Pyrognomic materials are said to become visibly incandescent at relatively low temperatures. In practice, virtually all solid or liquid substances start to visibly incandesce around 798 K (525 °C; 977 °F), with a mildly dull red color, whether or not a chemical reaction takes place that produces light as a result of an exothermic process. This limit is called the Draper point.[1][2][3] The incandescence does not vanish below that temperature, but it is too weak in the visible spectrum to be perceivable.[4] Pyrognomic materials are thought to visibly incandesce at much lower temperatures than the Draper point but a material with this property has never been proven to exist. Allanite and gadolinite are examples of minerals which have been claimed to exhibit true pyrognomic properties but have since been shown to exhibit thermoluminescence.[5][6] The term was originally introduced by the German chemist and mineralogist Theodor Scheerer (1813-1873) in 1840, but the phenomenon had been previously observed by William Hyde Wollaston and Jöns Jacob Berzelius. The term is still used today to describe the thermoluminescence exhibited by various metamict minerals.[7]
References
edit- ^ Draper, John William (1847). "On the Production of Light by Heat". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. Series 3. 30 (202): 345–359. doi:10.1080/14786444708647190.
- ^ Draper, John William (Oct 26, 1878). "Science: Draper's Memoirs". The Academy. 14 (338). London: Robert Scott Walker: 408.
- ^ Mahan, J. Robert (2002). Radiation heat transfer: a statistical approach (3rd ed.). Wiley-IEEE. p. 58. ISBN 978-0-471-21270-6.
- ^ Starr, Cecie (2005). Biology: Concepts and Applications. Thomson Brooks/Cole. ISBN 0-534-46226-X.
- ^ Schwartz K., Lang M. (2016) Mineral Defects. In: White W. (eds) Encyclopedia of Geochemistry. Encyclopedia of Earth Sciences Series. Springer, Cham
- ^ Frondel, Clifford (1958). "Systematic Mineralogy Of Uranium And Thorium" (PDF). Geological Survey Bulletin. 1064. United States Government Printing Office. Retrieved 2024-08-15.
- ^ "Techniques for Collectors : Pyrognomity of minerals".
- Weisstein Encyclopedia
- Theodor Scheerer, Erörterung der plutonischen Natur des Granits und der damit verbundenen krystallinischen Silikate (nach einer Übersetzung von Frapolli) / Discussion sur la nature plutonique du granite et des silicates qui s′y rallient (traduit de l′allemand par L. Frapolli), Bulletin de la Société géologique de France, 2e série, IV, p. 468-498, 1847
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