Phosphoric spar

Edmond Becquerel (1820-1891) was the nineteenth-century scientist who studied the phosphorescence phenomenon most intensely. Continuing Stokes s research, he determined the excitation and emission spectra of diverse phosphors, determined the influence of temperature and other parameters, and measured the time between excitation and emission of phosphorescence and the duration time of this same phenomenon. For this purpose he constructed in 1858 the first phosphoroscope, with which he was capable of measuring lifetimes as short as 10-4 s. It was known that lifetimes considerably varied from one compound to the other, and he demonstrated in this sense that the phosphorescence of Iceland spar stayed visible for some seconds after irradiation, while that of the potassium platinum cyanide ended after 3.10 4 s. In 1861 Becquerel established an exponential law for the decay of phosphorescence, and postulated two different types of decay kinetics, i.e., exponential and hyperbolic, attributing them to monomolecular or bimolecular decay mechanisms. Becquerel criticized the use of the term fluorescence, a term introduced by Stokes, instead of employing the term phosphorescence, already assigned for this use [17, 19, 20], His son, Henri Becquerel (1852-1908), is assigned a special position in history because of his accidental discovery of radioactivity in 1896, when studying the luminescence of some uranium salts [17]. 

Use Phosphor. Iceland spar is used in optical instruments. 

Acid-spar AI3-01166 Calcium difluoride Calcium fluoride Calcium fluoride (CaFa) EINECS 232-188-7 Fluorite Fluorspar HSDB 995 Irtran 3 Liparite Met-spar Natural fluorite. Source of fluorine, flux, ceramics, phosphors, paint pigment, catalyst in vrood preservative, spectroscopy, electronics, lasers, high-temperature dry-film lubricants. Solid mp = 1403° bp = 2500° d = 3.18 insoluble in H2O LD50 (gpg orl) > 5 g/kg. Cerac G Silicones Noah Chew. Solvay Deutschland GmbH. 

Long needles from cone. HHO3. M.p. 190° (195-6°). Sol. hot EtOH, hot cone. HNO3. Spar. sol. cold EtOH. Insol. HgO. Forms a ydride at 230°. Soda-lime fusion —y phosphoric acid -4- benzene. 

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