The solubility of potassium ferrate(VI) (K2FeO4)
was measured in a mixture solution containing various molar ratios of
KOH and NaOH at a total concentration of 14 M from (10 to 60) °C. The
solubility of K2FeO4 decreased because of the presence of K+ in the solution mixture. The solubility (S*) was expressed as log S* = 5.830 − 2019/T − 5.845XK+0.5 + 1.595XK+ + 724XK+0.5/T (σ = 0.024), where XK+ is the mole fraction of K+ in the solution mixture and T is in Kelvin. A comparison of the values of S* in different alkali metal hydroxide solutions showed that the solubility of K2FeO4 was diminished in KOH and CsOH and similarly in LiOH and NaOH solutions. The solubility product constant (Ksp*), calculated from the solubility measurements, was given as log Ksp* = 18.10 − 6055/T − 17.535XK+0.5 + 4.785XK+ + 2171XK+0.5/T (σ = 0.061). The heat of dissolution (ΔHdiss) decreased linearly with an increase in the mole fraction of K+ ions. The significance of the solubility results is briefly discussed.
