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Acids. — Acidum Benzoicum.

PART III.

application to warts and corns, which it seldom fails to re-move ; but in applying it care must be taken to avoid erodingthe surrounding skin.

Officinal preparation. Acidum aceticum camphoratum, E. D.

ACIDUM BENZOICUM, Lond. Benzoic Acid.

" Take of benzoin, a pound and a half; lime fresh burnt,four ounces ; water, a gallon and a half; muriatic acid, fourfluid ounces. Rub the benzoin with the lime; then boil themin a gallon of water for half an hour, constantly stirring witha spatula, and pour off the liquor when it is cold. Boil whatremains in four pints of water, and pour off the liquor as be-fore. Afterwards mix the liquors together, and boil them toone half; then filter them through paper, and gradually dropin the muriatic acid until no more precipitation takes place.Finally, having poured off' the liquor, dry the powder in agentle heat: then put it into a proper vessel placed in a sand-bath ; and with a moderate fire sublime the benzoic acid."

Edinburgh.

" Take of benzoin, twenty four ounces ; subcarbonate of soda,eight ounces; water, sixteen pounds. Triturate the balsam withthe subcarbonate; then boil them in the water for half anhour, stirring them constantly, and strain. Boil the residue ofthe balsam in other six pounds of water, and strain. Mix thestrained liquors, and evaporate to two pounds; filter again,and drop in diluted sulphuric acid as long as any precipitationis produced.

" Dissolve the precipitated benzoic acid in boiling water:strain the liquor whilst it is hot through linen, and set it asideto crystallize. Wash the collected crystals with cold water;then dry, and preserve them for use."

Dublin.

" Take of benzoin, any quantity. Liquefy it in a wide-necked retort, to which a receiver is adapted but not luted,and sublime. The sublimed matter must be now and thenremoved from the tube of the retort, lest it accumulate intoo great quantity. If it be soiled with oil, press it betweenfolds of blotting paper to separate the oil, and repeat thesublimation."

8&n. Aeidc Benzoi'que (F.), Benzoesaure (G.), Acido Benzoico (/.).

The process of the Dublin College is the method recom-mended by Chaptal of separating the acid which the benzoincontains: but although the quantity contained be greater, yetif the fire be not very nicely regulated, a portion of empyreu-matic oil is also volatilized, which gives the acid a brown tinge,and cannot easily be entirely separated from it.' The London

• This acid was originally obtained by sublimation. It was described under thename of flowers of benvinby Blaise dc Vigencve, in 1608. Thomson'* Chemistry,4tl> edit. L'89.