CONDUCTIVITY AND VISCOSITY. 17 



Stephan, 1 in 1883, tried a third possibility, by using mixtures of alcohol 

 and water as a solvent. He found that the temperature coefficients of con- 

 ductivity and of fluidity (the reciprocal of viscosity) closely resembled each 

 other. He observed a minimum in his curves and proposed the formula : 



KH 



- = constant, to hold up to the minimum point, 



Krj 



and . = constant, to hold from that point on ; 



WKrj 



where K is the conductivity of the equivalent aqueous solution, k the con- 

 ductivity of the mixture, and H and 17 the corresponding viscosities ; w and 

 w' are the per cents of water in the given aqueous mixture and in the aqueous 

 alcoholic mixture of minimal fluidity, respectively. He believed that each 

 ion carries with it neighboring molecules of the solvent, and that ionic fric- 

 tion results from the friction between these and the rest of the solvent. 



Dutoit and Friderich 2 introduced the association factor and concluded that 



The values of MD for a given electrolyte dissolved in different solvents, are a direct 

 function of the degree of polymerization of the solvent and an indirect function of the 

 coefficient of viscosity of these solvents. 



A fourth method of changing the fluidity was resorted to by Rontgen, 3 

 and later by Warburg and Sach, 4 and more exhaustively by Cohen. 5 They 

 subjected the aqueous solution to high pressure. Cohen found that, at low 

 temperatures, the viscosity is decreased by the pressure, but that above 40 

 the viscosity increases with the pressure. In concentrated solutions of 

 sodium and ammonium chlorides the viscosity increases nearly proportional 

 to the pressure, and nearly independent of the temperature. Hauser 6 

 showed that, at 32, the pressure ceased to affect the fluidity of water. 



Grossman, 7 in 1883, recalculated Grotrian's results, and found that the 

 conductivity multiplied by the viscosity gave a constant independent of the 

 temperature, and that the temperature coefficients were the same to within 

 1 per cent. 



Arrhenius 8 worked with aqueous solutions to which small amounts of non- 

 electrolytes, such as acetone and methyl and ethyl alcohols, had been added. 

 He pointed out an empirical relation between the conductivity and the fluidity ; 

 but he saw that these quantities are not simply dependent on each other, 

 since the conductivities of dilute solutions of different salts are not the same. 

 This empirical relation was further developed by Euler. 9 



'Wied. Ann., 17, 673 (1883). 'Ann. d. Phys., 6, 597 (1901). 



2 Bull. Soc. Chim., [3], 19, 321 (1898). 7 Wied. Ann., 18, 119 (1883). 



8 Wied. Ann., 22, 510 (1884). 8 Ztschr. phys. Chem., 9, 487 (1892); 



4 Ibid., 22, 514 (1884). 1, 285 (1887). 



'Ibid., 46, 666 (1892). Ibid., 36, 536 (1898). 



