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By James M. Hill.
In discussing the uses of platinum in war it is not practicable to confine the discussion to that metal alone, for several metals of the platinum group are useful in war and must be considered together. These metals are platinum, iridium, palladium, rhodium, osmium, and ruthenium. The first four named are of commercial and military value; the last two are, "so far as known, of little commercial value. The natural alloy of osmium and iridium, that is called osmiridium or iridosmine, is used commercially in a small way.
Pure platinum is required by the Government in very large quan­tities for use in the "contact process" of making sulphuric acid and for use at the new plants erected for the fixation of nitrogen. It is needed also for making utensils and apparatus at a great number of chemical laboratories, which control our whole industry. Finally, large quantities of platinum and iridium are required for all kinds of electrical equipment.
The so-called platinum used in electrical work is an alloy of platinum and iridium, and the alloy used for some work may carry as high as 50 per cent of iridium. Each telephone and telegraph instrument has platinum contacts; every high-grade magneto for an airplane, auto­mobile, motor boat, or gas engine has from two to six contacts of plati­num; and the multitude of contacts on telephone switchboards and the relay instruments of both telephone and telegraph lines are of platinum. For some purposes in electrical work satisfactory sub­stitutes for piatmum have been found and are being used; for other purposes substitutes will probably soon be used; but for many high-duty electrical contacts no satisfactory substitutes have yet been found. Pure iridium is apparently of little commercial use. It is em-ed principally as a hardening element in the platinum-iridium alloys used in the electrical industry and by jewelers. Jeweler's platinum contains an average of 10 per cent of iridium, though some alloys that run as high as 15 per cent of iridium are used for certain work. Therefore, every 100 ounces of piatmum used in the jewelry trade contains 10 ounces of iridium, to produce which it is necessary to obtain and refine approximately 200 ounces of Russian or 630 ounces of Colombian crude platinum. The alloys used in the elec­trical industry contain from 15 to 50 per cent of iridium, and the average alloy used in electrical work doubtless contains 20 per cent of iridium. To obtain 100 ounces of electrical platinum it is therefore necessary to refine 400 ounces of Russian or 1,260 ounces of Colom­bian crude platinum.