Dissolve 40g of ferrous ammonium sulphate in a previously cooled mixture of 40 ml of sulphuric acid and 200ml of water,dilute with sufficient freshly boiled and cooled water to produce 1000ml .
Pipette accurately 25.0ml of the solution into a flask,add 2 drops of 1,10-phenanthroline solution and titrate with 0.1M ceric ammonium sulphate until red colour is changed to pale blue.Each ml of 0.1M ceric ammonium sulphate is equivalent to 0.03921g of Fe(NH4)2(SO4)2,6H2O .
The molarity factor of volumetric solution should not differ by more than ± 5% of the Prescribed strength and the molarity should be determined with a precision of 0.2%.
Restandardise after 15 days.
Storage in amper bottle with well fitted suitable stoppers which prevent access to atmospheric carbon dioxide.
Discard the solution after 30 days.
For storage and labeling follow the general procedure.