various non- aqueous solvents. With a few exceptions, 

 the boiling point method has been employed. The resulting data suffer, 

 consequently, from the inaccuracies inherent in this method. Measure- 

 ments at low concentrations appear to be entirely lacking. In general, 

 in solvents of fairly high dielectric constant, where the ionization is com- 

 parable with that in water, the molecular weights as determined lie 

 below the normal values and indicate ionization. In solvents of fairly 

 low dielectric constant, usually below 20, the apparent molecular weight 

 rarely indicates ionization at higher concentrations. 



The most extensive molecular weight determinations in a non-aqueous 

 solvent have been made by Walden and Centnerszwer 9 with solutions in 

 sulphur dioxide. In Table LXXXIX are given values of the van't Hoff 

 factor i for various electrolytes dissolved in sulphur dioxide at dilutions 

 from 1 to 16 liters. An inspection of the table shows that, at a dilution 



TABLE LXXXIX. 



VALUES OP i FOR ELECTROLYTES DISSOLVED IN SULPHUR DIOXIDE. 



1. 



2. 



3. 



4. 



5. 



6. 



7. 



8. 



9. 

 10. 

 11. 

 12. 

 13. 

 14. 

 15. 

 16. 

 17. 

 18. 



KJ ..................... 0.42 



KCNS .................. 0.41 



NaJ ........................ 



NH 4 J ................... 0.41 



NH 4 CNS ................ 0.29 



RbJ .................... 0.52 



N(CH 3 )H 3 C1 ............ 0.28 



N(CH 3 ) 2 H 2 C1 ........... 0.87 



N(CH 3 ) 3 HC1 ............ 1.12 



N(CH 3 ) 4 C1 .............. 1.16 



N(CH 3 ) 4 Br .............. 1.30 



N(CH,) 4 J ............... 1.26 



N(C 2 H 5 )H S C1 ........... 0.43 



N(C 2 H 5 ) 2 H 2 C1 ........... 0.70 



N(C 2 H 5 ) 3 HC1 ........... 1.15 



N(C 2 H 5 )J .............. 1.61 



N(C 7 H 7 )H 3 C1 ........... 0.44 



S(CH 3 ) 3 J ............... 0.84 



0.55 

 0.49 

 0.57 

 0.53 

 0.40 

 0.61 

 0.38 

 0.79 

 1.00 

 1.08 

 1.10 

 1.20 

 0.50 

 0.69 

 1.06 

 1.39 

 0.51 

 0.97 



4 



0.63 

 0.60 



8 



0.74 

 0.68 



16 



0.86 

 0.71 



0.64 0.71 0.82 



According to Heuse (Thesis, Univ. of 111., 1914), the agreement between the con- 

 ductance and the vapor pressure method does not hold for KC1 at 25. . See also Wash- 

 burn, "Principles of Physical Chemistry," Ed. 2, p. 268. 



Walden and Centnerszwer, Ztschr. /. phys, Chem, 39, 513 (1902), 



