Generally Ferrous Sulfate(Green Vitriol) heptahydrate is most widely used as an iron supplement for treating iron-deficiency anemia. The assay determines the amount of ferrous iron present in a given sample which is changed to Ferric form by oxidation.
Principle
The assay of Ferrous Sulphate is based on Oxidation Reduction Reaction where Ferrous ions (Fe²⁺) are oxidized to Ferric ions (Fe³⁺) by a strong oxidizing agent like potassium permanganate in acidic medium.So,In this method ,The given Sample of Ferrous Sulphate (FeSO₄·7H₂O) is titrated against the acidic medium of Potassium Permanganate (KMnO4) until a faint pink colour is obtained.
Reactions
2KMnO4+ 3H2SO4 —–>K2SO4+2MnSO4+3H2O+5 [O]
10FeSO4+5 H2SO4 +5 [O] ——>5Fe2 (SO4)3+ 5H2O
————————————————————————————–
10FeSO4+8 H2SO4 +2KMnO4——–> K2SO4+2MnSO4+8H2O+5Fe2 (SO4)3
1000ml of 1N Potassium Permanganate KMnO4 are equivalent to 278 gm of FeSO₄·7H₂O
Each ml of 1N FeSO₄·7H₂O are equivalent to 0.278 gm of FeSO₄·7H₂O
Procedure
An accurately 1gm weighed amount of Ferrous sulphate is dissolved in 25-30ml of distilled water ,further 20 ml of dilute sulphuric acid is added on it and the solution is titrated against the previously prepared solution of 0.1N Potaasium Permanganate solution until a faint pink colour is persist.
Alternative Method
As per I.P.-1985, the assay of Ferrous sulphate can be performed by using Cerric Ammnonium Sulphate 2(NH4)2Ce(SO4)3 as a titrant (oxidising agent) and Ferroin sulphate as an indicator.
*Ferroin sulphate is a solution of O-phenanthroline in aqueous solution of ferrous sulphate.
2FeSo4+2(NH4)2Ce (SO4)3—-àFe2 (SO4)3+ (NH4)2(SO4) + Ce2 (SO4)3
Procedure
Accurately weighed about 1 gm of Ferrous Sulphate of given sample and dissolve in a 30 ml of water further 20ml of dilute sulphuric acid is added to it and the resultant solution is titrated against with 0.1N ceric ammonium sulphate using indicator Ferroin sulphate.
Each ml of 0.1N Cerric Ammonium Sulphate are equivalent to 0.0278 gm of FeSO₄·7H₂O.
Uses-Ferrous Sulphate use as Haematinic, iron supplement, treatment of anaemias due to iron deficiency.