Ferrous Sulphate or Green vitriol (FeSO4 7H2O)


It is obtained by dissolving Fe, FeO or FeCO3 in dil. H2SO4 the FeSO4 solution on crystallization gives light green crystals of FeSO4. 7H2O.

Fe + H2SO4                →             FeSO4+H2

FeO + H2SO4              →            FeSO4+H2O

FeCO3 + H2SO4             →         FeSO4 + H2O + CO3

FeSO4 (aq)      crystallization    →      FeSO4 7H2O

Green Uitrial



1. It is light Green colored crystalline solid highly soluble in water.

2. It is an efflorescent compound and when exposed in air for long time is oxidized to give brown color of ferric salt.

4FeSO4 + O2 + 2H2O            →              4Fe(OH)SO4

Basic Ferric Sulphate

(Brown in water)

3. Action of Heat :-

On heating, it gives anhydrous FeSO4 which is white in color.

FeSO4. 7H2O            →              FeSO4

Green                                      White.

Anhydrous FeSO4 on Further heating decompose forming Fe2O3 Ferric oxide (brown)

2FeSO4                    →                Fe2O3 + SO2 + SO3

White                                      Brown.


4. Action of Nitric oxide:-

FeSO4 solution absorbs nitric oxide forming a brown coloured complex of nitrosoferrous sulphate.

FeSO4 + NO                  →         FeSO4NO

Nitroso Ferrous Sulphate (Ring test).


5. Action of potassium Ferrec cyanide:-

With potassium fericyanide, it gives a deep blue coloured ppt of ferro ferricyanide commonly known as turn- bull’s ppt which is used for making blue coloured ink as blue pigment.

FeSO4 + K3 [Fe (CN) 6]            →          Fe3 [Fe(CN)6]2 + K2SO4


(Turn-bull’s ppt)

6. Hydrolysis:-

It is soluble in water and gets hydrolyzed to give acidic salt solution as it is salt of strong acid and weak base.

FesSO4 + 2H2O                       →            Fe (OH)2 +H2SO4

Weak base strong acid.


7. Reaction with K2Cr2O7 and KMno4 in acidic medium:-

FeSO4 is a reducing agent and in acidic medium if reduce KMNo4 and K2 Cr2 O7

10 FeSO4 + 8H2SO4 + 2KMNO4          →          5Fe2 (SO4)3 + 2MNSO4+K2SO4+8H2O

Pink                                                                 colorless


6 FeSO4 + 7H2SO4 + 2K2Cr2O7              →        3Fe2 (SO4)3 +Cr2 (SO4)3+ K2SO4+7H2O

Orange                                                            green



  • It is used as reducing agent.
  • It is used in medicine.
  • It is used as modant in dye.
  • It is used in mfg of ink.
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