Abstract: Studies were made on the kinetics of CuO reacting with gaseous mixtures of SO2, O2 and N2 of different compositions at temperatures ranging from 200 to 700℃. At low temperatures the reaction product is basic copper sulfate. Copper Sulfate is found at high temperatures and only after a large amount of basic sulfate has been formed. After about 30% of the original CuO has been converted into copper sulfate, a hard non-permeable copper sulfate layer is produced around the sample. Further reaction is controlled by gaseous diffusion through this reaction product layer. The amount of basic sulfate and normal sulfate produced has been found to increase linearly with reaction time before the formation of the non-permeable layer. The rate of formation of basic sulfate in the low temperature range and normal sulfate in the high temperature range can be represented by the following equation. where Rav. is the time-average reaction rate in weight percent per unit time; psO2 and pO2 are the partial pressures of S02 and O2 respectively;k1 k2 and k3 are constants. A reaction mechanism has been postulated. The reaction rate is considered to be controlled by the formation of sulfate ion on the solid surface between the adsorbed SO2 on the oxygen ion and another oxygen ion. In the absence of O2 in the gas phase, Cu3O is also formed as a reaction product. As Cu2O is a p-type semiconductor, the reaction rate is increased under this condition. The reaction follows a different mechanism with SO3 in the gaseous mixture, to which the present conclusion does not apply.