NOTES AND COOLIDGE. — ELECTRICAL CONDUCTIVITY. 219 



The ratio of the conductivities of potassium and sodium chlorides at 

 infinite dilution decreases from 1.19 at 18° to 1.04 at 306°, showing 

 that the migration velocities of the sodium and potassium ions are slowly 

 approaching equality. 



The degrees of dissociation of the two salts are nearly identical (ex- 

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

 The dissociation in 0.1 normal solution has approximately the following 

 values: 84 per cent at 18% 79 per cent at 140°, 74 per cent at 218°, 

 67 per cent at 281°, and 60 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 the equation 

 (1 - x) / C" = K. 



The conductivity of the vapor over a 0.1 normal potassium chloride 

 solution at 306° is too small to be observed with the present apparatus: 

 its specific conductivity is certainly less than 2-,joVo^ P^^^ of that of the 

 liquid. 



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

 regarded as identical with that of pure water, was found to be 1.186 at 

 218°, 1.336 at 281°, and 1.434 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 1.422, instead of 1.434. 



This investigation is being continued with the co-operation of others. 

 During the coming year other di-ionic salts and some tri-ionic salts will 

 be investigated in the same manner. A separate research will deal 

 with weak acids and their neutral salts with the aim of studying hydroly- 

 sis and the dissociation-constant of water. Another line of work to be 

 carried out with the bomb will consist in the determination of the 

 dielectric constant of water up to 306°. Then the attempt will be made 

 to extend all these measurements to the critical temperature. 



September, 1903. 



