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A kinetic study of the dissolution of zinc in aqueous ammonia and ethylenediamine Dilworth, Louis Rivet

Abstract

The kinetics of the dissolution of zinc in aqueous solutions of ammonia and ethylenediamine under oxygen pressure were investigated at a temperature of 25°C. The variables investigated included free amine concentration, oxygen pressure and stirring rate. Two regions of kinetic control were observed having different dependences on oxygen pressure. At low oxygen pressures, the rate of dissolution of zinc is first order in oxygen pressure, dependent on stirring rate and independent of the free amine concentration. At higher oxygen pressures, an adherent oxide layer is formed on the zinc surface and the rate of dissolution is first order with respect to free amine concentration and independent of oxygen pressure. These results indicate that at low oxygen pressures the rate is controlled by the diffusion of oxygen to the zinc surface; and at high oxygen pressures, the rate of reaction is chemically controlled at the film-solution interface.

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