Chloride and bromide complexes of zinc(II) and mercury(II) in aqueous ammonium nitrate melts

Abstract

The stability constants of species HgCl⁺, HgCl₂, in aqueous melts of NH₄NO₃,xH₂O (x= 2–5), and ZnCl⁺, ZnCl₂, ZnBr⁺, ZnBr₂(x= 1–3) have been determined at 55–85 °C from e.m.f. measurements of suitable concentration cells. The results for Hg^II chlorides are essentially in agreement with a quasi-lattice model of aqueous melts, but the zinc halide species behave anomalously: the chloride complexes are more stable than bromide complexes, and the first consecutive stability constants for ZnCl⁺ and ZnBr⁺ increase with temperature, in contrast to the behaviour of other divalent metal halides.