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The minimum distance between chains is 343.6 pm. Gray selenium is formed by mild heating of other allotropes, by slow cooling of molten selenium, or by condensing selenium vapor just below the melting point. Whereas other selenium forms are insulators, gray selenium is a semiconductor showing appreciable photoconductivity.
Spectral lines of selenium: Other properties; ... phase comment = | melting point K = | melting point C = | melting point F = | melting point ref = | melting point ...
The Gmelin rare earths handbook lists 1522 °C and 1550 °C as two melting points given in the literature, the most recent reference [Handbook on the chemistry and physics of rare earths, vol.12 (1989)] is given with 1529 °C.
Selenium is a soft (MH 2.0) ... The ordinary metals have lower melting points and cohesive energies than those of the transition metals. [214] Gray [215] ...
Melting point: 611 °C (1,132 °F; 884 K) Structure ... The compound may be formed by the reaction of antimony with selenium and has a melting point of 885 K. [4]
Melting point: 340 °C (644 °F; 613 K) (sealed tube) Boiling point: 350 °C (662 °F; 623 K) subl. ... Selenium dioxide is the chemical compound with the formula SeO 2.
Selenium is toxic in high concentrations. As sodium selenite, the chronic toxic dose for human beings was described as about 2.4 to 3 milligrams of selenium per day. [7] In 2000, the US Institute of Medicine set the adult Tolerable upper intake levels (UL) for selenium from all sources - food, drinking water and dietary supplements - at 400 μg/day. [8]
Hydrogen selenide is hazardous, being the most toxic selenium compound [3] and far more toxic than its congener hydrogen sulfide. The threshold limit value is 0.05 ppm. The gas acts as an irritant at concentrations higher than 0.3 ppm, which is the main warning sign of exposure; below 1 ppm, this is "insufficient to prevent exposure", while at ...