242 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



While the correspondence between the two methods is not very exact, 

 nevertheless it is evident that the relations in these solvents are similar 

 to those found in aqueous solutions. 



In pyridine the values of i are in general less than unity, as may be 

 seen from the following table. 



TABLE XCI. 



VALUES OF i FOR SOLUTIONS IN PYRIDINE. 

 AgN0 3 (C 2 H 5 ) 4 NI 



V= 128 7= 16 32 



i 0.77 0.75 0.91 i 0.73 0.82 



The molecular weight of sodium iodide in acetone has been deter- 

 mined by McBain and Coleman. 12 The values obtained are very nearly 

 normal from 0.9 to 0.04 normal concentrations. If anything, the mole- 

 cular weights are slightly larger at the lower concentrations. At these 

 concentrations, the conductance method indicates an ionization varying 

 from 17 to 43 per cent. It is evident that in this solvent the results of 

 conductance and of osmotic measurements are not in agreement. In 

 acetone, however, the deviations from the law of simple mass-action are 

 large, and there is evidence that polymerization of the dissolved salts 

 takes place, presumably with the formation of complex ions. 12a This 

 renders the interpretation of results in the more concentrated solutions 

 difficult. 



Phenol is the only non-aqueous solvent in which the molecular weights 

 of salts have been determined at relatively low concentration. Riesen- 

 feld, 13 from the freezing point of a saturated solution of potassium iodide 

 in phenol, whose concentration is 0.0045 normal, obtained a value of 170, 

 for the molecular weight of potassium iodide, which corresponds closely 

 with the normal value of 166. The equivalent conductance of solutions 

 of potassium iodide in phenol at these concentrations is of the order of 

 1.0. Hartung 14 has measured the molecular weights of a number of 

 salts in phenol by the freezing point method. These include tetramethyl- 

 ammonium iodide, sodium acetate, aniline hydrochloride, dimethylamine 

 hydrochloride, as well as several organic salts of alkali metals. The 

 concentrations run to dilutions, in some cases, as low as 0.01 normal. In 

 the following table are given the values obtained for i for solutions of 

 tetramethylammonium iodide and sodium acetate in phenol. With 

 aniline hydrochloride, i has a value of unity at a concentration of 0.02 N 



"McBain and Coleman, Trans. Faraday Soc. 15. 45 (1919). 

 "Serkov, Ztschr. f. phys. Chem. 78, 567 (1910). 

 Riesenfeld, Ztschr. /. phys. Chem. 41. 346 (1902). 

 "Hartung, Ztschr. /. phys. Chem. 77, 82 (1911). 



