THE CONDUCTANCE OF SOLUTIONS VISCOSITIES 139 



centrations, assuming that the conductance of the solvent is zero, or has 

 been otherwise corrected for, differs for different electrolytes, and is, in 



R P 



general, the greater, the greater the value of -5 . Thus the limit ap- 



/tp=i 



preached for hydrochloric acid at a pressure of 3000 kilograms per square 

 centimeter is approximately 17 per cent, while that of sodium chloride 

 is approximately 8 per cent and that of potassium chloride 9 per cent. 



Since in dilute solution the effect due to - T - is the same as that in pure 



v Ap 



water, it follows that these differences are due to differences in the vis- 

 cosity effect as illustrated in Figure 28. In the case of hydrochloric 



acid, the value of y -r passes through a flat maximum at a concentration 



in the neighborhood of 0.5 normal. 



In non- aqueous solutions the order of the viscosity effects differs 

 from that in aqueous solutions, chiefly owing to the fact that with in- 

 creasing pressure the viscosity of the solvent medium increases and con- 

 sequently the speed of the ions is reduced with increasing pressure. In 



*f> 



Figure 30 30 are shown values of the ratio ^ for solutions of 0.002 N 



Kp=i 



tetramethylammonium iodide and 0.1 N malonic acid in ethyl alcohol. 

 As was the case with water, the curve for weak electrolytes lies below 

 that for strong electrolytes. With increasing temperature, however, the 

 order of the curves is reversed with respect to their order in water; that 



R v 



is, the ratio decreases both in the case of strong and weak electro- 



Kp=i 



lytes. The curves are very nearly linear for solutions of strong electro- 

 lytes but are convex toward the axis of pressures for solutions of weak 

 electrolytes. This form of the curve is accentuated in solutions in sol- 

 vents of high viscosity ; as, for example, amyl alcohol, for which values of 



R v 



^ are represented in Figure 31. 31 In this case, the curves for malonic 



acid at higher temperatures exhibit a minimum, while the curves for 

 tetramethylammonium iodide are distinctly convex toward the axis of 

 pressures. It is evident that at pressures beyond 3000 kilograms per 

 square centimeter the curve for malonic acid in ethyl alcohol would 

 likewise pass through a minimum. The observed phenomena in non- 



Schmidt, Ztschr. f. phys. Ghent. 75, 319 (1910). 

 11 /bid., loc. cit. f p. 320. 



