Quininae Sulphas Acidus. Acid Quinine Sulphate.
C20H26N2O6S, 7H2O = 548.41.
Acid quinine sulphate (Quininae Bisulphas, U.S.P.; Quinine Bisulphate), C20H24N2O2, H2SO4, 7H2O, may be prepared by dissolving to of ordinary quinine sulphate in a mixture of 15 of water and 6.85 of diluted sulphuric acid (specific gravity, 1.110 to 1.114) on a water-bath at a temperature not exceeding 60°. The warm solution is filtered and allowed to cool; after standing for one day in the cold the acid quinine sulphate crystallises out and may be drained and dried over sulphuric acid at a temperature of 10° to 15°. The salt contains 59.12 per cent. of anhydrous quinine, 17.88 per cent. of sulphuric acid, and 22.99 per cent. of water of crystallisation. Acid quinine sulphate occurs in the form of transparent, odourless, colourless, or white, glistening, rhombic crystals, or small needles, having a very bitter taste, efflorescing in dry air, and turning yellow on exposure to light. The aqueous solution is strongly acid, shows a blue fluorescence, and gives the thalleioquin reaction. On hearing, the salt softens at 60°, becomes semi-fluid at 70°, and melts at about 160° with decomposition, being converted into acid quinicine sulphate, which forms with diluted sulphuric acid a yellow, but non-fluorescent solution. At 100° it loses all its water of crystallisation. On ignition the salt is slowly consumed without leaving any residue. With sulphuric acid not more than a faint yellow colouration is produced (limit of readily carbonisable impurities). It should be free from chlorides. The presence of other cinchona alkaloids should be tested for by dissolving 2 grammes of the salt, dried at 50° for two hours, in 20 mils of water, carefully neutralising with diluted solution of sodium hydroxide, evaporating to dryness, and completing the examination as described under Quininae Sulphas.
Soluble in water (1 in 10), alcohol (1 in 45).
Action and Uses.—This salt is much more soluble than ordinary quinine sulphate, and thus possesses similar advantages to other acid salts of quinine (see Quininae Hydrobromidum Acidum and Quininae Hydrochloridum Acidum). It is employed in the form of drops (1 in 150) in purulent ophthalmia, hypopyon, and ophthalmic diphtheria. It is incompatible with potassium iodide.
Dose.—½ to 6 decigrams (1 to 10 grains).