DETERMINATION OF THE ASSOCIATION CONSTANT OF SULFURIC-ACID

The activities of HC1 and H2SO4 in aqueous solutions of HC1-H2SO4 and H2SO4-HC1O4, respectively, were measured at 298 K by an electromotive force (emf) method. Using the activity data, the association constant, K*H 2SO 4 was calculated as a function of the effective ionic strength of the solution by a method similar to that proposed by Johnson and Pytkowicz. The association constant of H2SO4, which corresponds to the reciprocal value of the first ionization constant of H2SO4, decreased with an increase in the effective ionic strength and was correlated to the effective ionic strength, I e (mol dm-3), as follows: log K*H 2SO 4 = 0.42 - 0.91Ie, 0 Ie1 The mean free activity coefficients of H2SO4 were calculated from the association constant of H2SO4 and were found to decrease with an increase in the effective ionic strength. © 1990 The Minerals, Metals & Material Society.