Use of a Perchlorate-responsive Membrane Cell for the Determination of Activity Coefficients of Aqueous Perchloric Acid

Abstract

The e.m.f. of the membrane cell H2(l atm), HC104(/?h, fixed), ClO;-responsive membrane, HC1O4(/h2, variable), H2(l atm) has been measured in order to determine the mean molal activity coefficients for aqueous perchloric acid at 25°C. The liquid membrane used consists of a solution of tetraheptylammonium perchlorate in ethyl bromide, and is characterized by an ideally Nernstian response to the CIO; ions. The HC1O4 concentration range covered is 0.0001 to 10 mol/kg, a range which extends well below the lower concentration limit typical of the isopiestic method (0.1 mol/kg). The present e.m.f. method is applicable to activity coefficient determinations for perchlorates other than HC1O4.