The influence of pH on metal replacement of Cu and Hg was investigated. Percentage recovery of Hg complex showed the maximum at pH 10.Hg complex was formed instantaneously by the quantitative replacement of Cu from Cu and it was well bissolved in CCl media at pH 10.It is assumed that the reaction to form this complex could have competed against hydroxide precipitation above pH 10 and acidic pH, as the sulfur atom in chelating site of DDTC has more affinity power with proton at a higher concentration of protons.