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Acetate of Lead

Acetate of lead should be completely soluble in distilled water, and when the lead is exactly precipi- chrome-red. (See No. 2706.) tated with dilute sulphuric acid, or by sulphu- 4106. Litharge. Litharge is an oxide retted hydrogen, the clear supernatant liquid of lead prepared by scraping off the dross that should be wholly volatilized by heat without forms on the surface of melted lead exposed residue. Sulphuric acid poured on acetate of to a current of air (dross of lead), and heating lead evolves acetic vapors. Acetate of lead it to a full red, to melt out any undecomposed is powerfully astringent. Take 4 pounds 2 metal. The fused oxide in cooling forms a ounces oxide of lead (litharge), acetic acid yellow or reddish semi-crystalline mass, which (specific gravity 1.048), and distilled water, of readily separates into scales; these, when each 4 pints; mix the fluids, add the oxide, ground, constitute the powdered litharge of dissolved by a gentle heat, strain, evaporate, commerce. Litharge is also prepared by exand crystallize. On the large scale it is usu- posing red lead to a heat sufficiently high to ally prepared by gradually sprinkling oxide of fuse it, and English litharge is obtained as a lead into strong vinegar, heated in a copper secondary product by liquefaction, from arboiler rendered negative-electric by having a gentiferous lead ore. The litharge of comlarge flat piece of leat soldered within it, constant stirring being employed until the acid is saturated, when the mother liquors of a former process may be added, the whole and paler colored. The dark color of the forheated to the boiling point, allowed to settle mer is chiefly owing to the presence of red till cold, decanted, evaporated to about the lead. In grinding litharge, about 1 pound of specific gravity 1.266 or 1.267, and then run olive oil is usually added to cach 1 cwt., to into salt-glazed stoneware vessels to crystal- prevent dust. Litharge is employed in pharlize. The best proportions are, finely pow-macy, to make plasters and several other dered litharge 13 parts, and acetic acid speci- preparations of lead; by painters as a dryer fic gravity 1.0482 to 1.0484, 23 parts. These for oils, and for various other purposes in the ingredients should produce about 38 parts of arts. merce is distinguished by its color into litharge of gold, which is dark colored and impure, and litharge of silver, which is purer, crystallized sugar of lead. A very slight ex- 4107. Nitrate of Lead. Litharge, 4½ cess of acid should be preserved in the liquid ounces; diluted nitric acid, 1 pint; dissolve during the boiling and crystallization, to pre- by a gentle heat, and set the solution aside to vent the formation of any basic acetate, crystallize. Employed as external application in cutaneous affections, &c. A very weak so- pint water, in a porcelain capsule, and when lution is an excellent remedy for chapped hands, &c. 4108. Tests for the Presence of Lead in its Solutions. The presence of lead in solutions may be recognized by the effects produced by the following reagents: gas ceases to be evolved, boil for 10 minutes, filter through muslin, and evaporate to dryness; next dissolve it in 1 pint water, agitate this solution frequently during 6 hours with ounce prepared chalk, and filter it; add to the filtered solution 1 fluid drachm each com-

The addition of sulphuretted hydrogen, mercial nitric acid and dilute sulphuric acid; hydrosulphuret of ammonia, or the alkaline evaporate the mixture until a pellicle forms sulphurets, to a solution containing lead, give on the surface, and set it aside to crystallize; fblack precipitates, insoluble in cold dilute dry the crystals on bibulous paper without acids, alkalies, alkaline sulphurets, and cyanide heat, and preserve them in a bottle. The of potassium.

Caustic potassa or soda gives a white precipitate, scluble in excess of the precipitant. Ammonia throws down a white precipitate, insoluble in excess, from all the solutions of lead salts, except that of the acctate.

Dilute sulphuric acid, in excess, also solutions of the sulphates, give a white precipitate, insoluble in dilute nitric acid, but soluble in a solution of potassa.

Chromate of potassa gives a yellow precipitate, whose soluble qualities are the same as that from sulphuric acid last mentioned. mother liquor will yield more crystals by further evaporation. This substance is als known as white vitriol.