240 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



of 16 liters, a few salts have a value of i greater than unity, while the 

 greater proportion of the salts has a value of i less than unity. At 

 higher concentrations the curves exhibit a very complex form. In the 

 case of most of the substances which have a relatively high value of i at 

 lower concentrations, the value changes but little until a concentration 

 of 0.2 normal is reached, when the value of i begins to increase rapidly 

 with increasing concentration. In the case of salts having a low value of 

 i at the lower concentrations, the value of i, in general, decreases with 

 increasing concentration, particularly as normal concentration is ap- 

 proached. Certain of the electrolytes exhibit an exceptional behavior 

 in that the curves of the i values intersect those of the majority of the 

 electrolytes. It is evident that molecular weight determinations in sul- 

 phur dioxide are uncertain in their significance. On the whole, the curves 

 exhibit a definite trend as the concentration decreases indicating that the 

 value of i will ultimately rise above unity. It is to be borne in mind 

 that the ionization of salts in sulphur dioxide is relatively low, being in 

 general less than 20 per cent in the neighborhood of 0.1 normal. Further- 

 more, even in the case of aqueous solutions, freezing point and con- 

 ductance methods lead to divergent results at higher concentrations. If 

 the divergence of a solution of an electrolyte from the simple laws of 

 dilute solutions is in any considerable measure due to the electrostatic 

 action of the charged particles upon one another or upon the solvent me- 

 dium, then it is to be expected that as the dielectric constant of the sol- 

 vent is smaller, the divergence at a given concentration will be greater, 

 since the force due to a charged particle varies inversely as the dielectric 

 constant. It seems not improbable, also, that, in the case of certain sol- 

 vents, polymerization may take place to a considerable extent at higher 

 concentrations. This would greatly complicate the behavior of these solu- 

 tions and would make it impossible to interpret either the results of 

 conductance or of osmotic measurements. 



The molecular weights of a number of electrolytes in liquid ammonia 

 at its boiling point have been determined by Franklin and Kraus 10 from 

 the boiling point measurements. Owing to the exceptionally low value 

 of the boiling point constant of liquid ammonia, about 3.4, measurements 

 below 0.1 normal were not made. As a consequence, the determinations 

 relate almost entirely to concentrations at which it might be expected that 

 the laws of dilute solutions would not hold. In general, in the neighbor- 

 hood of 0.1 normal, the observed elevation of the boiling point corre- 

 sponds approximately with a normal value of the molecular weight of 

 the dissolved electrolyte. At higher concentrations, the molecular eleva- 



Franklin and Kraus, Am. Chem. J. 20, 836 (1898). 



