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.

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.

On a developpe une nouvelle methode de calcul pour determiner les constantes de formation de complexes en 6quilibre avec un precipite en solution aqueuse. Cette methode a kt6 appliqute h l'ttude des complexes ammonio et hydroxo-ammonio du zinc en presence de son hydroxyde. Les courbes de solubilite en fonction du pH et de pNH3 , , , ont 6tC Btablies au moyen de l'isotope 65Zn h 25 "C et force ionique unitaire avec NaC10,.A new method has been developed for the calculation of the formation constants of complexes inequilibrium with a precipitate in aqueous solution. This has been applied to the study of ammonio and ammonio-hydroxo complexes of zinc in the presence of the hydroxide. The curves of solubility vs. pH and pNH3 have been established by means of 65Zn at 25 "C and ionic strength 1.0 with NaC10,.