History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t3.61

v1.c13.s2.t3.61

*Rasa Ratna Samuccaya* has mentioned a number of processes for obtaining pure copper from chalcopyrite by smelting small charges in crucibles as reviewed by Jha (1990). He has conducted detailed experiments on the process of extraction of copper from chalcopyrite following the Ayurvedic route and using Lemon juice as the reductant. In this process after purification (sodhan) of chalcopyrite following the Ayurvedic process the ore mineral was roasted at 750-900°C adding lemon juice during the process. The process of roasting was alternated by tritaturation of the charge. In this process 100 c.c. of lemon juice was added per 100 gm of the ore. During the roasting process Cu and Fe get converted to citrates. The roasted ore was mixed with 25% Borax (flux) and more of lemon juice and the mixture was pressed into 20-30 mm balls. These balls were dried in Sun and then melted in Silimanite lined crucibles at 1250°C. There are four stages of the process of production. On carrying out the melting at 1250°C almost sulphide and gas free copper button separated from the liquid slag was obtained. *Fig. 8* shows the microstructure of the copper button showing dendrites of copper and some inclusions of CuS, CuO and slag.