A polyelectrolyte complex (PEC) was formed by mixing aqueous solutions of the polyanion poly(sodium phosphate) with the polycation poly(2-vinylpyridinium chloride). Conductometric and potentiometric titrations indicated the electrochemical end point of each titration. In all cases the end point occurred at a unit molar ratio of polyanionic to polycationic groups that was approximately one. The stoichiometry was also confirmed by analysis of the supernatant liquid in conjunction with the weights of the initial components and complex. An analysis showed that the starting materials were regenerated after dissolution of the complex with a 2M HCl solution. The interaction of the bivalent cupric ions with PEC were also investigated. (C) 2002 John Wiley Sons, Inc.