Why only 'freshly prepared' Fe2S04 is used for Ring test. Why can't old fe2so4 be used?

Asked by Artistic.Ivjyot | 6th Oct, 2011, 12:00: AM

Expert Answer:

Freshly prepared ferrous sulphate is used in brown ring test because FeSO4 upon exposure to air, oxidizes to form a corrosive brown-yellow coating of basic ferric sulphate, which is an adduct of ferric oxide and ferric sulphate and thus the brown ring will not be obtained. Oxygen in the air oxidizes iron (II) to iron (III) quite rapidly, in solution. Using a freshly prepared solution makes sure that the solutions contains iron (II) ions needed for the test and not iron (III) ions

12FeSO4 + 3O2 ? 4Fe2(SO4)3 + 2Fe2O3

Answered by  | 7th Oct, 2011, 09:55: AM

Queries asked on Sunday & after 7pm from Monday to Saturday will be answered after 12pm the next working day.