SOLUTIONS AS A FUNCTION OF TEMPERATURE 



145 



temperature rises, the temperature coefficient decreases. The conductance 

 curve is therefore concave toward the axis of temperatures. If the tem- 

 perature is carried sufficiently high, the conductance passes through a 

 maximum after which it decreases, the negative temperature coefficient 

 increasing as the temperature rises. Experiments of this kind were first 

 carried out by Sack, 1 who found that, in solutions of copper sulphate, 



-60 ' 



O 2O 46 % 6O 6O /OO 



Temperature. 



FIG. 32. Conductance-Temperature Curves for Various Electrolytes in 

 Liquid Ammonia. 



the conductance passes through a maximum in the neighborhood of 128. 

 For solutions of strong binary electrolytes in water, however, the maxi- 

 mum lies at much higher temperatures. 



Before proceeding to a detailed discussion of aqueous solutions, we 

 may consider solutions in other solvents. The conductances of a con- 

 siderable number of solutions in ammonia have been measured and a 

 maximum has been found in all cases. 2 The form of the curves will be 



*Sack, Wied. Ann. d. Phys. tf, 212 (1891). 



2 Franklin and Kraus, Am. Chem. J. tk, 83 (1900). 



