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Platinum (Pt) was discovered by Ulloa in 1735 and Wood in 1741. Platinum occurs as such naturally, together with negligible amounts of palladium, iridium, rhodium, osmium, and ruthenium. All these elements belong to the same group of metals. It does not have any commercial ore and occurs in two rare minerals—cooperite (PtS) and sperrylite (PtAs2).
Pure platinum is a splendid silvery-white metal that is heavier than gold. It is more ductile than gold, copper, or silver, and is malleable.
Although platinum does not oxidize in air at any temperature, it is corroded by cyanides, halogens, caustic alkalis, and sulfur. It does not dissolve in nitric and hydrochloric acids. However, when they are combined to form aqua regia, platinum gets dissolved and forms chloroplatinic acid (H2PtCl6). In the presence of platinum, oxygen and hydrogen tend to explode.
The face-centered-cubic lattice structure of platinum makes it highly ductile and malleable. Since it is usually too soft to be used alone, it is combined with harder metals of the same group to form alloys, such as iridium, osmium, and rhodium.
When fine platinum wire is placed in methyl alcohol vapor, it glows red-hot.
Platinum is extensively used in:
- Electrical contacts
- Corrosion-resistant devices
- Platinum wire is used in high-temperature electric furnaces
- Instrumentation devices
- Resistance wire
- As foil (99.99% pure) for maximum softness in dentistry
- Standard weights
- Laboratory vessels and dishes
- As an anode for cathodic protection systems for pipelines, large ships and ocean-going vessels, steel piers, and the like
- Can be produced in various forms such as flake, powder, gauze, coating, and foil
Platinum is used as a catalyst in gauze form for the contact process, which produces sulfuric acid, in cracking petroleum products to a lesser extent. An example of this is the conversion of alcohol vapor into formaldehyde. It has been successfully used in commercial products such as hand warmers and cigarette lighters, in antipollution devices for automobiles, and as a catalyst in fuel cells.
The platinum metal is used in the form of a coating on missile nose cones, jet engine fuel nozzles, and similar applications that require performance reliability for long periods at high temperatures and/or resistance to atmospheric corrosion, even in sulfur environments.
Occasionally, platinum is alloyed with other elements like:
- Tungsten—Used in radar-tube grids, aircraft-engine spark plug electrodes, heating elements, strain gauges, and switches
- Cobalt—For the production of a very strong magnet that offers a B-H (max) almost twice that of Alnico V