Measurements of the Equilibrium Constant for the Disproportionation Reaction of Mercury(I) Ion by using the Gas-Aqueous Distribution Equilibrium of Mercury(0)

Abstract

The disproportionation of mercury(I) ion into mercury(II) ion and mercury(0) was studied in a highly dilute mercury(I) perchlorate solution with concentrations ranging from 10^-7 to 10^-8molg. The equilibrium constant, [Hg²⁺][Hg]/[Hg₂²⁺], for the disproportionation reaction was determined by using both a disproportionation equation derived by the authors and the gas-aqueous distribution equilibrium of mercury(0) formed by the disproportionation of mercury(I) ions, which was measured by a cold-vapor atomic absorption spectrophotometer. The equilibrium constant was found to be (3.0±0.2)×10^-9mol/l at the ionic strength below μ=0.1 at 25°C. The mercury(0) distribution ratio, [Hg]_gas/[Hg]_aq, under the gas-aqueous distribution equilibrium conditions was found to be O.40+0.02 at 25°C.