History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c37.12

c37.12

"The pounding or crushing was effected on a stone anvil with a hammer weighing eight or ten seers; when completely reduced to powder, the ore was made up into balls with cow-dung and roasted. The blast furnaces (Fig. 32) were prepared in the following manner. A quantity of common sand was spread on the door of a circular hut, in the centre of which a depression, 12 to 15 inches in diameter and 2 or 3 inches deep, was made; in this a layer of fine sand and another of ashes were laid to prevent the metal from adhering to the bottom of the receiver; two clay nozzles or tuyers were then placed on opposite sides of this hollow and a third between them, leaving the fourth side vacant for the slag to escape The nozzles were then connected by moist clay; and a circular rim of mud, a few inches in height, was raised, on which three annular vessels of fire-clay were placed to form the body of the furnace Each of these was 15 inches in external diameter, 10 inches high, and 3 inches thick. They were used repeatedly, but the lower part of the furnace had to be reconstructed for every charge. The bellows were simply goat-skins connected with the nozzles, and were worked by the families of the smelters. After a preliminary firing to dry the mud, the furnace was charged with charcoal, roasted ore and iron slag, the latter being employed as a flux. In a day of nine or ten hours' duration, 3 maunds of charcoal, 2½ of the roasted ore and 2 of the iron slag were consumed. The slag was drawn off, and the smelted copper, which had accumulated at the bottom of the furnace, was removed on the following day It was then remelted and refined in an open furnace under a strong blast from bellows,