Platinum production in 1910 page 43



	PLATINUM AND ALLIED METALS. 779 metal intermediate in color between silver and tin. Its specific g ravity is 22.421 (Deville and Debray), and its fusion point is very high—2150° to 2250° C. At 1100° C. iridium begins to oxidize to a Eurple oxide. Tungsten has a higher melting point than iridium, ut oxidizes readily. Under ordinary conditions iridium is not attacked by any acid. Uses.—Owing to its unique qualities iridium finds an extensive use. Most of the metal produced is probably used for the purpose of hardening platinum, the percentage of iridium in the alloys ranging from 5 to 20 per cent. Up to 10 per cent the alloys are ductile and malleable; those containing from 10 to 20 per cent of iridium are hard and difficult to work; where the alloy contains 30 per cent of iridium it is no longer attacked by aqua regia.¹ Iridium is further used for various scientific and technical purposes, such as standard weights, pivots, contact points, and fountain-pen points. For certain high-temperature experiments (above 1600° C.) iridium is rolled in sheets and welded into tubes. Pure iridium is difficult to work on account of its brittleness. Iridium black, an oxide of the metal, is highly valued as a pigment for decorating chinaware. Production, import, and prices.—A few ounces of iridium are probably obtained from domestic crude platinum, but figures showing the quantity are not available. According to the Bureau of Statistics, 3,028 troy ounces of iridium and iridium in native combinations with platinum metals, valued at $140,232, or about $46.33 per troy ounce, were imported in 1910 into the United States. The price of iridium has been increasing rapidly. In 1909 the average price was about $35 per troy ounce; in 1910 the price rose still higher, and in October, 1910, iridium was quoted at $60 per ounce. The supply is evidently very limited. OSMIUM. Osmium is a hard and brittle bluish-gray metal, which, as stated above, generally occurs in combination with iridium. Its melting point is very high and its specific gravity is 22.48 (Joly and Vezes). Thus far little use has been found for it, except for certain kinds of incandescent lamps. In 1910, according to the Bureau of Statistics, 939 ounces of osmium, valued at $32,647, or about $33.70 per ounce troy, were imported into the United States. As in the case of iridium there is little present probability of obtaining a supply of osmium from domestic sources. PALLADIUM. Palladium is a white metal intermediate in color between platinum and silver. It is malleable, has about the hardness of platinum, and has a low specific gravity—11.97 (Violle). It has a lower melting point than any other of the platinum metals—about 1,549° C. Palladium finds a fairly large use in technology. Circles of astronomical instruments are made of it, and it is also employed in watchmaking. Its most extensive use is probably for certain alloys in dental work. It is also employed for soldering platinum metals. The demand for this metal is considerably greater than the supply. ' Molssan, H., op. cit., p. 899.