Ferrous Sulphate Heptahydrate Molecular formula : FeSO4·7H2O Molar Mass : 278. 05 g/mol (heptahydrate) Appearance : blue/green or white crystals Destiny : 1.898 g/cm3 Melting point : 64°C Boiling Point: 90°C (becomes FeSO4·H2O) Ferrous Sulphate Monohydrate Properties:FeSO4.H2O Standard: HG2917-1999 FeSO4 % ≥90.0% Fe % ≥30.0% Pb % ≤ 0.002% As % ≤0.0002%