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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.
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.
This is a list of the various reported boiling points for the elements, with recommended values to be used elsewhere on Wikipedia. ... 613 °C: 34 Se selenium ...
Tin(II) selenide can be formed by combining the elements tin and selenium above 350 °C. [13] Problems with the composition are encountered during synthesis. Two phases exist—the hexagonal SnSe 2 phase and the orthorhombic SnSe phase. Specific nanostructures can be synthesized, [14] but few 2D nanostructures have been prepared. Both square ...
6 C carbon; use: WEL ... 34 Se selenium; use: 95.48 CRC: 95.48 ... Values refer to the enthalpy change in the conversion of liquid to gas at the boiling point (normal ...
Selenium is a nutrient that is naturally present in many foods, added to others and is also available as a dietary supplement in pill, powder and liquid form, explains Perri Halperin, a ...
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]
A stoichiometric mixture of elemental bismuth and selenium, when heated above the melting points of these elements in the absence of air, will become a liquid that freezes to crystalline Bi 2 Se 3. [27] Large single crystals of bismuth selenide can be prepared by the Bridgman–Stockbarger method. [28]