This paper describes a study of the kinetics of oxidation of hydrogen chloride over unsupported melts containing copper, potassium and lanthanum chlorides. It is shown that kinetic data may be interpreted by assuming that the equilibrium: CuCl, = CUCI + Cl, is maintained at all times between catalyst melt and gas and that the overall rate of hydrogen chloride oxidation is determined by the rate at which the melt absorbs oxygen. Rate constants calculated from the overall kinetic data agree weII with values obtained previously from a study of the kinetics of oxygen absorption. The activity of the catalyst is promoted by the addition of lanthanum chloride and it is shown that this effect is due to catalysis of the oxygen absorption step. The complex effect of temperature on the rate of the overall reaction may also be accounted for satisfactorily in terms of this mechanism. For melts containing equimolar amounts of potassium and copper chlorides it is shown that the apparent activation energy is.approximately 28 kcal per mole of hydrogen chloride oxidised. The conclusions from this studv should be applicable to supported Deacon catalysts which . have the same active components.