ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Heterogeneous inorganic systems. 6. Effect of cations on the formation of hydrogen phosphites in saturated aqueous solution

M. Ebert

Department of Inorganic Chemistry, Faculty of Natural Sciences, Charles University, CS-128 40 Prague

Abstract: The effect of the cations Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, NH₄⁺, Tl⁺, Mg²⁺, Ca²⁺ , Sr²⁺ and Ba²⁺ on the formation of hydrogen phosphites in saturated aqueous solution has been studied using solubility diagrams in ternary systems containing phosphite, phosphorous acid, and water. This influence has been evaluated employing the relationship between the effective polarization strength of the cations, considering the mode of their hydration, Pef, and the composition of the saturated aqueous solution at invariant points of the solubility curve at the beginning of the hydrogen phosphite formation. The composition of the saturated solution has been expressed in terms of the ratio of the stoichiometric ratio of the phosphorous acid and phosphite amounts, R_stoich, and the real mole ratio of their amounts, R_rea, M = R_stoich,/ R_real. It has been found that the relationship between the effective polarization strength and quantity M can be expressed for the studied set of cations by the equation M= 1.01(10⁵ . P_ef /pm^-2 )-2.51 It follows from this dependence that the effective polarization influence of the cations under the given conditions favours the formation of hydrogen phosphites and increases the strength of their hydrogen bonding, as observed earlier in a study of the changes in the standard Gibbs energy for the corresponding phase reactions.

Full paper in Portable Document Format: 421a21.pdf

Chemical Papers 42 (1) 21–28 (1988)