Rhenium Re

Discovery

Mendeleev's table left two gaps below manganese, at elements 43 and 75. In 1925 Walter Noddack, Ida Tacke (later Ida Noddack) and Otto Berg in Germany reported the X-ray lines of element 75 in platinum ores and columbite. They also claimed element 43, naming it "masurium", but that claim was not accepted.

In 1928 the Noddacks processed 660 kg of molybdenite to extract about one gram of rhenium. Separately, in 1908 the Japanese chemist Masataka Ogawa had announced element 43 as "nipponium"; later re-analysis suggested that what he had actually found was probably rhenium.

Ida Noddack is also remembered for suggesting in 1934 that uranium bombarded with neutrons might break into large fragments. The idea was largely ignored at the time but was vindicated by the discovery of nuclear fission a few years later.

Origin of the name

The name comes from Rhenus, the Latin name of the river Rhine, honouring the discoverers' homeland.

Main uses

• Superalloys: a few percent of rhenium in single-crystal nickel superalloys greatly reduces creep at high temperatures, so it is used in turbine blades for jet engines and power-generation gas turbines. This accounts for most rhenium demand.
• Reforming catalysts: platinum-rhenium catalysts convert naphtha into high-octane petrol components.
• High-temperature sensing and electrical parts: tungsten-rhenium thermocouples measure temperatures above 2,000 °C, and rhenium is used in electrical contacts and filaments.

Isotopes

Natural rhenium consists of stable rhenium-185 (about 37%) and radioactive rhenium-187 (about 63%), so most natural rhenium is radioactive. Rhenium-187 beta-decays to osmium-187 with a half-life of about 41 billion years, and the rhenium-osmium method is used to date ore deposits and meteorites. Rhenium-186 and rhenium-188 are studied for radiotherapy.

In everyday life

Rhenium is recovered mostly as a by-product of refining copper and molybdenum ores, with Chile among the leading producers. Because it is scarce and costly, it goes almost entirely into high-value uses such as aircraft engines. A rhenium sulfide mineral was found at a volcanic vent in Russia's Kuril Islands, a rare example of rhenium forming its own mineral. The toxicity of rhenium has not been studied extensively but is generally regarded as low.