Quininae Hydrobromidum. Quinine Hydrobromide.
C20H25N2O2Br, H2O = 4.23.156.
Quinine hydrobromide, C20H24N2O2, HBr, H2O, maybe prepared by double decomposition of quinine sulphate and barium bromide, 100 of quinine sulphate being dissolved in 800 of water by heating to boiling, and a solution of 38 of crystallised barium bromide in 250 of water added in small portions at a time, with stirring. The whole is boiled for a short time and then allowed to cool. It should be tested for the presence of barium, and sufficient aqueous solution of quinine sulphate added if necessary. It is then filtered, evaporated at 60°, and allowed to crystallise in the cold. The crystals after draining on filter paper are carefully dried. It may also be prepared by neutralising diluted hydrobromic acid with quinine. The salt contains 76.6 per cent. of anhydrous quinine and 4.25 per cent. of water of crystallisation. It is official in the U.S.P. Quinine hydrobromide occurs in the form of light, white, silky, acicular odourless crystals, having a bitter taste, and is efflorescent. The aqueous solution is neutral, or very slightly alkaline, and is non-fluorescent. The sulphuric acid solution is fluorescent. Heated to 100° it loses its water of crystallisation, 4.25 per cent., equivalent to one molecule of water; at 150° it begins to melt, forming a syrupy liquid at 200°, On incineration, it leaves no residue. It gives the thalleioquin reaction. It should not give more than a faintly yellow colouration with concentrated sulphuric acid (absence of readily carbonisable impurities), nor produce a red colouration with nitric acid (difference from morphine and brucine). It should not contain more than traces of other cinchona alkaloids, nor of sulphates, and it should not give any precipitate with diluted sulphuric acid (absence of barium salt). In order to detect the presence of other cinchona alkaloids, dry 3 grammes of the salt at 50° for two hours, and then dissolve it in 30 mils of hot water, in an evaporating dish; next, add gradually, with constant stirring, 1.5 grammes of crystallised sodium sulphate, and evaporate to dryness. The dried residue, which should be neutral, is placed in a dry test-tube along with 30 mils of water and examined for other cinchona alkaloids as described under Quininae Sulphas.
Soluble in water (about 1 in 55), boiling water (1 in 1), alcohol (1 in 0.7), chloroform (1 in 10), or glycerin.
Action and Uses.—The amount of hydrobromic acid present in this salt is insufficient to produce any bromide action. Given with a medicinal dose of hydrobromic acid, quinine is found to produce symptoms of quinism less often, and the sedative action of the mixture is useful in neuralgia and acute rheumatism.
Dose.—½ to 6 decigrams (1 to in grains).