AbstractThe electromotive force of the cell,Pt/NaHSeO3, QH/Ag2SeO3(s)−Aghas been calculated from the cells,Hg‐Hg2Cl2(s)/KCl(satd.)/KNO3(m)/NaHSeO3(m)/Ag2SeO3(s)‐Ag,and Hg‐Hg2Cl2(s)/KCl(satd.)/KNO3(m)/NaHSeO3(m), QH/Pt at 25°C in concentrations of sodium biselenite, ranging from 10−2to 10−3M.The standard potential of Ag‐Ag2SeO3/SeO3= electrode has been determined asE°= −0.3629 volt. The solubility‐product constant of silver slenite and the activity coefficient of selenous acid at varying concentrations