AcetatesA. Heat the substance under examination with an equal quantity of oxalic acid; acidic vapours with the characteristic odour of acetic acid are liberated.
B. Warm 1 g of the substance under examination with 1 ml of sulphuric acid and 3 ml of ethanol (95 per cent); ethyl acetate, recognisable by its odour, is evolved.
C. Dissolve about 30 mg of the substance under examination in 3 m1 of water or use 3 ml of the prescribed solution, add successively 0.25 m1 of lanthanum nitrate solution, 0.1 ml of 0.1 M iodine and 0.05 m1 of dilute ammonia solution. Heat carefully to boiling, within a few minutes a blue precipitate or a dark blue colour is produced.
Acetyl GroupsIn a test-tube (about 180 mm x 18 mm) place 10 to 20 mg or the prescribed quantity of the substance under examination and add 0.15 ml of phosphoric acid. Close the tube with a stopper through which passes a small test-tube (about 100 mm x 10 mm) containing water to act as a condenser. On the outside of the smaller tube, hang a drop of lanthanum nitrate solution.
Except for substances hydrolysable only with difficulty, place the apparatus in a water-bath for 5 minutes and remove the smaller tube. Mix the drop with 0.05 ml of 0.01 M iodine on a porcelain tile or glass slide and then add one drop of 2M ammonia at the edge of the mixed drop; after 1 or 2 minutes a blue colour is produced at the junction of the two drops and the colour intensifies and persists for a short time.
For substances hydrolysable only with difficulty, heat the mixture slowly to boiling point over an open flame instead of using a water bath.
AlkaloidsDissolve a few mg or the prescribed quantity of the substance under examination in 5 ml of water, add dilute hydrochloric acid until the solution has an acid reaction and then add 1 m1 of potassium iodobismuthate solution; an orange or orangered precipitate is formed immediately
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.
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