On the Kau·tilya's characterization tests for the purity of silver and its experimental replication

Development of characterization tests for ascertaining the purity of precious metals was an important task and skill in antiquity. The statement of Kau·tilya (Fourth century B.C.) on the characteristic features of pure silver is presented and discussed. According to Kau·tilya, if the cast silver pieces or ingots are of white colour like that of coagulated milk or curd, and have projections similar to a cock's comb on its surface, it should be considered as pure. It has been shown that the projections formed on the surface of cast pure silver are due to the evolution of dissolved oxygen during the solidification of the air-melted silver. The results of macro- and microscopic examinations of a cast pure silver surface are also presented, showing the observation made by Kau·tilya.