388 PROCEEDINGS OF THE INDIANA ACADEMY OF SCIENCE. 



electrode or that of a 0.1 M HCl calomel electrode. Therefore any variations 

 in the potential of 



Ho— Pt— 0.1 M (HCl+KCl)— HgaCl.— Hg 

 with change in the relative amounts of HCl and KCl would be due to the 

 change in the potential of the hydrogen electrode, caused by the change in 

 the hydrogen ion concentration. The change in hydrogen ion concentration 

 corresponding to any change in the potential of the hydrogen electrode can 

 be readily calculated and it is therefore possible to compare the experimentally 

 determined hydrogen ion concentrations with those calculated on the isohy- 

 drie principle. Agreement would further confirm the equal dissociation of 

 the two solutions. Disagreement would indicate either a discrepancy in the 

 degrees of dissociation or a failure in the application of the isohydrie principle. 

 So far mixtures of the composition 



0.08 M H CI +0.02 M KCl 



0.05 M H CI +0.05 M KCl 



0.0:i M HCl +0.07 M KCl 



0.01 M HCl +0.09 M KCl 

 have been studied and rough agreement l)etween the calculated and experi- 

 mental values is obtained. Variations of the order of 1 % have not yet been 

 explained and the study is being continued in order to account for these 

 variations. At present it is thought that probably the variations are due to 

 changes in the potential of the calomel electrodes upon standing, su^h as 

 have been noted with 0.1 M HCl calomel electrodes. 



