Rhenium is a silvery-white metal that has the highest boiling point and third highest melting point of any chemical element. It is represented by the atomic number 75 and the chemical symbol Re. It was discovered in 1925 and was the last stable element ever to be discovered. One of the reasons for this is that it is one of the rarest elements in the crust of the earth. It is not thought to occur in its free form in nature, but can be found in certain minerals. The most important of these minerals is molybdenite, which usually contain 0.001% to 0.2% rhenium (although samples have been found up to contain up to 1.88%). China is the largest producer of this metal, but it remains rare and expensive. Despite this fact, there are many important applications of rhenium.
Uses of rhenium
- Rhenium is an important part of many superalloys. These alloys may contain about 3-6% of the metal. They are most commonly used in the aerospace industry as turbine blades for jet engines. Rhenium also improves the properties of tungsten and these two metals are commonly alloyed together. This alloy is most commonly used as the target in medical X-ray tubes because it is stable, strong and crack resistant.
- Rhenium is also an important catalyst (a substance that causes and/or speeds up a chemical reaction). It is a popular choice because the catalyst reaction is not affected by nitrogen, sulfur and phosphorus. It is commonly used in the petroleum industry to produce high-octane unleaded gasoline.
- Rhenium is also used in self-cleaning electrical contacts, mass spectrometers, ion gauges, and in photography flashes.
- Two radioactive isotopes of rhenium, 188Re and 186Re, are used to treat liver cancer.