Rhenium is the chemical element with atomic number 75, symbol Re.
The simple rhenium body is a silvery metal which resists corrosion well and has
an exceptional tolerance to heat. It has the particularity of not being attacked
by hydrochloric acid or sulfuric acid, but it dissolves in nitric acid.
Rhenium has few applications, due to its rarity and high production costs (its
estimated price was $ 3,200 / kg in 2013, in the form of 99.99% pure pellets 6),
but its use in aeronautics is strategic7. It is usually extracted from
molybdenum dust, in industrial ovens, of which it is a powdery by-product of
gray color, but rhenium is also found in trace amounts in certain minerals.
Rhenium is used to improve the thermal resistance of the filament in electric
ovens, in the production of thermocouples and as a catalyst in the chemical
industry.
Pure rhenium is a hard, corrosion-resistant, silvery-white metal. It has the
third highest melting point (3,180 กใ C) of all single bodies after tungsten and
carbon. It also has the highest boiling point of all the elements. Rhenium
powder is slowly oxidized in air to rhenium heptoxide (Re2O7) above 150 กใ C. The
element has been characterized in the oxidation states -1 to +7, the states +3,
+4, +5 and +7 being the most common9.
Isotopes
Main article: Isotopes of rhenium.
Rhenium has 35 known isotopes, with a mass number varying between 160 and 194,
as well as 21 nuclear isomers. Among these isotopes, only one is stable, 185Re,
making rhenium a monoisotopic element. However, like vanadium, rubidium,
lutetium, lanthanum, europium and indium, it coexists with a long-lived natural
radioisotope, 187Re (half-life of 41.2 billion d years, three times the age of
the universe) which makes rhenium not a mononucleidic element. As in the cases
of indium and tellurium, this radioisotope is even the most abundant isotope
(62.6 against 37.4%). Rhenium is assigned a standard atomic mass of 186.207 (1)
u.
Production
World production is around 50 tonnes per year10. Rhenium is extracted from
molybdenite or copper sulphide in the form of heptoxide (Re2O7) which is then
converted into ammonium perrhenate (NH4ReO4) before being reduced to metallic
rhenium in the presence of hydrogen9.
The three main producing countries are11:
Chile (42% of world production);
the United States (17% of world production);
Kazakhstan (17% of world production).
magnesium bismuth manganese chromium cobalt titanium
Tungsten vanadium niobium indium molybdenum antimony
rhenium germanium zirconium cadmium hafnium
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