Thermochemistry of nonaqueous electrolyte solutions

Heats of solution and specific heats have been measured for NaI and KI in methanol at 25 and 50 for the full range of concentrations; the integral heat of solution of NaI or KI in methanol has a positive temperature coefficient, whereas the heats of solution of these salts and all strong electrolytes in water have negative temperature coefficients. The thermal capacity of an aqueous electrolyte is less than the sum of the thermal capacities of the components, whereas the result for methanol is the reverse. In addition, the integral heat of solution has a concentration coefficient much larger than that found for water, mainly because water has a dielectric constant about 2.5 times that of methanol. This leads to stronger interactions between ions in methanol, which contains ion pairs.