ACETATE OF LEAD.

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danger of absorption. In one case, related by Kopp (Richter, Ausfuhr .Arzneim. iv. 613) a child was destroyed by it.

Unguentum Plumbi Carbon at is, Ph . Dubl. and Ed. (Carbonateof lead, reduced to very fine powder, gij.; ointment of white wax, lbj. M.The Edinburgh formula is one part of carbonate of lead, and five partsof simple ointment.)—This ointment is valuable as a cooling and desiccativeapplication to excoriated surfaces or burns.

An ointment or plaster of carbonate of lead has been known to giverelief in some cases of neuralgia {Journ. de Pharm. xx. 603).

Plum'bi Ace'tas. — Ac'etate of Lead .

History. —Raymond Lully and Isaac Hollandus were acquainted withthis salt in the 13th century. It has been known by several appellations,as sugar of lead (saccharum saturni), acetated ceruse (cerussa acetata),and superacetate of lead (plumbi superacetas).

Preparation. —Though directions are given in the Pharmacopoeia for its preparation, it is never made by the apothecary, but is procuredfrom persons who manufacture it on a large scale.

It is sometimes made by immersing lead in acetic acid. The metalattracts oxygen from the air and combines with the acid. It may alsobe procured by dissolving carbonate of lead in acetic acid, filtering thesolution, and evaporating so that it may crystallize. But it is almostexclusively obtained now by dissolving oxide of lead (litharge or massicot)in acetic (pyroligneous) acid. This process is the one followed in theLondon Pharmacopoeia; where four pounds and two ounces of powderedlitharge are directed to be dissolved, by the aid of a gentle heat, in amixture of four pints of acetic acid and four pints of distilled water. Thesolution is to be strained, and evaporated so that it may yield crystals.In this process, the oxide, in virtue of its affinity for acetic acid, combineswith the latter, and forms a definite compound.

Properties. —The primary form of the crystals of this salt is the rightoblique-angled prism. Their taste is sweetish and astringent. In a dryand warm atmosphere they slightly effloresce. When heated they fuse,give out their water of crystallization, and, at a higher temperature,are decomposed; yielding acetic acid, pyroacetic spirit (or acetone),carbonic acid, inflammable gas, and water : the residuum is a mixture oflead and charcoal. Acetate of lead is soluble in both water and alcohol.The aqueous solution feebly reddens litmus, though it communicates agreen colour to the juice of violets. A solution of the neutral acetate ispartially decomposed by carbonic acid : a small quantity of carbonate oflead is precipitated, and a portion of acetic acid is set free, which protectsthe remaining solution from further change.

Characters. —When heated with sulphuric acid, the vapour of aceticacid is disengaged. Its solution is known to contain lead by the testsfor this metal already mentioned (vide p. 505). If a small quantity ofacetic acid be added to the solution, a current of carbonic acid occasionsno precipitate. The ordinary acetate of the shops usually throws downa scanty white precipitate (carbonate of lead) with carbonic acid. Whencharred, it readily yields globules of metallic lead on the application ofthe blowpipe flame.