Silver
This metal is found native and in combination with sulphur, as the sulphides of lead, antimony, and copper; native silver occurs in fibrous or crystalline masses. The metal is obtained from the sulphuret by mixing the crushed ore with salt and roasting it, by which means it is converted into a chloride which, together with water, iron scraps, and mercury, is revolved in a large barrel. By this process the chlorine is removed by the iron and the mercury amalgamates with the silver, from which it is subsequently freed by distillation. Silver is freed from lead by melting the alloy and cooling slowly; the lead then solidifies in crystals, leaving the almost pure silver. The process of cupellation in shallow porous vessels made from bone-ashes gives a still greater degree of refining. Being melted with access of air, the lead oxidizes; the oxide or litharge melts, and, being absorbed by the cupel, the silver is left pure. Silver is the whitest of all metals, of high metallic lustre, is very ductile and tenacious, may be hammered to the ten-thousandth of an inch thick, and one grain may be drawn into four hundred feet of wire. Polished, it is an excellent reflector of light, and it is a good conductor of heat and electricity. To give silver the requisite hardness for coin and silver-plate, it is usually alloyed with about one tenth of its weight of copper. The specific gravity of silver is 10.5, and it is harder than gold, but softer than copper. See AMALGAMATION; MERCURY METALS.