Purifying ferrous sulfate

For my wood staining experiments I have purchased 1 kilo of ferrous sulphate as a source of iron(II). It turned to be quite oxidised (yellowish) and the its solution is muddy yellow instead of green. Does it make sense to try to recrystallise it in a hope that oxidation products are less soluble or insoluble in water?




You better make your turbid solution boil with some iron wires $\ce{Fe}$ and a bit of sulfuric acid. The turbidity observed in your solution is due to a mixture of two precipitates containing $\ce{Fe^{3+}}$ ions, produced by the oxidation reaction $$\ce{4 Fe^{2+} + O2 + H2O -> 4 [Fe(OH)]^{2+}}$$ then $$\ce{[Fe(OH)]^{2+} + 2 H2O -> Fe(OH)3(s) + 2H+}$$ or $$\ce{[Fe(OH)]^{2+} + SO4^{2-} -> Fe(OH)SO4}(s)$$ Whatever the chosen reaction, both are producing a turbid solution. And this turbid solution may be destroyed to produce $\ce{Fe^{2+}}$ ions if boiled with some iron wires or nails dipped into the acidified solution, which will reduce ferric substances into ferrous ions, according to : $$\ce{2 Fe(OH)3 + Fe + 6 H^+ -> 3 Fe^{2+} + 6 H2O}$$ or $$\ce{2 Fe(OH)SO4 + Fe + 2 H^+ -> 3 Fe^{2+} + 2 SO4^{2-} + 2 H2O}$$ In both cases, the precipitate has disappeared and all the iron in solution is under the form of ferrous ions $\ce{Fe^{2+}}$ and only these ions


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