A System of Chemistry - 1809 Author:John Murray Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAP. II. SILVER. QILVER is in some measure connected with gold, both by its physical and chemical qualities. It is possessed' of great ductility and malle... more »ability, considerable lustre and specific gravity : it is with difficulty oxidized by the joint action of heat and air ) and its oxides, obtained by other processes, are like those of gold reduced by the action of heat alone. Not very abundant in nature, its Comparative scarcity adds to the value it derives from these qualiti s, and has rendered it the medium of exchange next in estimation to gold. Silver exists both native and mineralized, being combined with sulphur, oxygen, antimony, muriatic and sulphuric acids, forming a number of ores. Besides the proper ores of silver, there are also a number of metallic ores which contain this metal in small quantity, but' often sufficiently great to render the extraction of it profitable : such are the grey copper ore, several varieties of sulphuretted lead, and zinc, and some cobalt and arsenical ores. Silver is in general extracted without much difficulty. When native, it is separated from the earthy matter by washing, and amalgamation with mercury ; the latter being separated again by distillation. When alloyed with antimony, or arsenic, or when mineralized, the ore is ' roasted to expel these metals, the sulphur, or other volatile principles; and the residual matter is fused with lead,and refined by cupellation, in a manner similar to that which has been described under gold : the alloy of lead and silver being exposed to heat on the hearth of the refining furnace ; the lead being oxidized with the foreign metals, the oxidizement and vitrification of which it promotes ; and the vitrified oxide being in part absorbed, and in part driven off by the blast of the bellows. Th...« less