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Testing Procedure (Method of analysis) for Potassium Salts, Salicylates and Silicates


Learn how to determine the Potassium Salts, Salicylates and Silicates in Pharmaceutical substances.

Potassium Salts

A. Dissolve about 50 mg of the substance under examination in 1 ml of water or use 1 ml of the prescribed solution. Add 1 ml of dilute acetic acid and 1 ml of a freshly prepared 10 per cent w/v solution of sodium cobaltinitrite; a yellow or orange yellow precipitate is produced immediately.
B. Dissolve 0.1 g of the substance under examination in 2 ml of water or use 2 ml of the prescribed solution. Heat the solution with 1 ml of sodium carbonate solution; no precipitate is formed. Add 0.05 ml of sodium sulphide solution; no precipitate is formed. Cool in ice, add 2 ml of a 15 per cent w/v solution of tartaric acid and allow to stand; a white, crystalline precipitate is produced.
C. Ignite a few mg of the substance under examination, cool and dissolve in the minimum quantity of water. To this solution add 1 ml of platinic chloride solution in the presence of 1 ml of hydrochloric acid; a yellow, crystalline precipitate is produced which on ignition leaves a residue of potassium chloride and platinum.

Salicylates

A. To 1 ml of a 10 per cent w/v neutral solution add 0.5 ml of ferric chloride test solution; a violet colour is produced which persists after the addition of 0.1 ml of dilute acetic acid.
B. Dissolve 0.5 g of the substance under examination in 10 ml of water or use 10 ml of the prescribed solution. Add 0.5 ml of hydrochloric acid; the precipitate obtained after recrystallisation from hot water and drying at a pressure of 2 kPa melts at about 159°(2.4.21).
C. Dissolve 0.5 g ofthe substance under examination in 10 ml of water or use 10 ml of the prescribed solution. Add 2 ml of bromine solution; a cream-coloured precipitate is formed.

Silicates

In a lead or platinum crucible mix by means of a copper wire to obtain a thin slurry the prescribed quantity of the substance under examination with 10 mg of sodium fluoride and a few drops of sulphuric acid. Cover the crucible with a thin transparent plate of plastic under which a drop of water is suspended and warm gently; within a short time a white ring is formed around the drop of water.
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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