Platinum – Definition, Occurrence, Properties, Applications

Platinum and its alloys are essential in the chemical laboratory for electrodes, crucibles, and dishes in which materials can be heated to high temperatures. Platinum is one of the most prevalent platinum metals. Because platinum resists both the high temperatures and chemical attack of electric arcs, it is utilised for electrical contacts and sparking points. The majority of its applications are in jewellery and dental alloys; platinum-iridium is utilised in surgical pins.

It was not known until fifty years after platinum was discovered in South America and early analyses of its properties by a number of French, German, Swedish, and English scientists that the native platinum they were researching also contained other elements.

What is Platinum?

Platinum occurs in some nickel and copper ores, as well as some native deposits, primarily in South Africa, which accounts for 80% of global production. Because of its scarcity in the Earth’s crust, only a few hundred tonnes are produced each year, and given its important applications, it is a highly valuable and a major precious metal commodity.

Platinum has the chemical symbol Pt and the atomic number 78. It is a silverish-white transition metal that is dense, malleable, ductile, and highly unreactive.

Platinum belongs to the platinum group and group 10 of the periodic table of elements. It has six isotopes that occur naturally. It is one of the more rare elements found in the Earth’s crust.

Occurrence of Platinum

Platinum is an extremely rare metal that occurs in the Earth’s crust at a concentration of only 0.005 ppm. It is sometimes confused with silver. Platinum is frequently found chemically uncombined as native platinum and as an alloy with the other platinum-group metals, primarily iron. Native platinum is typically found in secondary deposits in alluvial deposits. Colombia is an important source of platinum-group metals. Another large alluvial deposit exists in Russia’s Ural Mountains and is still mined.

Platinum-group metals are found in nickel and copper deposits as sulphides, tellurides, and end alloys with nickel or copper. In Canada, platinum arsenide is a major source of platinum associated with nickel ores.

Platinum is found in greater abundance on the Moon and in meteorites. Platinum, which can be mined economically, is found in slightly higher abundances at sites of bolide impact on Earth that are associated with resulting post-impact volcanism.

Properties of Platinum

• Platinum is a silver-coloured metal that is soft and lustrous.
• It has a high density, is malleable, and is ductile.
• It is also resistant to corrosion and has a high boiling point.
• Platinum is one of the most chemically stable elements found in nature. Because of its high stability, it is frequently referred to as a Noble metal.
• It is resistant to nitric and hydrochloric acids, but it can be dissolved at high temperatures by aqua regia.
• Platinum is a noble metal, which means it is chemically stable.
• It does not tarnish in the air because it does not react with the oxygen present.
• It is also impervious to acid attacks.
• Halogens, cyanides, sulphur, and alkalis corrode it.
• Platinum absorbs large amounts of hydrogen gas at high temperatures in the same way that a sponge absorbs water, which is an unusual property of platinum.
• Platinum has a strong proclivity to form complex ions. Pt(I), which has a planar structure and is diamagnetic, is the most common.

What are some Environmental Effects of Platinum?

Platinum is emitted into the atmosphere by the exhausts of vehicles that run on leaded gasoline. As a result, platinum levels in the air may be higher in certain locations, such as garages, tunnels, and trucking company terrains.

Platinum accumulates in the roots of plants after absorption, but it is unclear whether it can harm animals or humans.

In soils, microorganisms may be able to convert platinum substances to more dangerous substances, but we also know very little about this.

Uses and Application of Platinum

1. Its wear and tarnish-resistance properties make it ideal for making fine jewellery.
2. Platinum and its alloys are used in surgical instruments, laboratory equipment, electrical resistance wires, and electrical contact points.
3. It is used as a catalyst (30%) in the catalytic converter, which is an optional component of the gasoline-powered automobile exhaust system.
4. The chemical, electrical, glass, and aircraft industries each use about 10 tonnes of platinum per year, accounting for the majority of its use (50%).
5. Platinum is used in the glass industry for optical fibres and liquid crystal display glass, particularly for laptops.
6. It is also found in laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dental equipment, and jewellery.
7. As it is a heavy metal, exposure to its salts causes health problems; however, due to its corrosion resistance, metallic platinum has not been linked to adverse health effects.

Compounds of Platinum

• Halides: Hexachloroplatinic acid is the most important platinum compound because it is the precursor for many other platinum compounds. It is used in photography, zinc etchings, indelible ink, plating, mirrors, porcelain colouring, and as a catalyst.
• Oxides: PtO₂, or platinum(IV) oxide, is a black powder that is soluble in potassium hydroxide solutions and concentrated acids.

Sample Questions

Question 1: How is platinum extracted?

Answer:

After crushing the ore, the Froth-Flotation process is completed. During Flotation, air is passed through an ore-water mixture known as Slurry. The platinum particle is chemically attached to the oxygen that rises to the surface in a froth and is then skimmed off for further refining. It is then dried and heated to 1500° C in an electric furnace before being blown through with air to remove iron and sulphur impurities. After that, aqua regia is used to dissolve platinum metal from the mineral concentrate by producing chlorine, which binds to platinum to form chloroplatinic acid.

Finally, ammonium chloride is used to convert chloroplatinic acid to ammonium hexachloroplatinate, which is then burned to produce pure platinum metal.

Question 2: What is a platinum hunk?

Answer:

Platinum and platinum alloys are used to create platinum hunk, which serves as an international standard for weighing a kilogram.

Question 3: Can we dissolve Platinum in Aqua Regia?

Answer:

Platinum is not attacked by acids due to its chemical inertness. However, platinum is easily soluble in Aqua Regia, a 1:3 mixture of concentrated nitric and hydrochloric acid. As both acids are concentrated, the mixture is extremely volatile. The main cause of noble metal dissolution is its volatile nature. Noble metals such as gold, palladium, and platinum are soluble in Aqua Regia but not in either acid alone. Aqua regia dissolves metals by oxidising them first.

Question 4: Which is the most unreactive metal known?

Answer:

Platinum is the most unreactive metal.

Question 5: Define aqua-regia.

Answer:

Aqua regia is a 3:1 mixture of concentrated hydrochloric acid and nitric acid. It is extremely corrosive and can dissolve precious metals such as gold and platinum.