History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c22.4

c22.4

Take lead of the weight of 30 palas and rub it with the milky juice of *Calotropis gigantea* and calcine it till its weight is reduced to a *karsha*: this residue, even if it be calcined a thousand times, will not undergo further decay (i e. diminution in weight). Metallurgists call this residue derived from lead *chapala*. (This possibly refers to the extraction of silver from argentiferous lead by a process similar to cupellation.)