The Measurement of the Distribution Equilibrium Constant of Metallic Mercury for Hg(aq)(gas)

The gas-aqueous distribution equilibrium constant of mercury(0) was determined in the temperature range from 5 to 45 °C. The experiment was made by volatilizing metallic mercury dissolved in water to the gas phase, which was connected with the absorption cell in a cold-vapor atomic absorption spectrophotometer, and by measuring the absorbance under gas-aqueous distribution equilibrium conditions. The distribution equilibrium constant, [Hg]gas/[Hg]aq, was found, e.g., to be 0.40±0.02 at 25 °C. The effect of the concentration of NaCl on the distribution equilibrium constant was measured at 25 °C. The salting-out effect was found to be expressed by the Setschenow equation, and the salting-out coefficient was found to be 0.105.