MIXTURES OF ELECTROLYTES MACGREGOR. 115 



mixtures, we must determine what the conductivities of Bender's 

 mixtures would have been if Kohlrausch had prepared and 

 measured them. To find this out as nearly as possible, I plotted 

 the data of the above table with Bender's conductivities as 

 abscissae, and the differences between them and Kohlrausch's 

 corresponding values as ordinates, and drew a smooth curve 

 through the points. By the aid of this curve I determined the 

 correction b of the table given below. This correction is of 

 course a more or less doubtful one ; for it is not certain that the 

 observations on mixtures suffered from the same unknown 

 source of error as the observations on simple solutions. It 

 seems probable however that they did ; and the results of the 

 table given below would appear to render it almost certain. 



It may be well in one case to give an example of the mode 

 of calculation. We may take for this purpose the mixture of 

 solutions containing each 1 gramme-molecule of salt. It is 

 found by the graphical process that the value of a/V for this 

 mixture is 0.718 gramme-molecules per litre and that the dilu- 

 tions in the mixture are 0.937 and 1.063 litres per gramme- 

 molecule for the Na Cl and K Cl respectively. The densities of 

 the constituent solutions were 1.0444 and 1.0401 respectively, 

 and that of the mixture 1.0422. The expansions per unit volume 

 between 15 and 20 were 0.0013569 and 0.0012489 respectively. 

 The values of the conductivity at infinite dilution, I took to be 

 1028 and 1216 respectively, according to Kohlrausch's observa- 

 tions. Hence the conductivity of the mixture 



2x10422 (1x0.118 x 0.937 x 1028 1UO718 x 1.063 x 1216\ ^ 

 * 2.0845 \ 1 + 0.6x0.00136 " 1 + 0.6x0.00125 / 



Bender's observed value (he used the same standard as 

 Kohlrausch) was 814. To this a correction of about 3 must 

 be applied to make the observation agree with the others of the 

 same series (correction a) and a correction of about- 3 to make 

 it comparable with a calculated value based on Kohlrausch's 

 data (correction b). Bender's reduced value is thus 808, which 

 differs from the calculated value by 1.2, or 0.15 per cent. 



