Platinum is one of the most ductile of all known metals. It is so ductile that it can be drawn to the finest possible wire, then covered with a very thick coating of silver in wire form, then drawn again to infinitesimal fineness, the silver dissolved off, and this interior again coated with silver. So that one ounce of plati num wire could be made to stretch as great a distance as from New York to New Orleans, or from Buenos Aires across the Andes to the Pacific Ocean.
Although 99 per cent of the world's produc tion of platinum comes from Russia and Colom bia, small deposits of it have been found in many different parts of the earth. In the United States it occurs in Oregun, California, Wyoming, Washington, Nevada, Idaho, Ari zona, New Mexico, Utah and Colorado, and it has occasionally been met with in other States, a fine nugget containing 38.1 grams, or almost one and one-quarter ounces troy, having been found about 1880 in glacial drift near Platts burg, N. Y. It has also been mined in Ontario, Canada, as well as in British Columbia, and it is reported as occurring in Alaska. In Mexico and Honduras it has also been encountered. In South America, besides the important Co lombian deposits, platinum occurs in Brazil, and a little has been reported from Ecuador and French Guiana, and from San Domingo. Bor neo, Burma, Assam and Ava have also fur nished small quantities, and a trifle has been discovered in the Bengal Presidency and in Mysore, India. In Europe it occurs in Norway, in Finnish Lapland, in Westphalia and in the Harz Mountains, Germany, as well as in Tran sylvania, and a trifle has been found in County Wicklow, Ireland. Quite recently there have been discovered very promising deposits, cov ering a wide area, in the Ronda Mountains, province of Malaga, Spain. On the African con tinent platinum has been met with in Algeria, in the Kongo Free State and in Cape Colony, as well as in Griqualand. Finally, notable de posits occur in Queensland and in New South Wales, Australia, and some has been found in New Zealand and in Tasmania as well. The chief sources of platinum are alluvial deposits, wherein it usually occurs either in rounded grains, or in scales which have been worn down by the attrition of the river gravel: occa sionally, however, nuggets of quite considerable size are found. It is very commonly associated with gold, and usually with one or more of the different platinum metals, iridium, palladium, ruthenium, rhodium and osmium or the alloy iridosmium. It is opaque, with a metallic lus tre; the color and streak are light steel-gray, shading into silver-white. There is no recog nizable cleavage; the fracture is hackly. The hardness is fully four, and the specific gravity of native, unrefined platinum ranges from 14 to 19, this wide variation being due to the per centage of iron, or of palladium; ruthenium or rhodium that may be present; the specific gravity of refined platinum is 21.48-21.50. The
atomic weight is 195.21 (0=16). The co efficient of refraction was determined by Kundt to be 1.76 for red, 1.64 for white and 1.44 for blue, and Donde found, in reflected light, 2.06 for Na, 2.16 for red. The specific heat is 0.032+ and the coefficient of linear expansion about 0.0000049. Platinum is usually unaltered before the blowpipe. but it is readily fusible in the oxyhydrogen flame and in the electric arc, the melting point being about 1779° Centigrade, making it, after palladium, the most easily fusible of the platinum metals. It is not at tacked by either boracic or phosphoric acid, nor by oxygen even when it is at a red heat, and but very slightly by pure hydrochloric acid, nitric acid or sulphuric acid. It dissolves soon, however, if treated with the mixture of nitric and hydrochloric acid, known as "aqua regia," into platinum chloride, although an admixture of iridium or even of rhodium renders it some what more resistant. It forms alloys with gold and a number of other metals, the resultant alloy being • more fusible than pure platinum. On the other hand, it gains greatly in hardness when alloyed with iridium, the product, called platin-iridsum, being applied to a number of uses where hardness is especially to be desired. Chlorine, bromine and iodine attack it, and a mixture of bromine and hydrochloric acid works as actively as a dissolvent as does aqua regia. At a high temperature platinum com bines directly with sulphur, phosphorus and arsenic. Easily fusible alloys of it may be made with potassium and sodium. As there is little difference between the specific gravity of gold and platinum, the miners are not able to separate the metals by the simple method of washing in habitual use, and recourse is had to quicksilver, which by combining with the gold to the exclusion of the platinum renders it possible to extract the latter. The method of refining platinum used in the United States assay office in New York is stated by the super intendent, Hon. Verne M. Bovie, to be the fol lowing: In the electrolytic process of refining gold, platinum remains in solution in the gold chloride electrolyte, from which it is precipi tated by means of ammonium chloride. The precipitate is then well washed and reduced at a red heat to a metallic platinum sponge. naturally contains impunties, and is, therefore, redissolved in aqua regia, and evaporated al most to dryness, so as to expel the nitric acid, sulphuric dioxide being then passed through it until all the gold is precipitated. Upon this it is oxidated to bring all the platinum into a platinic state and precipitated with pure am monium chloride. The precipitate is now re duced in the usual way to metallic platinum sponge.