I am trying to obtain ferrous sulfate heptahydrate crystal from a liquor which is rich in Fe2+ and Fe3+ sulfate and sulfuric acid. However I can only achieve crystal (more likely powder) form of FeSO4.7H2O (37%) mixed with 58% Rhomboclase (H5O2)+Fe+++(SO4)2•2(H2O) with minor impurities. How can...