rhenium

Rhenium is a chemical element with the symbol Re and the atomic number 75. It is a rare, dense, silvery-white transition metal notable for its exceptionally high melting and boiling points, with a melting point of about 3,179 C and a boiling point around 5,596 C. It is highly resistant to corrosion and retains strength at high temperatures, making it valuable for demanding engineering applications.

Occurrence and production: Rhenium is extremely rare in the Earth's crust and is almost always obtained as a byproduct of molybdenum and copper mining. It is commonly recovered from molybdenite and related minerals during refining. Commercially, rhenium is produced from ammonium perrhenate (NH4ReO4), which is subsequently reduced to metallic rhenium.

Isotopes and dating: The element has two naturally occurring isotopes, 185Re and 187Re; 187Re is radioactive and decays slowly to 187Os with a half-life of about 4.1 × 10^10 years, while 185Re is stable. The Re-Os dating method leverages this decay.

Applications: Rhenium strengthens high-temperature nickel- and cobalt-based superalloys used in jet engines and gas turbines. It also serves as a catalyst in petroleum refining and is employed in certain electrical contacts and specialized filaments. Its high density and creep resistance allow small additions to yield significant improvements in performance.

History and naming: Rhenium was discovered in 1902 by a German team including Walter Noddack, Ida Tacke, and Otto Berg. It was named after the Rhine river (Rhenus in Latin). The element was first isolated in 1925.

Safety: Rhenium compounds can be toxic, and exposure should be minimized. Handling follows standard safety practices for heavy transition metals and their compounds.