What is Platinum? | Element data, Properties and Uses

What is Platinum?

Platinum is a silverish-white metal that mainly occurs in its native form, the symbol is Pt and the atomic number is 78 and the atomic weight is 195.09. Its located in the d-block elements 10th group and 6th period of the periodic table. Its electronic configuration is  [Xe] 4f14 5d9 6s1. It has six naturally occurring isotopes. The most abundant isotope is 195Pt. Its oxidation states ranges from +1 to +4 of which Pt (+2) and Pt (+4) are the common oxidation states. 

Occurrence

Platinum usually occurs in its native form along with copper, gold, iron, and other metals in sands and gravels. Platinum deposits are mainly found in Russia, Columbia, and South Africa. In a combined state it is found in sperrylite, cooperite,  and braggite.

Extraction

Platinum is extracted from Sudbury nickel ore. The ore is concentrated to remove iron, nickel, and copper sulfides. It is then digested with aqua regia under pressure.

The solution obtained contains PdCl2 and PtCl4. This solution is treated with NH4Cl.  The PtCl4 is converted to (NH4)2[PtCl6] complex which is a yellow precipitate and the PdCl2 remains unreacted in the solution. The yellow precipitate is then heated to give the spongy platinum metal.

Properties

Platinum is a white silvery metal. Its melting point is 1768 °C and its boiling point is 3825 °C. It joins with glass, as its coefficient of expansion is the same as that of glass. At red heat temperature, it allows hydrogen to pass through. Platinum is not attacked by sulphuric acid, but it dissolves in aqua regia. The alloy of lead and platinum dissolves in nitric acid forming platinum nitrate. Platinum density is 21.45 g/cm3.

Types of Platinum

1. Spongy platinum:

When ammonium Platino chloride, (NH4)2PtCl6 is gently heated, a gray porous form is obtained known as spongy platinum. It has good surface activity. so it is used for the adsorption of gasses.

2. Platinum black:

The alloy of platinum with copper or zinc is treated with nitric acid, and the nascent hydrogen reduces the platinum salt and falls back as a black powder. It is obtained by reducing platinic chloride with formaldehyde or by reducing chloroplatinate with sodium formate.Platinum black absorbs more hydrogen than spongy platinum (160 volumes). The absorption is maximum at 0 ℃. So it is used for commercial reduction processes.

3. Platinized asbestos:

Asbestos is soaked with platinic chloride and little HCl and some ammonium chloride, heated or reduced with sodium formate, platinum precipitates in the fibers of the asbestos. It finds extensive use as a catalyst.

4. Colloidal platinum:

It is prepared by Bredig's method, by passing electricity between two platinum terminals dipped in water. It can also be prepared by reducing platinic chloride with hydrazine hydrate in the presence of protective colloids. It's also a catalyst, it decomposes hydrogen peroxide catalytically.

Uses

1. Scientific instruments and Laboratory apparatus: Due to their high melting point, and corrosion resistance. It is used to manufacture crucibles, dishes, basins, etc. Pt is used for contacts in electrical apparatus and for making electrodes. 

2. Catalyst: It is used as a catalyst in many organic and inorganic reactions. Some important applications as a catalyst are listed below.

3. Production of sulphuric acid: Platinised asbestos is used in the Contact process.

4. Production of nitric acid:  Platinum gauge is used in the Ostwald's process.

5. Preparation of formaldehyde: Platinum black is used.

6. Preparation of HBr and HI: Red hot finely divided platinum is used.

7. Hydrogenation and dehydrogenation reactions: Finely divided platinum has been used, as it’s having the property of absorbing several times of hydrogen gas.

8. Platinum is used in petroleum industries, synthetic fiber, and glass industries.

9. Adam's catalyst: PtO2 is used in the hydrogenation of vegetable oils.

10. Jewelry: Platinum is used in jewelry as a setting for diamonds. For this, it's alloyed with metals like Iridium, ruthenium, or copper. Iridium-platinum alloy is used in pen points, standard weights, coins, etc.

11. Dentistry:  It is used in artificial teeth, pins dental fillings, and support for dentures.

12. Platinum salts are used in printing and toning in photography.

13. Pt wire is used in qualitative analysis.

14. Medical instruments like X-ray tubes, radium applications, and lypodermic needles require platinum.