Of the total world silver production over 80 per cent. comes from the mines of the Western Hemisphere. For many years Mexico was the leading silver-producing country of the world, but the unsettled political conditions have so interfered with mining operations that the production for 1917 was less than a half of that for 1911 or 1912. The United States, a close second to Mexico in pre-revolutionary years, now occupies the leading position. Canada and Central and South American countries also produce important quantities of silver. In the Eastern Hemisphere, Australia is the leading silver producer. Smaller amounts are contributed by Spain, Austria, Turkey, India, and Japan.
Changes in practice of silver recovery and even silver prices have little influence on silver production. It will be stimulated rather by discoveries of new silver deposits or by enlarged and improved base-metal milling operations.
The principal silver deposits of the world are controlled politically by the United States, Mexico, and Great Britain, the three nations controlling about 85 per cent. of the total production in 1913. United States capital controls the entire silver output of the United States, and mines producing half of the Mexican output, one-fourth of the Canadian output, and much of that of the Central and South American countries, in all something over one-half of the world’s normal silver production. Great Britain controls probably one-third of the world production, chiefly in Canada, Australia, India, Africa, and Mexico. German capital owns probably one-tenth, located partly in Germany but mainly in Mexico. The remaining silver deposits of the world are owned by Japanese, Spanish, and French capital. Ownership of reduction plants is not a powerful form of control in the case of silver. The United States owns about four-sevenths of the total smelting and refining capacity of the world, the remaining three-sevenths being controlled largely by German, British, and Mexican capital.
Although the greater part of the silver produced each year comes from North and South America, the world’s silver market is located in London because of the close relations between English business interests and India and China, the chief consumers of the metal.
The United States Government, however, will (1920) purchase all American silver offered at $1 per ounce, up to 207,000,000 ounces.
CHAPTER XXXI
PLATINUM
By James. M. Hill
USES OF PLATINUM
In past discussion of the uses of platinum some confusion has resulted from the lack of appreciation that all commercial platinum is not the pure metal. The pure metal is required for chemical work of all sorts, but for other uses the iridium alloys are used. Electrical platinum contains 15 to 50 per cent. iridium, but averages 25 per cent., and jeweler’s platinum carries about 10 per cent. iridium. Palladium, another of the platinum group metals, is also of importance, chiefly in the form of palladium-gold alloys, which can be used to replace platinum in the dental and jewelry industries. Rhodium, one of the rarer elements of crude platinum, has a limited use in electrical pyrometers. Osmium and ruthenium, the remaining members of the platinum group, appear to have little use, though osmium, when properly used, can be employed as a substitute of iridium to harden platinum alloys.
The essential uses of platinum metals are in the chemical and electrical industries, and probably the dental industry should be classed as essential. Pure platinum is required in the chemical industry for catalysers in the manufacture of sulphuric acid (about 75,000 ounces now in use in the United States) and in the manufacture of nitric acid from ammonia. For the sulphuric-acid industry, platinum chloride is the primary material containing platinum. Asbestos or anhydrous magnesium sulphate soaked in platinum chloride, and then baked to drive off the chlorine, forms what is known as “contact mass,” which is charged into the chambers of contact acid plants. Very fine-mesh platinum gauze is used for the catalyser in nitric-acid plants. Some gauze used for this purpose has a reinforcing edge of platinum-iridium wire. Pure platinum utensils of various kinds, including crucibles, dishes, tongs, and triangles, are required in every chemical laboratory. It is possible to substitute palladium-gold alloys, or even gold, nickel, nichrome, and silica, for some utensils, but no substitutes have yet been found which will entirely replace platinum chemical ware.
Platinum-iridium alloys have been used extensively by the electrical industry, but substitutes are constantly being developed. Tungsten, molybdenum, and nickel-chrome alloys are the principal substitutes used so far, but their use has not done away with the necessity of platinum in the industry. The principal use of platinum-iridium alloys in electrical work is in contact points, and the proportion of iridium necessary in the alloys is directly dependent on the intensity of the current passing through the contacts and the speed at which the contacts move. Probably the largest consumption of platinum alloy is in the manufacture of telephone and telegraph equipment, including sending and receiving instruments, switch boards and relays. There is also a large consumption of platinum for contacts in magnetos used for various kinds of internal-combustion engines. Automobile makers are, however, developing starting systems that do not require platinum, so we can hope for a lessening future demand from that quarter.