310. LACCA.—LAC. GUM-LAC. A resinous exudation from punctures, made by insects, in the bark of several East Indian trees, and also in plants growing in Arizona and other Western States. The twigs, with their deep reddish-brown incrustations, are called stick-lac. Seed-lac consists of the small, irregular fragments broken off from the twigs. Lump-lac is made by melting the stick-lac, and, after it has hardened, breaking the brown, translucent mass into lumps. Shell-lac or gum-shellac, the most common form, is prepared by spreading the melted lac out in thin layers, which, on drying, form thin, brittle sheets, glossy, more or less transparent, varying from amber to dark brown in color; in packing, these sheets are broken into fragments, in which form shellac is commonly met with in market; odorless and tasteless. Lac contains several resins, laccin (a peculiar principle insoluble in alcohol), and a coloring matter varying in quantity in the different forms; this coloring matter, "lac dye," is equal to cochineal dyes; it is soluble in water, being obtained from the washings in making the different forms of lac. Lac is not used medicinally, but is extensively employed in the arts for making varnishes and sealing-wax.
A Manual of Organic Materia Medica and Pharmacognosy, 1917, was written by Lucius E. Sayre, B.S. Ph. M.