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Scheelite is a calcium tungstate mineral with the chemical formula Ca W O 4. It is an important ore of tungsten (wolfram). Scheelite is originally named after Swedish chemist Carl Wilhelm Scheele (1742–1786). Well-formed crystals are sought by collectors and are occasionally fashioned into gemstones when suitably free of flaws.
In chemistry, a tungstate is a compound that contains an oxyanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is WO 2− 4 , "orthotungstate". [ 1 ] Many other tungstates belong to a large group of polyatomic ions that are termed polyoxometalates , ("POMs"), and specifically termed isopolyoxometalates as they ...
4 or calcium tungstate: exhibits long decay time 9 μs and short wavelength emission with maximum at 420 nm matching sensitivity curve of bi‑alkali PMT. [7] The light yield and energy resolution of the scintillator (6.6% for 137 Cs) is comparable with that of CdWO 4. [53]
Powellite (calcium molybdate) and scheelite (calcium tungstate) fluoresce intrinsically in yellow and blue, respectively. When present together in solid solution , energy is transferred from the higher-energy tungsten to the lower-energy molybdenum , such that fairly low levels of molybdenum are sufficient to cause a yellow emission for ...
He invented a fluorescent lamp in 1896 that used a coating of calcium tungstate as the fluorescing substance, excited by X-rays. Although it received a patent in 1907, [6] it was not put into production. As with a few other attempts to use Geissler tubes for illumination, it had a short operating life, and given the success of the incandescent ...
Sodium tungstate and lead have been studied for their effect on earthworms. Lead was found to be lethal at low levels and sodium tungstate was much less toxic, but the tungstate completely inhibited their reproductive ability. [131] Tungsten has been studied as a biological copper metabolic antagonist, in a role similar to the action of molybdenum.
Thomas Alva Edison identified the blue-emitting calcium tungstate (CaWO4) as a suitable phosphor, which quickly became the standard for X-ray intensifying film. In the 1970s, calcium tungstate was replaced by even better and finer intensifying films with rare earth-based phosphors (terbium-activated lanthanum oxybromide, gadolinium oxysulfide ...
Tungstate minerals contain tungsten in the anion group WO 4 2−. Pages in category "Tungstate minerals" The following 10 pages are in this category, out of 10 total.