166 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



of the ions. At the higher temperature the force which drives the ion is 

 greater, and the fluidity of the medium through which the ion moves would 

 be greater. Both of these factors increase the velocity of the ions and, con- 

 sequently, increase the conductivity as the temperature is raised. Jones calls 

 attention to the fact that the mass of the ion decreases with rise in temperature. 

 He does not refer to the charged atom or group of atoms which are usually 

 termed the ion, but to this charged nucleus plus a larger or smaller number of 

 molecules of water, which are attached to it and which it drags along with it 

 in its motion through the remainder of the solvent. 



At the higher temperature the hydrate formed by the ion is less complex 

 than at a lower temperature. The less the number of molecules of water 

 combined with the ion, the smaller the mass of the ion and the less its resist- 

 ance when moving through the solvent. Therefore, the ion will move faster 

 at the higher temperature, and the conductivity of the solution will increase 

 with rise in temperature. 



Jones also points out the fact that, at the higher dilutions, the temperature 

 coefficient of conductivity for any given substance is greater than at the lower 

 dilutions. The hydrate at the higher dilution is more complex than at the 

 lower. This being so, the change in the composition of the hydrate with 

 change in temperature would be greater at the higher dilution and, conse- 

 quently, the temperature coefficient of conductivity is greater the more dilute 

 the solution. 



After this brief review of the most important facts which have been found 

 concerning the effect of temperature on conductivity, let us study the tempera- 

 ture coefficients which we obtained. 



In a previous paper 1 we have pointed out the presence of solvates in non- 

 aqueous solutions, not only in the case of lithium bromide, but also for several 

 other electrolytes. That there is a combination of the solvent with the dis- 

 solved substance to form solvates is now a generally accepted fact. 



In the pure solvents, with but one exception, the temperature coefficients 

 of conductivity are greater at the higher dilutions than at the lower. This 

 may be explained by the fact that if the solvate at the higher dilution is 

 more complex than at the lower, then the change in the composition of the 

 solvate in question, with change in temperature, is greater at the higher 

 dilution. Consequently, the more dilute the solution the larger the temper- 

 ature coefficient of conductivity. 



In the mixtures of the solvents we found that, in practically every case, 

 there was an increase in the temperature coefficients with increase in dilu- 

 tion. There is combination of the solvent and dissolved substance to form 

 a solvate, and we believe the explanation is the same as that given above. 



1 Amer. Chem. Journ., 35, 316 (1906). 



