Section 65. The Conductivity Data. 163 



difference between the true value and that derived from the measurement 

 in the bomb would be substantially the same at different temperatures, 

 and whether it would be proportional to the conductance of the solution, 

 it has nevertheless seemed to us that values nearer the truth would be 

 obtained by applying a correction to our results with sodium hydroxide in 

 accordance with these assumptions than by leaving them uncorrected ; for 

 there is certainly some error in this direction. We recognize, however, 

 that there may still be an error in the corrected results as great as the 

 correction applied ; and it is expected that more accurate data will be later 

 obtained with a bomb containing the electrode within a cup to increase 

 the resistance. The percentage correction actually applied was equal to 5 

 times the conductance measured in the bomb ; that is, it was 0.5 per cent 

 when the conductance was 100,000 X 10~ 6 , 1 per cent when it was 

 200,000 X 10" 6 , etc. This correction has been introduced in table 51 in 

 the process of calculating the equivalent conductance from the observed 

 conductance. 



The results obtained in the bomb with the solutions of sodium hydroxide, 

 ammonium hydroxide, and ammonium chloride are given in tables 51-53. 



The first column gives the date of the experiment ; the second, the con- 

 centration at 4 in milli-equivalents per liter (the number of milli-equiva- 

 lents being based upon the atomic weights referred to oxygen as 16.000 

 and weights being reduced to vacuo) ; the third, the temperature corrected 

 for thermometric error at which the conductance was measured; the 

 fourth, the concentration at the temperature of the measurements, calcu- 

 lated by dividing the concentration at 4 by the corresponding specific- 

 volume ratio* and in the case of the sodium hydroxide measurements 

 at 156 applying the correction for the solvent in the vapor space ;f 



*The specific-volume ratio (that is, the ratio of the specific volume of the solu- 

 tion at the temperature of the measurements to that at 4) was assumed to be iden- 

 tical with that of pure water, the values determined by Noyes and Coolidge being 

 used at 218. This assumption is justified since they showed that up to 218 the 

 expansion of a 0.1 normal sodium chloride solution is identical with that of a 0.002 

 normal solution. The values of the ratio are 1.0013 at 18, 1.0125 at 51, 1.0257 at 

 75, 1.0432 at 100, 1.0660 at 125, 1.0978 at 156, and 1.1862 at 218. 



fSince the bomb was usually filled so as to have a vapor-space of only 1 or 2 c.cm. 

 at either 156 or at 218, the correction for the amount of the liquid vaporized was 

 insignificant and was not as a rule applied, the only exception being in the case of 

 the sodium hydroxide solutions at 156 where the vapor space was about 11 c.cm. 

 and where the concentration was correspondingly increased by 0.04 per cent. In 

 the case of the ammonia solutions the possibility existed that the solute also passed 

 into the vapor space in appreciable quantity; but this was disproved by comparative 

 conductivity measurements made with varying quantities (76 and 113 c.cm. at 18) 

 of solution in the bomb. Thus, a 97.07 millimolal NH 4 OH solution showed in the 

 bomb the following conductances, the usual procedure in heating being followed in 

 each case : 4969 and 4972, mean 4970 at 100 ; 4735 and 4735, mean 4735 at 156, 

 when 113 c.cm. at 18 were introduced : and 4964 and 4977, mean 4970, at 100 ; 

 and 4675 and 4703, mean 4689 at 156, when 76 c.cm. at 18 were introduced. There 

 is seen to be no difference at 100 and one of only 1 per cent at 156. Since the lat- 

 ter arises from a difference in vapor-space of 40 c.cm., it is evident that the error 

 would be inappreciable when the vapor-space was, as was usual, about 1 c.cm. 



