AbstractThe persulphate‐bisulphite‐Cu2⊕ initiated emulsion polymerization of vinyl chloride has been investigated in the presence of a metal‐ion complexing agent (trisodiumcitrate). In the range of concentrations investigated, the rate of radical production from the redox system was found to be 2nd order with respect to the concentration of NaHSO3 and independent of the persulphate concentration. The effect of the concentrations of citrate and copper ions was found to be strongly dependent on the ratio [citrate]t/[Cu]t (index t indicating total added amounts). In borax and phosphate buffer, the rate of polymerization was found to be proportional to [Cu]t1/4·[citrate]−1/2 at ratios larger than about ten. When the ratio approaches unity, an abrupt increase in rate was observed. A kinetic scheme based on the equilibrium reaction is discussed. The effects of [Cu]t and [citrate]t, as predicted by this scheme, were calculated by computing numerical values of [Cu2⊕] according to the above equilibrium. This proved the theory to be in good agreement with the experimental results.