SOLUTIONS AS A FUNCTION OF TEMPERATURE 161 



temperature of 10. As the concentration of the solution increases, 

 the maximum is shifted toward lower temperatures as indicated by the 

 dotted curve. At 0.01 normal the maximum lies in the neighborhood of 

 30, while at 0.031 normal the maximum is still further displaced in 

 the same direction. At 0.1 normal the maximum remains at practically 

 the same value, but at 0.31 normal the maximum is displaced toward 

 higher temperatures, being very flat in this case and lying somewhere 

 in the neighborhood of 10. At 1 normal the maximum has arisen to 

 temperatures above + 10 and the conductance increases markedly over 

 the entire temperature range from 50 to + 10 The maximum 

 occurs at the lowest temperature at a concentration in the neighborhood 

 of 0.1 N. These curves represent, in general, the behavior of solutions 

 at different temperatures. They correspond very closely with the values 

 obtained by Franklin 14 for solutions of KI in S0 2 . The maximum in 

 the conductance-temperature curves shifts from higher to lower tem- 

 peratures with increasing concentrations, reaches a minimum, and there- 

 after again shifts from lower to higher temperatures with increasing con- 

 centration. In certain cases the effect of viscosity is such that it just 

 counterbalances the effect of increased ionization over a considerable 

 temperature interval. Ammonium sulphocyanate dissolved in sulphur 

 dioxide is an example of this type, the conductance being practically 

 independent of temperature at a concentration of approximately 0.1 

 normal. At concentrations greater than 0.1 normal the temperature 

 coefficient of ammonium sulphocyanate solutions in sulphur dioxide is 

 positive and is the greater the greater the concentration of the solution, 

 while at lower concentrations the temperature coefficient is negative and 

 initially increases with decreasing concentration. Ultimately, however, 

 the sign of the coefficient must change. The fact that solutions in all 

 solvents, without exception, exhibit maxima in the conductance-tempera- 

 ture curves at intermediate concentrations indicates that at the tem- 

 peratures in question the constant m has reached a value near or 

 greater than unity. Curves of this type have been observed in solu- 

 tions in ammonia, sulphur dioxide, water, methyl and ethyl amine, and 

 methyl and ethyl alcohols. It is not to be doubted that the phenomenon 

 is a general one. That the temperature coefficient of solutions becomes 

 positive at very high concentrations is indicated by practically all data 

 available for solutions at high concentrations. In general, it has been 

 found that the higher the concentration the greater the value of the tem- 

 perature coefficient, or rather that the temperature coefficient passes 

 through a minimum or negative value at intermediate concentrations. 



" Franklin, loc. cit. 



