TEMPERATURE COEFFICIENTS. 165 



Since Arrhenius made these measurements, maxima in conductivity have 

 been found for solutions of copper sulphate and for a number of organic acids. 

 The maximum conductivity of most aqueous solutions, however, is at so 

 high a temperature that experimental difficulties have prevented the verifica- 

 tion of the above theory of Arrhenius for many electrolytes. 



Maxima of conductivity have been found by Miss Maltby, 1 Hagenbach, 2 

 Noyes and Coolidge, 3 and others, all working at high temperatures. 



In the case of non-aqueous solvents there is more evidence available for 

 the existence of conductivity-temperature curves, containing maxima. 



Franklin and Kraus 4 found that, at high temperatures, the conductivity 

 of solutions in liquid ammonia decreases with rise in temperature. Miss 

 Maltby 5 showed that, at ordinary temperatures, the conductivity of an ethe- 

 real solution of hydrochloric acid decreases as the temperature rises. Cat- 

 taneo 6 obtained negative temperature coefficients in ether and alcohol. 



Kraus, 7 in his investigations of solutions in methyl and ethyl alcohols, 

 also found that the conductivity passes through a maximum with rise in 

 temperature. 



Jones 8 explains these maxima in the conductivity curves thus : 



The ions move faster and faster with rise in temperature, increasing the conductivity. 

 The association of the solvent becomes less and less with rise in temperature and, con- 

 sequently, its dissociating power becomes less and less. This, of course, diminishes the 

 conductivity. The maximum in the conductivity curve represents the temperature at 

 which these opposite influences become equal. 



In a very recent article, Jones and West 9 have pointed out the effect of 

 temperature on dissociation, and have worked out a large number of tempera- 

 ture coefficients of conductivity in aqueous solutions. They employed 32 

 substances, inorganic and organic, with very different degrees of dissociation. 

 The range of temperature over which their investigation extended was from 

 to 35. They found that, while conductivity increases with rise in tempera- 

 ture, dissociation decreases with rise in temperature. 



Jones 10 has recently pointed out the bearing of hydrates on the temperature 

 coefficients of conductivity of aqueous solutions. Jones and West, in their 

 work, showed that with rise in temperature there was a decrease in dissocia- 

 tion. Therefore, the increase in conductivity with rise in temperature is pri- 

 marily due to an increase in the velocities with which the ions move. The velocity 

 of the ions is conditioned chiefly by the viscosity of the medium and the size 



1 Ztschr. phys. Chem., 18, 155 (1895). "Rend. Lincei [5], 2, 1, 295 (1893); [5], 



2 Ann. d. Phys., 5, 276 (1901). 2, 2, 112 (1893). 



3 Ztschr. phys. Chem., 46, 323 (1904). 7 Phys. Rev., 18, 40 (1904). 



Journ. Amer. Chem. Soc., 26, 134 (1904). 8 Amer. Chem. Journ., 31, 584 (1904). 



4 Amer. Chem. Journ., 24, 83 (1900). Ibid., 34, 357 (1905). 



6 Ztschr. phys. Chem., 18, 133 (1895). "Amer. Chem. Journ., 35, 445 (1906). 



