Chap. II.

Acids.

327

Repeat the decoction, with other six pounds of water, andstrain. Mix these decoctions, and evaporate, until twopounds remain. Filter anew, and drop into the fluid, aslong as it produces any precipitation,Diluted sulphuric acid.Dissolve the precipitated benzoic acid in boiling water, strainthe boiling solution through linen, and set it aside to crys-tallize. Wash the crystals with cold water, dry and pre-serve them.

Dub.

Take of

Benzoin, any quantity.

Liquefy it in a retort with a wide throat, having a receiverfitted to it, but not luted, and sublime. Remove the sub-limed matter occasionally from the neck of the retort, lestit accumulate in too great a quantity. If it be soiled withoil, press it, folded up in blotting paper, and repeat the sub-limation.

Lond.

Take of

Benzoin, one pound and a half;Fresh lime, four ounces;Water, a gallon and a half;'•Muriatic acid, four fluidounces.

Triturate the benzoin with the lime, then boil for half anhour in a gallon of the water, stirring it assiduously witha spatula, and decant the liquor when cold. Boil the resi-duum again in four pints of water, and decant the liquoras before : then boil down the liquors mixed together toone half; filter through paper, and gradually drop in themuriatic acid, until there be no more precipitate.

Lastly, having poured off the liquor, dry the powder with agentle heat, put it in a proper vessel, placed in a sand bath,and sublime the benzoic acid with a gentle heat.

The distinguishing character of balsams is their contain-ing benzoic acid, which may be separated from the resin,their other principal constituent, either by simple solution inwater, sublimation, or by combining it with a salifiable base.The Dublin college directs if to be done in the second way.But, even with the greatest care, it is almost impossible to ma-nage the heat so as not to decompose part of the resin, andthus give rise to the formation of an empyreumatic oil, which

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