Study On Phase Equilibria And Physicochemical Properties In The Sub-ternary System Coming From The System Of Fe～(2+)-Mn～(2+)-Zn～(2+)-NH₄～+-SO₄～(2-)-H₂O At 298 K

In this paper, solubility phase equilibria were studied in the ternary systems of Me²+-NH₄⁺-SO₄²- -H₂O ( Me²+ is Mn²+, Zn²+, Fe²+), Mn²+-Zn²+-SO₄²--H₂O, Fe²+-Zn²+-SO₄²--H₂O and Fe²+-Mn²+-SO₄²--H₂O at 298 K by the isothermal method of equilibrium. The densities and value of pH of the saturated solutions in the systems of Zn²+-NH₄⁺-SO₄²-"-H₂O, Mn²+-NH₄⁺-SO₄²-^-H₂O, Fe²+-Zn²+-SO₄²-"-H₂O and Mn²+-Zn²+-SO₄²-^-H₂O also were determined. According to Ezrokhin equations, the densities and refractive indexes of the equilibrium liquid phase were calculated. The solubility phase diagrams and physicochemical properties curves were drawn.The solubility isothermal phase diagrams of the ternary systems of Me²+-NH₄⁺-SO₄²-^-H₂O consist of three invariant branches, two invariant points and three crystallization fields. Corresponding to three crystallization fields, there have three kinds of solid phase, such as MeSO₄.nH₂O, (NH₄)₂SO₁4 and (NH₄)₂Me(SO₄)₂.6H₂O,respectively. There are just two invariant branches, one invariant point and two crystallization fields of the solubility diagrams of the ternary systems of Fe²+-Mn²+-SO₄²-"-H₂O, Fe²+-Zn²+-SO₄²- -H₂O and Mn²+-Zn²+-SO₄²-^-H₂O, respectively. The only difference is the equilinria solid phase, ZnSO₄.7H₂O and MnSO₄.7H₂O in the system of Mn²+-Zn²+-SO₄²--H₂O, ZnSO₄.7H₂O and FeSO₄-7H₂O in the system of Fe²+-Zn²+-SO₄²-"-H₂O, FeSO₄-7H₂O and MnSO₄.5H₂O in the system of Mn²+-Zn²+-SO₄²--H₂O.At the eutectic point, because plenty of crystalloid nucleus form or lots of crystals dissolve suddenly, concentration of the saturation solution have a marked change. At the same time, the refractive indexes of crystals also have a sudden change because of new crystals forming or existence crystals dissolving. The values of pH change slowly in all systems. The calculated results of the densities and refractive indexes agree with that of the experimental results.