A method for the separation and determination of small amount of zinc in nickel-plating baths is here reported.The dried sample is fused with sodium hydroxide and the water extract is, after suitable treatments, titrated amperometrically with K₄Fe(CN)₆, using a stationary platinum micro-electrode, while the solution is stirred.The optimum conditions are as follows:applied voltage =+0.7 volt, and the supporting electrolyte should be about 0.5 N in NaCl and 0.4 N in H₂S0₄.With.about 0.5% Zn in sample, the relative precision of the determination lies within ±2%.The whole process may be accomplished in 40 minutes.