Platinum

What is Platinum?

Platinum is the most valued precious metal; its value exceeds even that of Gold. It has a beautiful silver-white colour, and, unlike Silver, does not tarnish. It is unaffected by common household chemicals and will not get damaged or discoloured by chlorine, bleach, or detergents. It is tougher than all precious jewellery metals, though due to its flexible tenacity it still must be alloyed with other metals to prevent it from bending. Natural Platinum usually contains small amounts of the rare element iridium. In jewellery, iridium is alloyed with the Platinum to increase its toughness. Platinum jewellery is usually 90 to 95 percent pure.
Platinum is one of the least reactive metals. It has remarkable resistance to corrosion, even at high temperatures, and is therefore considered a noble metal. Consequently, platinum is often found chemically uncombined as native platinum. Because it occurs naturally in the alluvial sands of various rivers, it was first used by pre-Columbian South American natives to produce artefacts. It was referenced in European writings as early as 16th century, but it was not until Antonio de Ulloa published a report on a new metal of Colombian origin in 1748 that it began to be investigated by scientists.
Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewellery. Being a heavy metal, it leads to health issues upon exposure to its salts; but due to its corrosion resistance, metallic platinum has not been linked to adverse health effects. Compounds containing platinum, such as cisplatin, oxaliplatin and carboplatin, are applied in chemotherapy against certain types of cancer.

About Platinum

  • Atomic number (number of protons in the nucleus): 78
  • Atomic symbol (on the periodic table of elements): Pt
  • Atomic weight (average mass of the atom): 195.1
  • Density: 12.4 ounces per cubic inch (21.45 grams per cubic cm)
  • Phase at room temperature: solid
  • Melting point: 3,215.1 degrees Fahrenheit (1,768.4 degrees Celsius)
  • Boiling point: 6,917 F (3,825 C)
  • Number of natural isotopes (atoms of the same element with a different number of neutrons): 6. There are also 37 artificial isotopes created in a lab.
  • Most common isotopes: Pt-195 (33.83 percent of natural abundance), Pt-194 (32.97 percent of natural abundance), Pt-196 (25.24 percent of natural abundance), Pt-198 (7.16 percent of natural abundance), Pt-192 (0.78 percent of natural abundance), Pt-190 (0.01 percent of natural abundance)

Platinum History (The "unmeltable" metal)

In ancient times, people in Egypt and the Americas used platinum for jewellery and decorative pieces, often times mixed with gold. The first recorded reference to platinum was in 1557 when Julius Scaliger, an Italian physician, described a metal found in Central America that wouldn't melt and called it "platina," meaning "little silver." 
In 1741, British scientist Charles Wood published a study introducing platinum as a new metal and described some of its attributes and possible commercial applications, according to Peter van der Krogt a Dutch historian. Then, in 1748, Spanish scientist and naval officer Antonio de Ulloa published a description of a metal that was unworkable and unmeltable. (He originally wrote it in 1735, but his papers were confiscated by the British navy.) 
Back in the 18th century, platinum was the eighth known metal and was known as "white gold," according to van der Krogt. (Previously known metals included iron, copper, silver, tin, gold, mercury and lead.)
In the early 1800s, friends and colleagues William Hyde Wollaston and Smithson Tennant, both British chemists, produced and sold purified platinum that they isolated using a technique developed by Wollaston, according to van der Krogt This technique involves dissolving platinum ore in a mixture of nitric and hydrochloric acids (known as aqua regia). After the platinum was separated from the rest of the solution, palladium, rhodium, osmium, iridium, and later ruthenium were all discovered in the waste.
Today, platinum is still extracted using a technique similar to that developed by Wollaston. Samples containing platinum are dissolved in aqua regia, are separated from the rest of the solution and byproducts, and are melted at very high temperatures to produce the metal.

Occurrence of Platinum

Platinum is an extremely rare metal, occurring at a concentration of only 0.005 ppm in Earth's crust. It is sometimes mistaken for silver (Ag). Platinum is often found chemically uncombined as native platinum and as alloy with the other platinum-group metals and iron mostly. Most often the native platinum is found in secondary deposits in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum-group metals. Another large alluvial deposit is in the Ural Mountains, Russia, and it is still mined.
In nickel and copper deposits, platinum-group metals occur as sulfides (e.g. (Pt,Pd)S), tellurides (e.g. PtBiTe), antimonides (PdSb), and arsenides (e.g. PtAs2), and as end alloys with nickel or copper. Platinum arsenide, sperrylite (PtAs2), is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. At Platinum, Alaska, about 17,000 kg (550,000 ozt) had been mined between 1927 and 1975. The mine ceased operations in 1990. The rare sulfide mineral cooperite, (Pt,Pd,Ni)S, contains platinum along with palladium and nickel. Cooperite occurs in the Merensky Reef within the Bushveld complex, Gauteng, South Africa.
In 1865, chromites were identified in the Bushveld region of South Africa, followed by the discovery of platinum in 1906. The largest known primary reserves are in the Bushveld complex in South Africa. The large copper–nickel deposits near Norilsk in Russia, and the Sudbury Basin, Canada, are the two other large deposits. In the Sudbury Basin, the huge quantities of nickel ore processed make up for the fact platinum is present as only 0.5 ppm in the ore. Smaller reserves can be found in the United States, for example in the Absaroka Range in Montana. In 2010, South Africa was the top producer of platinum, with an almost 77% share, followed by Russia at 13%; world production in 2010 was 192,000 kg (423,000 lb).
Platinum deposits are present in the state of Tamil Nadu, India.
Platinum exists in higher abundances on the Moon and in meteorites. Correspondingly, platinum is found in slightly higher abundances at sites of bolide impact on Earth that are associated with resulting post-impact volcanism, and can be mined economically; the Sudbury Basin is one such example.

Properties of Platinum

Chemical FormulaPt
ColourMetallic, White
Hardness4 - 4.5
Crystal SystemIsometric
SG14 - 19
TransparencyOpaque
Double RefractionNone
LusterMetallic
CleavageNone
Mineral ClassPlatinum

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