The oxidative dissolution of cobalt oxalate and manganese oxalate in acetic acid solutions with a flow of oxygen-nitrogen mixing gas at pressure of 1.5 MPa was studied. Experiments investigating the following parameters: the stirring speed, the reaction temperature, the concentration of oxygen containing gas, the concentration of hydrobromic acid and leaching time, showed that cobalt oxalate and manganese oxalate can be dissolved completely in acetic acid solutions at the best conditions. It was found that the dissolution rate increased with increasing reaction temperature, and with decreasing concentration of HBr. It was observed that the presence of oxygen was necessary to reaction occur, but a concentration of O-2 beyond about 3% has almost no effect on the dissolution rate. It was determined that the first-order pseudo-homogenous reaction model can describe the dissolution rate of cobalt oxalate and manganese oxalate during the leaching. The data obtained for the oxidative dissolution of oxalates indicated that the process is controlled by the dissolution rate of oxalate salts into acetic acid solutions. (c) 2006 Elsevier B.V. All rights reserved.