Changes in the standard Gibbs energies associated with the formation of double selenates (NH4)2M(SeO4)2.6H2O (M = Mn, Co, Ni or Zn) and (NH4)2Cd(SeO4)2.2H2O

Abstract

The energy changes associated with the formation of double selenates of the schoenite type were studied. By using the Filippov eutonic method, the ΔG° values were obtained directly for the formation of the (NH4)2M(SeO4)2.mH2O salts with M = Mn, Co, Ni, Zn and Cd and m = 6 except for Cd, for which m = 2. The ΔG° values are comparable with those for the analogous potassium salts and they lie within the range of –13.9 to –45.9 kJ mol-l. The fact that the final ΔG° value is primarily affected by the solubilities of the components and of the compound forming was verified for the examined (NH4)2SeO4-MIISeO4-H2O systems as well.