312 ON THE CALCULATION OF THE CONDUCTIVITY OF 



The foregoing table, I, contains the necessary data for the 

 drawing of the ionic concentration-dilution curves for each salt. 

 Dilutions are expressed in terms of litres per equivalent gramme- 

 molecule of anhydrous salt at 18C. The conductivities are 

 specific molecular conductivities (i. e. per gramme-equivalent) at 

 18C, expressed in terms of 10" 8 times the specific conductivity 

 of mercury at 0C. The concentrations of ions are the ratios 

 of the specific molecular conductivity, to specific molecular con- 

 ductivity at infinite dilution, divided by the dilution. 



Observations on the Double Sulphate Solutions. 



Table II contains both the data for, and the results of, the 

 calculation of the conductivity of each solution of the double 

 sulphate examined, together with the observed values, and the 

 differences between observed and calculated values, expressed 

 as percentages. The concentrations of solutions are expressed in 

 terms of equivalent gramme-molecules of anhydrous salt per 

 litre at 18C. The conductivities are specific conductivities at 

 18C, expressed in terms of 10~ 8 times the specific conductivity 

 of mercury at 0C. The concentration of ions common to the 

 two electrolytes in a solution, and the dilutions of the electro- 

 lytes in the solution, are obtained by Prof. MacGregor's graphical 

 method, on the assumption that a solution of double salt may 

 be made by mixing equal volumes of equi-molecular solutions of 

 the simple salts, and that, on mixing, the double salt does not 

 form The former is the number of dissociated gramme-equiva- 

 lents of either electrolyte, which on that assumption would be 

 present in the solution, divided by the volume in litres of the 

 portion of the solution occupied by it. In any one solution it 

 will have the same value for both electrolytes. The latter are 

 the volumes in litres of the portions of the solution occupied by 

 the respective electrolytes, divided by the number of gramme- 

 equivalents present. In each solution they will have different 

 values for the two electrolytes. The product of the former into 

 the value of the latter, in the case of either electrolyte gives the 

 ionization coefficient for that electrolyte in the solution. 



