Abstract: A new method called potentiometric stripping analysis (PSA)for determination of diffusion coefficients of metal in mercury is presented in this paper. The principle of the method is: amalgam in a hanging mercury drop electrode (HMDE) is carried out at first by electrolysis, then the potentiostatic circuit is disconnected and the amalgamated metals are oxidized consecutively by oxidizer added to the solution. The redox potential of HMDE is recorded on a high-impendence X-t recorder, the time (τ) between two consecutive equivalence is taked as signal of determination of diffusion coefficients of metal in mercury, which is based on the equation derived in this paper as follow:
τ=Kc_0°-r_0~2/15D_R
If graph of τ vs c_0° is made, intercept (τ_0) on coordinate of τ is derived by extending the curve of τ vs c_0° as for as c_0°→0, and D_R iscalculated according to:
D_R=-r_0~2/15τ_0
Diffusion coefficients D_R of some metals in single amalgam are determined by this method. The values of D_R are in agreement with those obtained by former researchaers. Diffusion coefficients of Zn and Cd in multi-amalgam are also determned. It is discorved that the values of diffusion coefficients of Zn and Cd in multi amalgamare almost the same as those in single amalgam.