Platinum is a precious and strong metal and has been known since ancient times. It was formally discovered in 1753 in South America.
History and Discovery
Platinum is an ancient metal, as in around 1200 BC, it was identified as a contamination in gold in ancient Egypt. The traces of platinum have been found in pre-Columbia American civilizations, where it was used in making artifacts of white gold. Later, Antonio de Ulloa and Don Jorge Juan (1753) found raw platinum from mines and studied its chemical and physical properties in 1748 and identified it as a distinct metal [1]. In 1752, Henrik Scheffer published a comprehensive description of the novel metal as termed it as “white gold”. The name platinum has been derived from the word platino, which is the Spanish word for little silver [2].
Platinum
| Periodic Table Classification | Group 10 Period 6 |
|---|---|
| State at 20C | Solid |
| Color | Silvery white |
| Electron Configuration | [Xe] 4f14 5d9 6s1 |
| Electron Number | 78 |
| Proton Number | 78 |
| Electron Shell | 2, 8, 18, 32, 17, 1 |
| Density | 21.45 g.cm-3 at 20°C |
| Atomic number | 78 |
| Atomic Mass | 195.08 g.mol -1 |
| Electronegativity according to Pauling | 2.28 |
Occurrence
Platinum is a rare transition metal. It is present in a concentration of as low as around 0.005 ppm (5micrograms per kg) in the Earth’s crust. Platinum is mostly present in its native form and as alloy with iron. It is primarily prevalent in the alluvial deposit layer along with sand and clay particles. Various ores, including copper and nickel deposits contain platinum in combination with sulfide, arsenide and antimonides. The most common ore of platinum is sperrylite (PtAs2). Cooperite ((Pt,Pd,Ni)S is the sulfide ore of platinum and is present in South Africa, although this ore is quite rare. The largest platinum deposits are present in South Africa, India, Colombia and Russia [3].
Physical Characteristics
Platinum is a silvery white, beautiful metal. It is ductile, lustrous and malleable and is considered the most ductile metal [4]. Platinum is highly stable at high temperature and has a high boiling point (3800 °C). It is very resistant to corrosion. Platinum is a fair conductor of electricity. Platinum is not tarnished in the presence of air or heat. It does not react with acids but is readily dissolved in aqua regia (mixture of concentrated hydrochloric acid and nitric acid). The atomic number of platinum is 78 and its atomic mass is 195.09.
Chemical Characteristics
Platinum is a chemically stable element as it is one of the least reactive metals (Nobel metal). platinum have two oxidation states, +2 and +4. Platinum readily reacts with carbon. Certain non-metals, including phosphorus, silicon and sulfur also combine with platinum. Platinum is readily attacked by peroxides and fluorine at high temperatures. Platinum (IV) also forms oxide, PtO2 (also called Adam’s catalyst).
Significance and Uses
- Platinum is widely used as a catalyst in exhaust system of internal combustion engine where it is part of the catalytic converter.
- Platinum is used in making ornaments, artifacts and jewellery.
- Platinum is used in making dental alloys and implants.
- Various surgical tools, and laboratory utensils are made of platinum.
- Platinum is used in making electrical contact points and resistance wires.
- Platinum is used in aircraft and sport car industries.
- Platinum is used in making liquid glass display in laptops
- Platinum is used to make optical fibers.
Health Hazards
Platinum is non-toxic, but certain salts of platinum are considerably dangerous and carcinogenic. Platinum toxicity is primarily an occupational hazard, as it is emitted from cars and vehicles with leaded gasoline. And personals working at garages and terrains of automobile companies are considered be at risk of platinum toxicity. The exposed individual can experience irritation of throat, eyes and nose and continuous exposure can develop skin allergies and respiratory trouble. There are certain health care standards that propose that about 1 mg/m3 over an 8-hour workday is considered as a harmless exposure limit (REL) for individuals exposed to platinum [5].
Isotopes of Platinum
Platinum has 35 isotopes. There are six isotopes in naturally occurring platinum: platinum-190, platinum-192, platinum-194, platinum-195, platinum-196 and platinum-198. The most abundant and the only stable isotope is platinum-195.
REFERENCES
[1]. Weeks, M. E. (1968). Discovery of the Elements (7th ed.). Journal of Chemical Education. pp. 385–407. ISBN 978-0-8486-8579-9. OCLC 23991202.
[2]. Harper, Douglas. “platinum”. Online Etymology Dictionary.
[3]. Loferski, P. J. (July 2012). “Platinum–Group Metals” (PDF). USGS Mineral Resources Program. Archived (PDF) from the original on 7 July 2012. Retrieved 17 July 2012
[4]. Lagowski, J. J., ed. (2004). Chemistry Foundations and Applications. 3. Thomson Gale. pp. 267–268. ISBN 978-0-02-865724-0.
[5]. “CDC – NIOSH Pocket Guide to Chemical Hazards – Platinum”. www.cdc.gov. Archived from the original on 21 November 2015. Retrieved 21 November 2015.