Chemistry: Platinum is a relatively rare, chemically inert, metallic element. Its symbol is Pt, atomic number 78, and atomic weight 195.09.
Platinum is one of the heaviest substances known. One cubic foot of Platinum weighs 21 times as much as a cubic foot of water. It is a grayish-white metal with a melting point of 1772 degrees C and a relatively high boiling point of 3827 degrees C. Platinum has a high fusing point, is ductile and malleable, expands slightly upon heating, and has high electrical resistance. It is seldom used in its pure stage because it is too soft. Platinum is the third most ductile metal and can be drawn into a thread one twenty thousandth part of an inch in thickness.
It is extremely resistant to attack by air, water, single acids, and ordinary reagents, but it does dissolve in hot aqua regia, a mixture of nitric and hydrochloric acids. Platinum has the unusual property of being able to absorb large amounts of hydrogen at ordinary temperatures and resist it at high temperatures. The first mention of Platinum occurs in the writings of an Italian physician and poet named Julius Caesar Salinger in 1557. A hieroglyphic character made from a grain of Platinum dated back to the 7th century. Credit for the discovery of Platinum has been given to Don Antonio de Ulloa, a young lieutenant in the Spanish Navy.
The metal was referred to as platina de Pinto,” meaning the silver-like metal from the Pinto River. The first thorough study of platinum was conducted in 1750 by the English physician William Brownrigg. Brownrigg noted that platinum was heavier and even more chemically inert than gold. Platinum forms useful alloys with many other metals, including iridium, palladium, rhodium, ruthenium, osmium, gold, nickel, cobalt, and tungsten.
At high temperatures, platinum reacts with chlorine, fluorine, phosphorus, arsenic, and sulfur. Among the transition metals, platinum has the greatest tendency to bond directly with carbon. Platinum is extensively used in modern industrial society due to its chemical inertness, high melting point, and extraordinary catalytic properties. It is valuable for laboratory apparatus such as tongs, combustion boats, crucibles, and evaporating dishes. Additionally, it is used for thermometers in furnaces, electrodes in making quantitative chemical analyses, and corrosion and heat-resistant instruments. Platinum is also extensively used in the jewelry industry for setting diamonds and other precious stones.
Rocket and jet engine parts often contain platinum alloys because they must withstand high temperatures for long periods of time. At petroleum refineries, finely divided platinum is used as a catalyst in upgrading the octane of gasoline. In automobiles, converters containing platinum-palladium alloys reduce air pollution from exhaust gases. High-quality optical glass for television picture tubes and eyeglasses is melted in pots lined with nonreactive platinum alloys. A form of platinum, cisplatin, stops cancer cell division and disrupts its growth pattern.
