Section 95. Final Values of Equivalent Conductance. 261 



95. FINAL VALUES OF THE EQUIVALENT CONDUCTANCE AT ROUND 



CONCENTRATIONS. 



The mean values of the equivalent or molal conductance given in tables 

 101 to 107 have been reduced to round concentrations by the help of coeffi- 

 cients derived from curves obtained by plotting A against some function 

 of the concentration (C), or of the product AC. The error introduced in 

 reducing in this way to round concentrations probably exceeds 0.1 or 0.2 

 per cent only for those values, inclosed within parentheses in the table 

 below, which it was necessary to correct for a fairly large difference in 

 concentration. 



The equivalent conductances at zero concentration (A ) have been 

 obtained in the cases of nitric acid, phosphoric acid, and barium hydroxide 

 at temperatures up to 15G by extrapolation upon plots of 1/A against 

 (AC) 11 ' 1 , as described in section 17, Part II (except that those for barium 

 hydroxide at 75 and 128 were obtained, by interpolation, from a plot of the 

 other A values against the temperature). The A - value for hydrochloric 

 acid at 306 was obtained in the same way ; but to get that at 2G0 the value 

 of the exponent n was assumed to be 1.50, since the data were not sufficient 

 to determine this with accuracy. The A - values for nitric acid at 218 

 and 306 were assumed to be 97 per cent of those for hydrochloric acid at 

 these temperatures, just as they are at 100 and 156. Owing to the con- 

 tamination in the more dilute solution, the A -values for barium hydroxide 

 at the higher temperatures are only rough approximations; and owing to 

 the long extrapolation, those for hydrochloric and nitric acids at 260 and 

 306 may well be in error by two to three per cent. The A - values for 

 sulphuric acid at 18, 100, 156, 218 and 306 were obtained by the 



^ n A H 2 SO 4 = A HCl + A-0K2SO4 A KCl 



using the values for hydrochloric acid, potassium sulphate, and potassium 

 chloride given in table 36, ( 54, Part V), table 22, ( 41, Part IV), and 

 table 9 (16, Part II), respectively. Those at the intermediate tempera- 

 tures were obtained from the others by graphic interpolation. 



The final values so obtained are all given in tables 108 and 109. The 

 temperatures are those of the hydrogen-gas scale. The concentration is 

 expressed in milli-equivalents (or milli-formula- weights) of solute per 

 liter of solution at the temperature of the measurement, the atomic weight 

 of oxygen being taken as 16.00 and the weights of substances being cor- 

 rected for air buoyancy; milli-formula-weights per liter are given for 

 phosphoric acid and potassium hydrogen sulphate, milli-equivalents per 

 liter for all the other substances. The equivalent or molal conductance is 

 expressed in reciprocal ohms ; the molal conductance is given in the case 

 of phosphoric acid and potassium hydrogen sulphate, the equivalent con- 

 ductance in all other cases. 



