Lac and its decolourization by orpiment as traced to babylon
Lākṣā in Sanskrit is a loan word and to the ordinary man non-connotative. It first occurs in Atharvaveda or about 15000 B.C. Pāṇini prefers to call lac Jatu, a genuine Sanskrit word signifying an adhesive. Lac applied to an abject in turnery would be lacquer and was called Jatuṣa. This would be shellac or purified lac. Crude lac contains two pigments. The lac resin, the secretion of the lac insect, contains a yellow pigment erythrolaccin. When only this pigment is allowed to remain the purified lac or shellac is coloured light yellow. But the inset body contains a red dye, laccaic acid, which remains incorporated in insect skins. Granules of crushed lac often show adhering residual skin particles. When such lac granules are melted the dye passes into melted lac as contamination and the resultant shellac appears chestnut coloured, But when orpiment is mixed with the lac granules and melted, the red dye is decolourized, and not the yellow erythrolaccin. The shellac then appears yellow, It means shellac is decolourized by orpiment when the contaminated red lac dye is destroyed.
Indian Journal of History of Science, Vol. 21, no. 2, (1986) 187–192.