Section 43, Change of Conductance with Temperature. 10/ 



It will be seen that silver nitrate has temperature-coefficients which run 

 parallel to those for potassium and sodium chlorides, and which, like the 

 lattef, pass through a maximum value somewhere in the neighborhood of 

 156. The coefficients of potassium sulphate and barium nitrate, on the 

 other hand, differ greatly from each other, and increase continuously with 

 rising temperature. 



With reference to the equivalent conductance values at the higher con- 

 centrations, mention need be made only of the fact that as shown in table 

 22, those for 80-milli-normal solutions have a maximum value at 281 in 

 the case of silver nitrate, at 218 in the cases of potassium sulphate and 

 barium nitrate, and at 100 in that of magnesium sulphate. This is, of 

 course, due to a compensation of the effect of increasing migration-velocity 

 by that of decreasing ionization. 



44. IONIZATION-VALUES AND THEIR CHANGE WITH THE 

 CONCENTRATION AND TEMPERATURE. 



In table 27 are given the ratios (multiplied by 100) of the conductances 

 at the various concentrations to that at zero concentration at each tempera- 

 ture. These ratios are at least an approximate measure of the percentage 

 ionization of the substances, in those cases where the hydrolysis is not 

 large and complex or intermediate ions are not formed, and provided the 

 conductances at zero concentration can be regarded as correct. It is not 

 probable that the hydrolysis is large enough at the higher concentrations 

 to seriously vitiate this interpretation of the results, except in the case of 

 magnesium sulphate at 100 and above. No definite information is avail- 

 able in regard to the existence at the higher temperatures of intermediate 

 ions like KS0 4 " and BaN0 3 + ; but the facts that transference determina- 

 tions* have shown their absence in any considerable quantity at ordinary 

 temperatures and that the functional relation between concentration and 

 conductivity is identical at all temperatures (as was shown in section 42) 

 make it probable that such ions do not exist in large quantity at the higher 

 temperatures. Aside from these uncertainties in the interpretation of the 

 conductivities at the higher concentrations, there is the possibility of con- 

 siderable inaccuracy in some of the values adopted for zero concentra- 

 tion. This possibility exists especially in the case of magnesium sul- 

 phate at 100 and above, for which the A values were derived from those 

 for potassium sulphate and barium nitrate under the assumption that the 

 magnesium and barium ions have equal migration-velocities. It may also 

 exist to some extent in the case of potassium sulphate and barium nitrate 



*See Noyes, Z. phys. Chem., 36, 79 (1901). 



