Sodii Benzoas, B.P. Sodium Benzoate.
C7H5O2Na = 144.04.
Sodium benzoate, C6H5COONa, may be prepared by neutralising benzoic acid with solution of sodium carbonate, and crystallising, or carefully evaporating the solution to dryness. It is also official in the U.S.P. Sodium benzoate occurs as a white, amorphous, granular or crystalline powder, odourless or having a faint odour of benzoin, and a sweetish, astringent taste. It should contain about 98 per cent. (U.S.P., 99 per cent.). of sodium benzoate. Sodium benzoate rarely attains the official standard, as it is very difficult to dry it completely, and the commercial salt contains on an average 4 per cent. of moisture.
Soluble in water (1 in 2), alcohol (1 in 24).
Action and Uses.—Sodium benzoate has the action of benzoic acid, but is less irritating and is also preferred on account of its ready solubility in water (see Acidum Benzoicum). It is sometimes employed as an expectorant, but is used principally as an antiseptic in cystitis, and to render the urine more acid. It is converted by the kidney into hippuric acid, and is excreted as such. It is usually administered in mixture form and may also be dispensed in cachets. It is Incompatible with mineral acids and with ferric salts.
Dose.—1/4 to 2 grammes (5 to 30 grains).