This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Lac, Stick-Lac, improperly called Gum-Lac: a concrete brittle subslance, of a dark red colour; brought from the East Indies incrustated on pieces of slicks; internally divided into several cells; faid to be the resinous juice of certain trees, collected by winged red infects of the ant kind, impregnated with the tinging matter of the infects, and by them depofited either on the branches of the trees, or on sticks fattened in the earth for that purpose. In the cells are often observed small red bodies, which appear to be the young insects(a).
* A curious account by Mr. Kerr of the infect producing this gum, is contained in the Philos. Trans. vol. lxxi. part ii. From this it appears, that these infects are inhabitants of four trees; the sicus religiosa Linn, the Sicus Indica Linn, the Plaso Hort. Malabar, and the Rbamnus Jujuba Linn. The lac is however rarely found upon this last, and of an inferiour quality. The two species of Sicus yield a milky juice when wounded, which instantly coagulates into a vif-cid subitance. The Plaso tree by incifion gives out a red gum very similar to the lac. Hence the infect seems to have little trouble in anima-lizing the juices of these trees so as to make its cell, which is the (lick-lac. it is found in very great quantities on the uncultivated mountains on both sides the Ganges; and is of great use to the natives in various works of art, as varnish, painting, dying, etc.
The tinging red animal matter of the stick-lac dissolves both in water and in rectified spirit, and appears to be of the same general nature with that of cochineal; like which it is made dull by alkalies, and brighter by acids, and turned to a scarlet by solution of tin. If the lac be broken in small pieces, or grains, and infu-sed in warm water, till it ceases to give any tincture to the liquor; the remainder appears of a transparent yellowish or brownish colour, and, on raising the heat so as to make the water boil, melts and rises to the surface. The grains, or the plates formed from them by liquefaction, thus robbed of great part of the animal tincture, seem to be of an intermediate nature between that of wax and resins, or to partake of the na -ture of both: they crumble on chewing, and do not soften or stick together again: laid' on a red-hot iron, they instantly catch fire, and quickly burn off, with a strong and not disagree-able smell: distilled, they yield, like wax, an acid spirit and a butyraceous oik alkaline lixivia, and volatile alkaline spirits, dissolve them into a purplish liquor: they dissolve also, by the assistance of heat, in rectified spirit of wine, and communicate to it a yellowith or brownish red colour, an agreeable smell, and a bitterish, sub-astringent, not unpleasant taste. The lac in substance, whether entire, or freed from so much of its colouring matter as boiling water is capable of extracting, has no manifest taste or smell. . A spirituous tincture of stick-lac has been sometimes given as a mild restringent and corroborant in female weaknesses, and in rheumatic and scorbutic disorders. But the principal medicinal use of this concrete is as a topical corroborant and antiseptic, in laxities and scorbutic bleedings and exulcerations of the gums: some employ for this purpose a tincture of the lac in alum water; others, a tincture made in vinous spirits impregnated with the pungent antiscorbutics.
(a) See the emoires de I'acad. roy. desscienas de Pat is, pour l,ann. 1714.
Seed lac of the fhops.
Shell lac of the fhops.