US EPA

8318391 

Journal Article 

Estimation of medium effect on dissociation constant of ammonium ion and formation constants of silver(I)-ammine complexes in aqueous solution 

Maeda, M; Nakagawa, G; Biedermann, G 

1983 

1 

Journal of Physical Chemistry
ISSN: 0022-3654 

87 

1 

121-125 

English 

10.1021/j100224a028 

So that information concerning the influence of electrolytes on complex formation equilibria could be obtained, the equilibrium constants of the reactions, NH4+ = H+ + NH3 (Ka), Ag+ + NH3 = AgNH3+ (β1), and Ag+ + 2NH3 = Ag(NH3)2+ (β2), were determined at 25°C by glass electrode potentiometry in LiNO3, NaNO3, KNO3, LiClO4, and NaClO4 aqueous media of different concentrations (0.5-5 mol dm-3). The pKa values increased linearly with the increase of the electrolyte concentrations and showed little difference with different kinds of electrolytes. As for the Ag+-NH3 systems the formation constants were considerably lower in the nitrate media than in the perchlorate media. In the ionic media, with the exception of LiNO3, the formation constants continued to increase monotonously with rising electrolyte concentrations. On the contrary, in the LiNO3 media, they appeared to decrease with electrolyte concentrations. These variations in the constants were discussed in terms of the specific interaction theory, in which interactions between ions of opposite charges were assumed. The constants thus calculated showed a reasonable agreement with the experimental ones, although in most cases the deviations between the measured and estimated values exceeded by far the experimental uncertainties. © 1983 American Chemical Society.