Investigations into the reduction of high concentration aqueous copper sulfate solutions with hydrogen, carbon monoxide and mixtures of these gases were conducted. The effect of increasing the copper sulfate concentration was to enhance the rate of reduction in both the hydrogen and carbon monoxide systems. The rate of reduction was increased by increasing pressure, temperature, and the concentration of ammonium sulfate buffer. Under mixtures of hydrogen and carbon monoxide the rate of reduction was intermediate between the rate under pure hydrogen and pure carbon monoxide. Based on the reaction mechanisms and rate equations developed by previous investigators a mathematical model of the reduction processes under hydrogen and carbon monoxide was developed. By fitting the model to the experimental results, rate constants for the high concentration reduction were determined. The use of carbon monoxide, with or without hydrogen, was found to reduce or minimize the plastering problem associated with the hydrogen reduction of copper. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate