SUGAR OF LEAD, properly acetate of lead, is prepared by dissolving pure litharge, with heat, in strong vinegar, made of malt, wood, or wine, till the acid be saturated. A copper-boiler, rendered negatively electrical by soldering a strap of lead within it, is the best adapted to this process on the great scale. 325 parts of finely ground and sifted oxide of lead, require .575 parts of strong acetic acid, of specific gravity 7° Beaume, for neutraliza tion, and afford 960 parts of crystallized sugar of lead. The oxide should be gradually sprinkled into the moderately hot vinegar, with constant stirring, to prevent adhesion to the bottom; and when the proper quantity is dissolved, the solution may be weakened with some of the washings of a preceding process, to dilute the acetate, after which' the whole should be heated to the boiling point, and allowed to cool slowly, in or der to settle. The limpid solution is to be drawn off by a syphon, concentrated by boiling to the density of 82° B., tak ing care that there be always a faint ex cess of acid, to prevent the possibility of any basic salt being formed, which would interfere with the formation of regular crystals. Should the concentrated liquor be colored, it may be whitened by filtra tion through granular bone black.
Stoneware vessels, with salt glaze, an swer for crystallizer:. Their edges should be smeared with candle-grease, to pre vent the salt creeping over them by efflorescent vegetation. The crystals are drained, and dried in a stove-room very slightly heated. Linen, mats, wood, and
paper, imbued with sugar of lead, and strongly dried, readily take fire, and burn away like tinder. When the mother wa ters cease to afford good crystals, they should be decomposed by carbonate of soda, or by lime skilfully applied, when a carbonate or an oxide will be obtained, fit for treating with fresh vinegar. The supernatant acetate of soda may be em ployed for the extraction of pure acetic acid.
Acetate of lead is much used in calico printing. It is poisonous, and ought to be prepared and handled with attention to this circumstance.
There are two subacetates of lead; the first of which, the ter-suhacetate, has three atoms of base to one of acid, and is the substance long known by the name of ::::.oulard's extract. It may be obtained by digesting with heat a solution of the neutral acetate, upon pure litharge or massicot. The solution affords white crystalline scales, which do not taste so sweet as sugar of lead, dissolve in not less than 30 parts of water, are insoluble in alcohol, and have a decided alkaline re action upon test paper. Carbonic acid, transmitted through the solution, preci pitates the excess of the oxide of lead in the state of a carbonate, a process long ago prescribed by Thenard for making white-lead. This subacetate consists of 88.66 of oxide, and 13.34 acid, in 100 parts. It is employed for making the orange sub-chromate of lead, as also sometimes in surgery.