Based on Equation , the mole ratio of malonic acid to H2O2 must be at least 1:2 for efficient generation of peroxymalonic acid which will lead to effective oxidative leaching of Cu(0) to Cu(II). However, at lower ratios, for example at a high concentration of malonic acid, but a lower concentration of H2O2, the generation of peroxymalonic acid will be low leading to poor leaching of Cu.