358 ME. W. C. D. WHETHAM ON THE IONIZATION OF 



For each set the numbers for m l , corresponding to the concentrations used, were 

 calculated, and the proper values of the ionization coefficients estimated from the 

 smoothed curves. 



Table XII. shows the approximate equivalent conductivities in absolute C.G.S. 

 units. In order to obtain these numbers, a knowledge of the cell constant or 

 " resistance capacity " of the apparatus is necessary. This knowledge is not 

 needed for deducing the ionizations, and therefore no arrangements were made in 

 planning the investigations for accurately obtaining it. Whenever the apparatus 

 was dismounted for cleaning or other purposes, and set up again, it was found that a 

 new measurement of the volume was necessary, slight differences in adjustment 

 making the volume of water contained in it change by three or four-tenths of a 

 cubic centimetre. Since a knowledge of the amount of solvent used is necessary for 

 accurate estimation of the concentrations of the solutions, this redetermination of 

 volume was always made. The variation in volume would involve a slight change in 

 the cell constant of resistance, which, not being needed for the main purpose of the 

 work, was only once determined. The conductivity of solutions of copper sulphate 

 was, as already explained, measured at a temperature of 18 as well as at the 

 freezing point, and a comparison could thus be made between the equivalent conduc- 

 tivity of solutions of known strength, as measured in the arbitrary cell units of this 

 investigation, and the equivalent conductivity of solutions of the same strength 

 as given by KOHLRAUSCH* in absolute units. Three values obtained for the 

 conversion factor at three different concentrations were 2'345, 2'322 and 2'313, each 

 multiplied by 10 ~ n , giving a mean cell constant of 2'327 X 10" 11 . The variation 

 between the three values depends on the slight difference in slant between the 

 two curves for 18, as shown in the diagram (p. 350). 



This mean value of the cell constant was used for calculating the equivalent con- 

 ductivities for all substances except potassium chloride, the greatest variations in the 

 weight of water contained in the cell during these observations being from 21 9 '25 

 to 219 '61. Potassium chloride was investigated at an earlier date, before a change 

 in arrangement had considerably altered the constant of the cell. In the case of 

 this salt, however, KOHLRAUSCH has given equivalent conductivities for a few concen- 

 trations at as well as at higher temperatures, t and thus a new determination of 

 the cell constant was made, using a solution whose concentration was one hundredth 

 normal. The constant was found to be 2*161 X 10 ~~ n , and from this the absolute 

 equivalent conductivities for the other concentrations of that salt were calculated 

 from the present determinations of the ionization. 



In conclusion I have to thank my wife for constant help, both with the experi- 

 ments and calculations, Mr. E. H. GRIFFITHS for much assistance and many valuable 

 suggestions, Mr. GREEN, for distilling a considerable part of the water used and 



* ' Ann. der Physik und Chemie,' N.F., vol. 66, p. 813, 1898. 

 t ' Ann. der Physik und Chemie,' N.F., vol. 64, p. 441, 1898. 



