Studies on Chlorate Cell Process IV. Effect of Neutral Salts on Conversion of Available Chlorine to Chlorate

Abstract

It has been shown that neutral salts, such as Nacl and and Naclo3 and their mixtures, cause an apparent increase in the thermodynamic dissociation constants of weak acids and bases. The pH value of aqueous salt solutions at fixed hydrogen ion concentration decreases linearly with increasing content of neutral salt and represents a linear function of the salt's heat of hydration (12). The hydrogen ion activity coefficient and, hence, the thermodynamic dissociation constants of weak acids and bases apparently follow a corresponding dependence. In solution for the electrolytic chlorate formation, the dissociation constant of hypochlorous acid is thus apparently enlarged by one order of magnitude. As a consequence, in solutions for the electrolytic chlorate production the optimal pH region for the conversion of available chlorine is shifted toward lower values (pH 5.7–6.1), as shown both in theory and practice. The same phenomenon is shown to be of some importance for what happens in the anode diffusion layer, where chlorine hydrolysis may hence be affected.