History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c37.67

c37.67

It has already been stated that a considerable amount of gold is lost during the processes of cleaning and colouring the ornaments. The waste liquor after these treatments, known as *jamak*, is sold to the *jamakwalas*. Gold is recovered from the *jamak* by the *jamakwalas* by a process, briefly described below. The waste liquor or *jamak* is boiled in an earthen vessel to reduce the volume. When practically the whole amount of water has been evaporated off, the viscous mass is removed to an open earthen vessel. This is then mixed thoroughly with a small quantity of borax and a large quantity of a substance, known as *poonoor* (a mixture of partially oxidized lead, copper and zinc with traces of silver and iron). The mixture is made into balls of about 2–3 inches in diameter with the addition of sufficient cow-dung. The balls are then dried perfectly in the sun, or over fire. Poonoor is a by-product, obtained during the purification of silver when alloyed with copper and other metals. For this purpose, the alloy of silver is mixed up with a large quantity of lead, and the mixture is melted on a small hearth; air is then blown over the molten mass, when the pure silver separates and collects at the bottom. The partially oxidized lead, together with impurities originally present in the silver, constitutes what is known as *poonoor* This operation for the purification of silver resembles practically that of cupellation.