Potassium SaltsA. 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.
SalicylatesA. 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.
SilicatesIn 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
Spread the Knowledge ⇩⇩⇩