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Kinetics of the dissolution of copper in aqueous aliphatic amines, and catalytic reduction of nickel ion by molecular hydrogen Sircar, Sisir Coomar

Abstract

Kinetics of the Dissolution of Copper in Aqueous Aliphatic Amines. An investigation was made of the dissolution of copper metal in aqueous solutions of methyl, ethyl and n-butyl amine and ammonia, as well as in solutions of their aminium and ammonium ions, under oxygen pressure. Study of the kinetics of the dissolution was carried out over a wide range of concentrations. It was observed that there are two regions of oxygen pressure dependency of the rate. The range of oxygen pressure, where rate is independent of oxygen pressure, was investigated in detail. The rate process has been established to obey the relation R = [formula omitted] [k₂(A) + k₃ (AH⁻⁺)] for all the systems studied. A mechanism for the dissolution reaction has been proposed. Catalytic Reduction of Nickel Ion by Molecular Hydrogen. The rate of precipitation of nickel from salt solution by molecular hydrogen in the presence of catalyst has been investigated over a wide range of concentrations. The variables studied are concentration of nickel, hydrogen pressure, amount of catalyst, concentration of- hydrogen ion and temperature. The rate of reduction is found to obey an equation of the form: [formula omitted] = -k₁[S][PH₂]½[Ni⁺⁺] + k₂[S][H⁺] The activation energy is found to be 25±2 kcal/mol. The equilibrium constant k for the reaction Ni⁺⁺ H2 Ni° + H₂ ⇌ Nº + 2 H⁺ is found to be 4.65 x 10⁻⁶ atm⁻¹ at 140°C.

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