Insoluble polyelectrolyte complexes were produced by admixture of (0.2 M) aq. solutions of poly(sodium phosphate) (PSP) and poly(4-vinylpyridinium chloride) (P4VPC) over the whole range of composition. Independent of the order of addition, the weights of isolated complex were approximately equal to those calculated on the basis of reaction stoichiometry. Stoichiometry was also confirmed by analysis of the supernatant liquid in conjunction with the weights of initial components and complex. Dissolution of the complex required a certain minimum hydrogen ion concentration obtained by using either a strong acid/base or a weak acid. Analysis showed that the starting materials were thereby regenerated. In dilute (1 x 10(-4) M) aq. solutions, the complex did not precipitate, but UV spectroscopy demonstrated its presence and its change of shape with time. (C) 1999 Elsevier Science Ltd. All rights reserved.