During some archeological expeditions was possible to find evidence that first human been found along with gold nuggets of platinum, which were known as white gold in Egypt and Spain and frog’s gold in Borneo. Probably, in old times, mirrors, jewelry, ornaments and household utensils were fabricated with platinum and alloys of platinum with gold. Some researches consider that platinum had been forgotten by the beginning of our era and was not recognized until after Spanish conquest of South America. In the European medieval writings, platinum was referred to as a bright unmeltable metal. In 1537, platinum was officially discovered and the first scientific description of platinum was published in the Proceedings of the Royal Society, England.
It has been established that in the late 18th century, platinum came to the increasing attention of chemists. Coincident with the detailed study of the metal, the developments of methods for making malleable platinum was begun. In this way, pure platinum was first obtained in 1803 by Wollaston. This scientist developed the first method of producing malleable platinum on industrial scale. The research work performed on platinum made possible to discover other elements, palladium and rhodium. Iridium and osmium were obtained from black sediment that platinum leaves on dissolution in aqua regia. In Russia, platinum was found in 1819 and the first alluvial deposit of commercial importance was found in the Urals in 1824.
Platinum occurs in small, flat particles or pebbles in alluvial sands, and the native metal usually contains other metals of the platinum group metals. The largest nugget ever was found in South America. The main sources of platinum are in Russia and smaller amounts are in Alaska, Canada and South Africa. Some platinum is obtained as a by-product of the treatment of nickel-copper ores in Canada and South Africa. Some platinum minerals are sperrrylite and cupperite. The first one is a platinum arsenide and the other is a platinum sulphide. Commercial platinum is 99.8 to 99.9% pure with some iridium.
Platinum has a high resistance to corrosion even in sulphur environments. Platinum coatings are employed on springs and other functioning parts of instruments and electronic devices where precise operation is essential. Electroplating may be done with an electrolyte bath of platinum dichloride or platinum tetrachloride. Some coating can be obtained by vapor deposition of platinum compounds. Special coatings as fine as 0.00005 mm are obtained by painting the surface with a solution of platinum powder. Platinum is more ductile than silver, gold or copper. The melting point is 1769 oC and the specific gravity is 21.5. Electrical conductivity is about 16% of that of copper. It is resistant to acids and alkalis, but dissolves in aqua regia. This metal is employed in jewelry and due to its heat resistance and chemical resistance it is valued for electrical contacts and resistance wire and laboratory dishes. Generally too soft for use alone, it is almost always alloyed with harder metals of the same group (rhodium, iridium and palladium).