Rhenium

Category: transition metal Atomic number: 75 Colour: silvery Melting point: 3,186°C (5,767°F) Boiling point: 5,596°C (10,105°F) First identified: 1925

There were a couple of false starts in the discovery of rhenium. In 1908, the Japanese chemist Masataka Ogawa isolated the element, which he called nipponium, but he wrongly announced that he had found element 43, so his findings were discredited. Rhenium was once again isolated in Germany in 1925 by Walter Noddack, Ida Tacke (who later married Noddack) and Otto Berg – they needed 660 kilograms of the ore molybdenite to produce a single gram of the metal (it is still produced as a by-product of the purification of copper and molybdenum) but also found it in gadolinite. They wrongly announced that they had found both elements 43 and 75, which harmed their reputation, but it was finally established that rhenium (named after the Rhine river) was indeed number 75. It was also the last naturally occurring metal to be discovered.

Rhenium is rare and usually found in nature with other metals, although some rhenium disulphide (a compound with sulphur) has been found at the mouth of a volcano in Eastern Russia. Rhenium dibromide is a super-hard material that, unlike diamonds, can be manufactured outside an extreme high-pressure environment.

Nuclear Error

The Noddacks’ mistake in announcing they had found element 43 had one particularly unfortunate consequence. In 1934, Ida Noddack suggested that nuclear fission might be possible, but with her reputation having been damaged, the suggestion was ignored. The discovery of fission would be credited to Otto Hahn, Lise Meitner and Fritz Strassmann, who in 1938 became the first to recognize that the uranium atom, when bombarded by neutrons, actually split.

However, rhenium is mostly used, alloyed with nickel and iron, in the turbines of fighter aircraft. It is also a useful catalyst, which can be deployed in the manufacture of high-octane and lead-free petrol. And it can be used in alloys with tungsten and molybdenum, which are extremely hard and heat-resistant.