Zur Thermodynamik der Metallcarbonate. 4. Mitteilung. Potentiometrische Untersuchungen am System Mn 2+ CO 2 H 2 O

The solubility and the complex equilibria in the system Mn 2+ ‐CO 2 ‐H 2 O have been investigated at 25°C in solutions of the constant ionic strength 3 M (Na)ClO 4 . From experimental data the following values for equilibrium constants and Gibbs free energies of formation are deduced:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm MnCO}_{{\rm 3}\left({{\rm ppt}{\rm .}} \right)} :{\rm log}\left[{{\rm Mn}^{{\rm 2 + }} } \right] \cdot P_{{\rm CO}_{\rm 2} } \cdot \left[{{\rm H}^{\rm + } } \right]^{ - 2} = 7.97 \pm 0,04 \quad \left({I = 3{\rm M}} \right)} \\ {\Delta G{_f}{^0}{_{298,2}} = - 194,1_1 \pm 0,03_4 {{{\rm kcal}} \mathord{\left/ {\vphantom {{{\rm kcal}} {{\rm mol}}}} \right. \kern-\nulldelimiterspace} {{\rm mol}}}} \\ {{\rm MnHCO}_{\rm 3} ^ + :{\rm log}\left[{{\rm MnHCO}_{\rm 3} ^ + } \right]\left[{{\rm Mn}^{{\rm 2 + }} } \right]^{ - 1} \left[{{\rm HCO}_{\rm 3} ^ - } \right]^{ - 1} = 0,45 \pm 0,05\quad\left({I = 3{\rm M}} \right)} \\\end{array} $$\end{document}A predominance area diagram for the system Mn 2+ ‐H 2 ‐CO 2( g ) ‐H 2 S ( g ) including MnCO 3(ppt.) , α‐MnS and Mn 2+ is given.