310 ON THE CALCULATION OF THE CONDUCTIVITY OF 



More dilute solutions were prepared from this one by adding 

 water, and their concentrations calculated. Check analyses, 

 however, were made after any portion had gone through a 

 numher of dilutions, and, if found necessary, the calculated con- 

 centrations were corrected from these results. 



As the method of calculation required a knowledge of any 

 appreciable change of volume which would occur on mixing 

 simple solutions of each of the salts, of such strength as to form 

 a solution of the same concentration as the solution of the double 

 salt under investigation, density determinations were made of 

 a number of such solutions, before and after mixing. These 

 measurements were carried out with Ostwald's form of Sprengel's 

 Pyknometer. They might be in error by about 5 in the tifth 

 decimal place. No change of volume was found to occur on 

 mixing the most concentrated solutions examined which would 

 appreciably effect the calculation of the conductivity. The 

 density of a mixture of the constituent solutions of the double 

 sulphate was found in the case of some of the stronger solutions 

 (the only ones tested) to be the same, within the limits of experi- 

 mental error, as the density of a solution of the double salts of 

 the same concentration. 



For the simple solutions the ionization coefficient was taken 

 to be equal to the ratio of the specific molecular conductivity to 

 the specific molecular conductivity at infinite dilution. The 

 values of the molecular conductivity at infinite dilution used in 

 the calculations were : 1280 x 1CT 8 , and 1100 xlO~ 8 for Potas- 

 sium and Copper Sulphate respectively, as determined by 

 Kohlrausch.* I was not aware, at the time the calculations were 

 made, that he had given 1270 X 10~ 8 , and 1120 X 10~ 8 , as better 

 values for these salts.f I have, however, repeated some of the 

 calculations and find that the difference caused by using these 

 later values are in all cases less than 0.06 per cent. 



* Wied. Ann., Vol. 26. p. 204. 



t Wied. Ann., Vol. 50 (1893), p. 406. 



