The nature and stability of cadmium sulphide complexes in aqueous solutions have been investigated. The total concentration of the metal in solution was determined a t constant temperature and ionic strength, and a t various pH values, by a radioactive tracer technique.

A mathematical treatment of solubility curves of sulfides is introduced for the determination of formation constants of complexes in solution. As an example, this theoretical method is used in the determination of the species in equilibrium in solution with a precipitate of zinc sulfide (β-ZnS). The excess of sulfide in solution varies from 0.0004 M to 0.01 M. The presence of Zn2+ is noted in acidic solution, followed by the presence of ZnS.H2O or Zn(HS)(OH) for the rest of the pH scale. The solubility product of ZnS and the formation constant of Zn(HS)(OH) are given for an ionic strength 1.0 (NaClO4) at 25 °C.

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Recu le 25 aoClt 1966On a procCdC A une dCtermination des complexes hydroxo d'argent et de zinc A partir des courbes de solubilitC des hydroxydes en fonction du pH, A 25 "C et force ionique unitaire (NaC104). On a calcul6 les produits de solubilit6 des hydroxydes et les constantes de formation des espkces AgOH, Ag(0H)z-, ZnOH+, Zn(OH)z, Zn(0H)r-et Zn(OH)42-.The hydroxo-complexes of silver and zinc are determined from a plot of their hydroxide solubility curves vs. pH, a t 25 OC and unit ionic strength (NaC104). The hydroxide solubility products and the formation constants of AgOH, Ag(0H)z-, ZnOHf, Zn(OH)z, Zn(OH)a-, and Zn(OH)42-are calculated.

The aqueous solubility of the system silver selenide has been investigated in an inert atmosphere of nitrogen at a unit molar ionic strength and constant temperature of 25° C. The experimental evidence indicates the formation of two aqueous species [Ag2(HSe)(OH)], and [Ag(Se)2(OH)]4− in contact with the precipitated selenide in different regions of acidity. The former exists in acidic medium and has a pβ value of 48.49 ± 0.10 while the latter is stable only in alkaline conditions and has a pβ value of 24.07 ± 0.19. A mathematical treatment has been elaborated to identify and calculate the stability constants of such selenide complexes formed through a heterogeneous equilibrium.