Section 20. Summary. 55 



temperatures there were considerable deviations between the observed and 

 calculated values. To make applicable the general function A A = 

 KA^C"- 1 (of which the van't Hoff function A A = Kh. C l is a special 

 case), it is necessary to vary the exponent n somewhat with the nature of 

 the salt and with the temperature. The values of n lie, however, between 

 1.40 and 1.50 for both salts at all temperatures. 



The conductance values extrapolated for zero concentration, and there- 

 fore the migration-velocities of the ions, were found to increase with the 

 temperature steadily, but not uniformly. It is shown that at any rate up 

 to 156 there is a rough parallelism between the equivalent conductance 

 of the ions and the fluidity (reciprocal of the viscosity) of the water as 

 determined by other workers ; but that the latter increases at all these 

 temperatures somewhat more rapidly than the equivalent conductance of 

 completely ionized potassium chloride. 



The ratio of the equivalent conductance of sodium and potassium chlo- 

 rides at zero concentration decreases from 0.84 at 18 to 0.96 at 306, show- 

 ing that the migration-velocities of the sodium and potassium ions are 

 slowly approaching relative equality. 



The degrees of ionization of the two salts are nearly identical (extreme 

 variation about 2 per cent) at all temperatures and concentrations. The 

 ionization in 0.08 normal solution has approximately the following values : 

 86 per cent at 18, 83 per cent at 100, 80 per cent at 156, 77 per cent at 

 218, 70 per cent at 281, and 63 per cent at 306. It is decreasing with 

 great rapidity at the higher temperatures. Its change with the concen- 

 tration is at all temperatures accurately expressed by an equation of the 



( C \ % 

 form r , K(Cy) m in which the exponent m always has values 



C (1 y) 



lying between 0.50 and 0.60. 



The specific volume of the 0.002 normal solutions, which can be 

 regarded as identical with that of pure water, was found to be 1.187 at 

 218, 1.337 at 281, and 1.437 at 306. The expansions of the two 0.1 

 normal solutions are substantially identical, but somewhat less than that 

 of water, as is shown by the fact that the ratio of their specific volumes 

 at 306 and 4 is 1.424, instead of 1.437. 



