STUDIES ON METAL CARBONATE EQUILIBRIA 26 - THE HYDROGEN CARBONATE COMPLEX OF MANGANESE(II) IN ACID-SOLUTIONS AND A 3M (NA)CLO4 IONIC MEDIUM AT 25-DEGREES-C - DETERMINATION OF THE SOLUBILITY PRODUCT OF MNCO3(S)

Complex formation in the system Mn(Il)-H2O-CO2(g) has been studied in a 3 M ClO4- medium at 25-degrees-C using an EMF method. The equilibrium concentration of the H+ ions, [H+] = h, was measured using a glass electrode. The data could be explained by the chemical model given below. Mn2+ + H2O + CO2(g) half arrow left over half arrow right MnHCO3+ + H+, logbeta111 = -7.56 +/- 0.08. The equilibrium constant beta(pqr) refers to 3 M NaClO4 as solvent. The error quoted is a maximum deviation evaluated graphically. The Mn(II) system was studied in the range 3.0 < - log h < 6.1. The total concentration of the Mn2+ ions, B(T), was kept constant during the titrations at 0.1, 0.2 and 0.3 M, respectively. The partial pressure of CO2(g), a, was kept constant and had the following values: 0.3 and 0.5 atm, respectively, at each B(T)-level. The solubility studies in 3 M (Na)ClO4 resulted in the following results: MnCO3(S) half arrow left over half arrow right Mn2+ + CO32-, log K(so) = -9.78 +/- 0.04. Mn2+ + CO32- half arrow left over half arrow right MnCO3(aq), log beta1 = 3.54 +/- 0.19. Mn2+ + HCO3- half arrow left over half arrow right MnHCO3+, log beta11 = 0.32 +/- 0.08.