Assaying

Assaying, method of chemical analysis used to determine the presence, absence, or quantity of a particular component of ores or alloys, used since the 2nd millennium B.C. In modern assaying, the sample is fused with a flux containing lead oxide. This produces a lead button containing the material being sought (such as gold or silver), which is heated in oxygen to oxidize the lead and other impurities. This leaves a bead of the metal sought, which is then weighed.