A. Dissolve about 20 mg of the substance under examination in 2 ml of water or use 2 ml of the prescribed solution, add about 0.5 ml of 2 M hydrochloric acid and about 0.5 ml of thioacetamide reagent; no precipitate is produced. Add drop wise 2M sodium hydroxide; a gelatinous white precipitate is produced which re-dissolves on addition of further 2M sodium hydroxide. Gradually add ammonium chloride solution; the gelatinous white precipitate appears.
B. Dissolve about 20 mg of the substance under examination in 5 ml of water or use 5 ml of the prescribed solution, add 5 drops of ammonium acetate solution and 5 drops of a 0.1 per cent w/v solution of mordant blue 3; an intense purple color is produced.
C. To a solution of the substance under examination in water add dilute ammonia solution until a faint precipitate is produced and then add 0.25 ml of a freshly prepared 0.05 per cent w/v solution of quinalizarin in a 1 percent w/v solution of sodium hydroxide. Heat to boiling, cool, and acidify with an excess of acetic acid, a reddish violet color is produced.
Amines, Primary Aromatic
Acidify the prescribed solution with 2 M hydrochloric acid or dissolve 0.1 g of the substance under examination in 2 ml of 0.1M hydrochloric acid and add 0.2 ml of sodium nitrite. After 1 or 2 minutes add the solution to 1ml of 1-naphthol solution; an intense orange or red color and, usually, a precipitate of the same color is produced.
A. Heat a few mg of the substance under examination with sodium hydroxide solution; ammonia is evolved, which is recognisable by its odor and by its action on moist red litmus paper, which turns blue.
B. To the prescribed solution add 0.2 g of light magnesium oxide. Pass a current of air through the mixture and direct the gas that is evolved to just beneath the surface of a mixture of 1 ml of 0.1 M hydrochloric acid and 0.05 ml of methyl red solution; the color of the solution changes to yellow. On addition of 1ml of a freshly prepared 10 per cent w/v solution of sodium cobaltinitrite, a yellow precipitate is produced.
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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