Silver Producing large pro ducer of silver is the Broken Hill Proprietary Co., of New South Wales, Australia. The once famous Comstock lode mines in Nevada, which produced ore carrying values of two parts gold to three parts silver, are now unimportant, and probably the largest individual silver producer in the United States is the Amalgamated Copper Co., the silver being a by-product of its mines at Butte, Mont. Leadville, Colo., is an import ant silver-producing camp, but the ores are now generally low-grade. Silver Cliff and Aspen, Colo., were noted for their output of high-grade silver ores. In Utah the mines at Park City, notably the Daly West, are large producers of silver, though the ores also contain gold, lead and copper. In Idaho the silver-lead mines of the Cceur d'Alene region produce in the aggre gate much silver. In Mexico the states of Chihuahua, Durango, Guanajuato and Hidalgo all contain important silver-gold or silver-lead mines. The mines of Guanajuato are estimated to have produced one-sixth of the silver of the world and the Valenciana has an established record of production of 300,000,000 ounces. In South America the once famous mines of Cerro de Pasco in Peru are to be worked again by a New York company, but chiefly for copper. The silver output of the Cerro de Pasco mines from their discovery in 1630 up to 1886 is estimated at 462,250,000 ounces. In Ontario, Canada, the Cobalt District is one of the world's leading silver camps. In Europe, Germany is the most important silver-producing country, the metal coming from the Manusfield copper mines, the silver-lead mines at Mechevnich and the mines of the upper and lower Harz.
The world's production of silver in 1908 amounted to 203,186,370 troy ounces, valued at $108,684,400. Mexico that year led the world in silver production, and Mexico and the United States together produced nearly 70 per cent of the total output. Estimates based on the most
reliable information gave the world production of silver for the calendar year, 1917, by coun tries, as follows: With the exception of the years 1895 and 1902 when Mexico first led, the United States led the world in silver production for over 30 years up to 1902. Of the continents North America is easily first, with Europe now second.
The output of the chief silver-producing States of the Union in 1917, according to re liable authorities, was approximately as follows: Uses of Silver.— Silver is used for coinage and for ornamental articles, while the chloride, bromide and iodide of silver are of great im portance from their use in photography. Ar ticles plated with silver are in common use, as the cost of plating is small if the film of silver deposited is thin. A solution of the double salt potassium silver chloride(KCN.AgCN) is used, from which the silver is readily deposited. The articles to be plated are thoroughly cleaned, at tached to the negative pole of an electrical cir cuit of low voltage and immersed in the bath, • a silver plate being attached to the positive pole. The silver as deposited has a dead surface but is made bright by burnishing after removal from the bath.
In photography silver chloride in a layer of albumen or gelatine is used on the ordinary printing papers; various organic compounds are formed which are changed on exposure to light, and this change is shown by the action of cer tain reducing agents, developers, the resulting image being formed of unknown silver salts sus pended in the gelatine. In bromide prints which are more durable, the image is due to finely divided metallic silver. In the ordinary photo graphic dry plates, silver bromide or iodide is used in a gelatine film, as these salts are more easily affected by light. See BIMETALLISM;