346 Dr. Kohlrausch. The Resistance of the Ions [Feb. 17, 



of solid silver iodide, or those of W. Kohlrausch on its conductivity at 

 different temperatures, scarcely form a basis for conclusions in regard 

 to solutions in water, particularly as the behaviour of silver chloride 

 and silver bromide is quite different from that of silver iodide. 



In addition,' it is difficult to compare substances which are so highly 

 concentrated, in comparison with ordinary electrolytes, with dilute 

 solutions. All these conductivities reduced in the ratio of the con- 

 centration, as, for example, the measurements made on hot glass of 

 large surface and small thickness by means of the potentiometer, would 

 probably have to be considered zero, that is, smaller than the errors 

 of observation, in comparison with our dilute salt solutions at moderate 

 temperatures. 



Of the greatest interest for our problem are the recently published 

 measurements of electral conductivity as far as - 70° C, which Mr. 

 Kunz* was led to make through my remarks on the relation between 

 conductivity and temperature. He was unfortunately unable (as was 

 I also) to sufficiently over-cool dilute solutions, and the measurements 

 were therefore made on strong solutions of sulphuric acid of at least 

 4 gr. equiv./litre. Notwithstanding the fact that no certain conclu- 

 sions can be drawn in regard to dilute solutions, Mr. Kunz's values 

 are of sufficient interest to represent graphically. The curves are 

 marked with the percentage concentration of the solutions (fig. 2). 



Ftg. 2. 

















°lo 

















w 



My °w 































f 



/ 



































300 



-70° ~~ -60° -50° -40° -30° -20° -10° C O 



The conductivity of the strongest solutions sinks gradually with the 

 temperature, and reaches at - 70° a relatively small value. It is im- 

 possible to follow the more dilute solutions to so low a temperature on 

 account of their freezing. But it is evident from the observations that 

 the more dilute they are, the more rapid is the rate of change of the 



* ' Comptes Kendus,' vol. 135, 1902, p. 788. 



