Basic ferrous sulphate, FeSO4.FeO, is apparently obtained in solution when a 30 per cent, solution of ferrous sulphate is electrolysed between iron electrodes by a very weak current in the dark. After a few weeks the liquid becomes dark green in colour, but upon exposure to light it decomposes, depositing ferrous hydroxide in the absence of air.
The acid sulphate, FeSO4.5H2SO4.5H2O, is obtained when excess of sulphuric acid is added to a concentrated solution of ferrous sulphate. It yields iridescent crystals, with a brilliant lustre, but which are unstable, decomposing at 95° to 97° C. into the monohydrate. Thus: -
FeSO4.5H2SO4.5H2O = FeSO4.H2O + 5H2SO4.4H2O.
Other acid sulphates, namely 2FeO.3SO3.2H2O, FeO.2SO3.H2O, and FeO.4SO3.3H2O, have been described.
The following acid double sulphates have been prepared: -
2FeSO4.Cr2(SO4)3.H2SO4.2H2O,
2FeSO4.Al2(SO4)3.H2SO4,
2FeSO4.2ZnSO4.H2SO4,
2FeSO4.2ZnSO4.H2SO4, and
FeSO4.NiSO4.H2SO4. |