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Testing Procedure (Method of analysis) for Ferric salts, Ferrous Salts and Iodides


Learn how to identify Ferric salts, Ferrous Salts and Iodides in Pharmaceutical ingredients.

Ferric salts

A. Dissolve a quantity of the substance under examination containing about 10 mg of iron in 1 ml of water or use 1 ml of the prescribed solution. Add 1 ml of potassium ferrocyanide solution; an intense blue precipitate, insoluble in dilute hydrochloric acid, is produced.
B. To 3 ml of solution containing about 0.1 mg of iron or to 3 ml of the prescribed solution add 1 ml of 2 M hydrochloric acid and 1 ml of ammonium thiocyanate solution; the solution becomes blood-red in colour. Take two portions, each of] ml, of the mixture. To one portion add 5 ml of ether, shake and allow to stand; the ether layer is pink. To the other portion add 3 ml of 0.2 M mercuric chloride; the red colour disappears.
C. To 2 ml of solution containing about 0.1 mg of iron or to 3 ml of the prescribed solution add acetic acid until the solution is strongly acidic. Add 2 ml of a 0.2 per cent w/v solution of 8-hydroxy-7-iodoquinoline-5-sulphonic acid; a stable green colour is produced.


Ferrous Salts

A. Dissolve a quantity of the substance under examination containing about 10 mg of iron in 2 ml of water or use 2 ml of the prescribed solution. Add 2 ml of dilute sulphuric acid and 1 ml of a 0.1 per cent w/v solution of 1,10-phenanthroline; an intense red colour which is discharged by addition of a slight excess of 0.1 M ceric ammonium sulphate is produced.
B. To 1 ml of a solution containing not less than 1mg of iron or to 1 ml of the prescribed solution add 1 ml of potassium ferricyanide solution; a dark blue precipitate is formed that is insoluble in dilute hydrochloric acid and is decomposed by sodium hydroxide solution.
C. To 1 ml of a solution containing not less than 1mg of iron or to 1 ml of the prescribed solution add 1 ml of potassium ferrocyanide solution; a white precipitate is formed which rapidly becomes blue and is insoluble in dilute hydrochloric acid.

Iodides

A. Dissolve a quantity of the substance under examination containing about 4 mg of iodide ion in 2 ml of water or use 2 ml of the prescribed solution. Acidify with dilute nitric acid and add 0.5 ml of silver nitrate solution. Shake and allow to stand; a curdy, pale yellow precipitate is formed. Centrifuge and wash the precipitate rapidly with three quantities, each of 1 ml, of water, in subdued light. Suspend the precipitate in 2 ml of water and add 1.5 ml of 10 M ammonia; the precipitate does not dissolve.
B. To 0.2 ml of solution of the substance under examination containing about 5 mg of iodide ion per ml or to 0.2 ml of the prescribed solution add 0.5 ml of 1 M sulphuric acid, 0.15 ml of potassium dichromate solution, 2 ml of water and 2 ml of chloroform shake for few seconds and allow to stand; the chloroform layer is violet or violet-red.
C. To I ml of a solution of the substance under examination containing about 5 mg of iodide ion add 0.5 ml of mercuric chloride solution; a dark red precipitate is formed which is slightly soluble in an excess of this reagent and very soluble in an excess of potassium iodide solution.
Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
Email: .moc.enilediugamrahp@ofni Need Help: Ask Question


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