CHEMISTRY. 



333 



conductance of a salt at any concentration to that approached at zero 

 concentration, commonly employed as a measure of ionization, is not 

 even approximately equal to the ionization in the case of largely 

 ionized substances; or at any rate that this ratio is not even roughly 

 proportional to the chemical activity or mass-action of the ions in 

 determining equilibrium. Certain anomalies long known had pre- 

 viously made it evident that this conclusion must be true, but experi- 

 mental data were lacking which would make possible a quantitative 

 comparison of the conductance-ratio of these substances with their 

 ion activities. These activities can be derived from studies of chemical 

 equilibria or from the values of the electromotive forces of voltaic cells 

 in which the substances are involved ; but the only previously existing 

 data of a character suitable for the comparison were those resulting 

 from a research by Maclnnes and Parker on the electromotive force of 

 cells involving solutions of potassium chloride. The investigations 

 on the electromotive force of cells carried out under the auspices of the 

 Carnegie Institution of Washington have now led to additional results 

 with three other substances of various chemical types, which enable 

 more general conclusions to be drawn. 



The following brief table shows the character of the results obtained 

 in these researches, which were carried out at the Massachusetts 

 Institute of Technology by Dr. James A. Beattie and Dr. Ming Chow, 

 with the cooperation of Dr. Duncan Maclnnes. Under the heading 

 "Ion-activity coefficients" are given the factors, derived from the 

 electromotive measurements, by which the concentration of the sub- 

 stances must be multiplied to give what may be called the effective 

 concentration of the ions in determining chemical equilibrium and other 

 thermodynamically related properties. Under the heading ''Conduc- 

 tance-viscosity ratio" are given the above-mentioned conductance- 

 ratios corrected for the viscosity of the solution through which the 

 ions are moving. 



From these data may be drawn the general conclusions that the 

 conductance-ratio can no longer be regarded as even an approximate 

 measure of the activity of the ions of largely ionized substances in their 



