Facts about Rhenium
Commercial rhenium is extracted from molybdenum roaster-flue dusts obtained from copper sulfide ores.
Rhenium is combined with platinum to form catalysts that are used primarily for making lead-free, high-octane gasoline.
The process was so complicated and the cost so high that production was discontinued until early 1950, when tungsten-rhenium and molybdenum-rhenium alloys were prepared.
Little is known about the toxicity of rhenium, but as a precautionary measure, it should be handled with care.
Recycling of used platinum-rhenium catalyst and special alloys allow the recovery of another ten tons/year.
The melting point of rhenium is among the highest of all elements, exceeded only by the melting points of tungsten and carbon.
The usual commercial form of rhenium is a powder, but it can be consolidated by pressing and resistance-sintering in a vacuum or hydrogen atmosphere.
Rhenium (chemical symbol Re, atomic number 75) is a silvery-white, lustrous, rare metal.
In 1994, Nature published a letter describing a rhenium sulfide mineral found condensing from a fumarole on Russia's Kudriavy volcano.
Rhenium is also one of the densest, exceeded only by the densities of platinum, iridium, and osmium.
Naturally occurring rhenium is a mix of 185Re, which is stable, and 187Re, which is radioactive but has a very long half-life.
Rhenium is widely spread in the Earth's crust, at approximately 0.001 parts per million (ppm), but it is not found free in nature.
Rhenium-molybdenum alloys are superconductive at ten Kelvin (K), and tungsten-rhenium alloys are superconductive around four to eight K, depending on the alloy.
The oxidation states of rhenium include -3,-1,+1,+2,+3,+4,+5,+6 and +7.