246 



Conductivity of Aqueous Solutions. Part VIII. 



tilization of the solvent alone. In the case of hydrochloric acid at 260, 

 the observed change in conductance was only about three-fourths of that 

 which would have resulted from the volatilization of the solvent alone, 

 a fact which indicated some volatilization of the solute.* This was 

 allowed for in all the experiments with hydrochloric acid at 260 by 

 diminishing the calculated correction for solvent-vaporization by one- 

 fourth. 



No correction for conductance of the water was applied, except in the 

 case of the neutral salts used in determining the conductance-capacity. 

 Unusually good water was used for the very dilute solutions, the measured 

 specific conductance just before mixing being almost always below 0.5 X 

 10~ s , and in some cases as low as 0.3 X 10". 



The final values of the conductance were corrected for contamination 

 wherever the difference between the initial and final 18 values exceeded 

 0.25 per cent, by the arbitrary rule that the conductance at the highest 

 temperature of the experiment be increased by two-thirds of the percen- 

 tage change observed at 18, and at the next lower temperature by one- 

 fourth of that percentage change. No such correction was applied to the 

 results with hydrochloric acid, since there seemed to be no variation at 

 the higher temperatures corresponding to that at 18. 



The expansion of all the solutions on heating was assumed to be the 

 same as that of pure water and the change in concentration was calcu- 

 lated by dividing the concentration at 4 by the specific volume of pure 

 water at the temperature in question. f 



*The data upon which this conclusion is based are as follows: 



The concentrations were only approximately those given in the table. The specific 

 volume of the saturated vapor was taken as 85 at 218 and 39 at 260 upon the basis 

 of the estimates referred to in section 34, Part IV. 



fFor the specific volume the following values were used : 



18 1.0014 100 1.0431 260 1.277 



25 1.0029 128 1.0685 306 1.433. 



50 1.0119 156 1.0980 



75 1.0257 218 1.1862 



The values at 128 and 156 are derived by graphic interpolation from Hirn's 

 values [Ann. chim. phys. (4), 10, 32 (1867)] after correcting them to the pressures 

 of saturated vapor by means of the compression-coefficient of water, obtained by 

 extrapolating from the data of Pagliani & Vincentini given in the Landolt-Bornstein- 

 Meyerhoffer Tabellen. The values at 218 and 306 are those experimentally deter- 

 mind by Noyes & Coolidge; that at 260 was obtained by graphic interpolation. 



