Discovered in South America by Ulba in 1735 and by Wood in 1741. The metal was used by pre- Colombian Indians. Platinum occurs native, accompanied by small quantifies of iridium, osmium, palladium, ruthen- ium, and rhodium, all belonging to the same group of metals. These are found in the alluvial deposits of the Ural moun- tains, of Colombia, and of certain western American states. The large production of nickel offsets the fact that there is only one part of the platinum metals in two million parts of ore.
Platinum is a beautiful silvery-white metal, when pure, and is malleable and ductile.
It has a coefficient of expansion almost equal to that of soda4ime- silica glass, and is therefore used to make sealed electrodes in glass systems. The metal does not oxidize in air at any temperature, but is corroded by halogens, cyanides, sulfur, and caustic alkalis. The metal is extensively used in jewelry, in wire and vessels for laboratory use, and in many valuable instruments, in- cluding thermocouple elements. It is also used for electrical contacts, corrosion-resistant apparatus, and in dentistry. The metal is used for coating missile nose cones, jet engine fuel nozzles, etc., which must perform reliably for long periods of time at high temperatures.