Solubility constants and free enthalpies of metal sulphides,part 6: A new solubility cell

A solubility cell which can be operated continuously over the temperature range 5–95 °C has been developed. The solubility of Fe_0.88S (monoclinic pyrrhotite) in solutions $$S_0 = (H^ + ]) = H{\text{ }}m,{\text{ }}Na^ + ] = (1.00---H) m,{\text{ }}ClO_{4^ - } ] = 1.00 m)$$ at fixed partial pressures of H₂S has been investigated at 50.7 °C. The hydrogen ion concentration and the total concentration of iron(II) ion in equilibrium with the solid phase was determined by e.m.f. and analytical methods respectively. The data were consistent with $$\log ^* K_{pso} = \log \frac{{Fe^{2 + } ]pH_2 S}}{{H^ + ]^2 }} = 3.80 \pm {\text{ }}0.10{\text{ }}50.7^\circ C,{\text{ }}1 m(Na)ClO_4 ]$$ according to the overall reaction $$1.14{\text{ }}Fe_{0.88} S_{(s)} {\text{ }} + {\text{ }}2H_{(I = 1m)}^ + {\text{ }} \rightleftharpoons {\text{ }}Fe_{(I = 1m)}^{2 + } {\text{ }} + {\text{ H}}_{\text{2}} S_{(g)} {\text{ }} + {\text{ }}0.14{\text{ }}S_{(s)} $$