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Pyrognomic
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. The incandescence does not vanish below that temperature, but it is too weak in the visible spectrum to be perceivable. 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. The term was originally introduced by the German chemist and mineralogist Theodor Scheerer (1813-1873) in 1840, but the phenomenon had been previo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gadolinite
Gadolinite, sometimes known as ytterbite, is a silicate mineral consisting principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula . It is called gadolinite-(Ce) or gadolinite-(Y), depending on the prominent composing element (Y if yttrium predominates, and Ce if cerium). It may contain 35.5% yttria sub-group rare earths, 2.2% ceria earths, as much as to 11.6% BeO, and traces of thorium. It is found in Sweden, Norway, and the US (Texas and Colorado). Characteristics Gadolinite is fairly rare and typically occurs as well-formed crystals. It is nearly black in color and has a vitreous luster. The hardness is between 6.5 and 7 on the Mohs scale, and the specific gravity is between 4.0 and 4.7. It fractures in a conchoidal pattern and streaks grayish-green. It was also thought to exhibit pyrognomic properties, as it can emit visible light when heated to relatively low temperatures, but the scientific consensus is that this is t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allanite
Allanite (also called orthite) is a sorosilicate group of minerals within the broader epidote group that contain a significant amount of rare-earth elements. The mineral occurs mainly in metamorphosed clay-rich sediments and felsic igneous rocks. It has the general formula A2M3Si3O12 H where the A sites can contain large cations such as Ca2+, Sr2+, and rare-earth elements, and the M sites admit Al3+, Fe3+, Mn3+, Fe2+, or Mg2+ among others. However, a large amount of additional elements, including Th, U, Be, Zr, P, Ba, Cr and others may be present in the mineral. The International Mineralogical Association lists four minerals in the allanite group, each recognized as a unique mineral: allanite-(Ce), allanite-(La), allanite-(Nd), and allanite-(Y), depending on the dominant rare earth present: cerium, lanthanum, neodymium or yttrium. Allanite contains up to 20% rare-earth elements and is a valuable source of them. The inclusion of thorium and other radioactive elements in allanit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visible Light
Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz. The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively '' optical radiation''. In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum, and polarization. Its speed in vacuum, , is one of the fundamental constants of nature. All electromagnetic radiation exhibits some properties of both particles and waves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Incandescent
Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electronic, molecular, and lattice oscillations in a material. Kinetic energy is converted to electromagnetism due to charge-acceleration or dipole oscillation. At room temperature, most of the emission is in the infrared (IR) spectrum, though above around 525 °C (977 °F) enough of it becomes visible for the matter to visibly glow. This visible glow is called incandescence. Thermal radiation is one of the fundamental mechanisms of heat transfer, along with conduction and convection. The primary method by which the Sun transfers heat to the Earth is thermal radiation. This energy is partially absorbed and scattered in the atmosphere, the latter process being the reason why the sky is visibly blue. Much of the Sun's radiation transmit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temperature
Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making up a substance. Thermometers are calibrated in various temperature scales that historically have relied on various reference points and thermometric substances for definition. The most common scales are the Celsius scale with the unit symbol °C (formerly called ''centigrade''), the Fahrenheit scale (°F), and the Kelvin scale (K), with the third being used predominantly for scientific purposes. The kelvin is one of the seven base units in the International System of Units (SI). Absolute zero, i.e., zero kelvin or −273.15 °C, is the lowest point in the thermodynamic temperature scale. Experimentally, it can be approached very closely but not actually reached, as recognized in the third law of thermodynamics. It would be impossible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, energy change as new products are generated. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the Atomic nucleus, nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive Chemical element, elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reagent, reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more Product (c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light
Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequency, frequencies of 750–420 terahertz (unit), terahertz. The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively ''optical radiation''. In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity (physics), intensity, propagation direction, frequency or wavelength spectrum, and polarization (waves), polarization. Its speed of light, speed in vacuum, , is one of the fundamental physi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exothermic
In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen). The term ''exothermic'' was first coined by 19th-century French chemist Marcellin Berthelot. The opposite of an exothermic process is an endothermic process, one that absorbs energy, usually in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions where chemical bond energy is converted to thermal energy (heat). Two types of chemical reactions Exothermic and endothermic describe two types of chemical reactions or systems found in nature, as follows: Exothermic An exothermic reaction occurs when heat is released to the surroundings. According to the IUPAC, an exothermic reaction is "a reaction for which the overall stand ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Draper Point
In physics, the Draper point is the approximate temperature above which almost all solid materials visibly glow as a result of black-body radiation. It was established at by John William Draper in 1847. Bodies at temperatures just below the Draper point radiate primarily in the infrared range and emit negligible visible light. The value of the Draper point can be calculated using Wien's displacement law: the peak frequency \nu_\text (in hertz) emitted by a blackbody relates to temperature as follows: \nu_\text = 2.821 \frac, where * is the Boltzmann constant, * is the Planck constant, * is temperature (in kelvins). Substituting the Draper point into this equation produces a frequency of 83 THz, or a wavelength of 3.6 μm, which is well into the infrared and completely invisible to the human eye. However, the leading edge of the blackbody radiation curve extends, at a small fraction of peak intensity, to the near-infrared and far-red (approximately the range 0.7� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermoluminescence
Thermoluminescence is a form of luminescence that is exhibited by certain crystalline materials, such as some minerals, when previously absorbed energy from electromagnetic radiation or other ionizing radiation is re-emitted as light upon heating of the material. The phenomenon is distinct from that of black-body radiation. Physics High energy radiation creates electronic excited states in crystalline materials. In some materials, these states are ''trapped'', or ''arrested'', for extended periods of time by localized defects, or imperfections, in the lattice interrupting the normal intermolecular or inter-atomic interactions in the crystal lattice. Quantum-mechanically, these states are stationary states which have no formal time dependence; however, they are not stable energetically, as vacuum fluctuations are always "prodding" these states. Heating the material enables the trapped states to interact with phonons, i.e. lattice vibrations, to rapidly decay into lower-energy s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Government Publishing Office
The United States Government Publishing Office (USGPO or GPO), formerly the United States Government Printing Office, is an agency of the legislative branch of the United States federal government. The office produces and distributes information products and services for all three branches of the Federal Government, including U.S. passports for the Department of State as well as the official publications of the Supreme Court, the Congress, the Executive Office of the President, executive departments, and independent agencies. An act of Congress changed the office's name to its current form in 2014. History Establishment of the Government Printing Office The Government Printing Office was created by congressional joint resolution () on June 23, 1860. It began operations March 4, 1861, with 350 employees and reached a peak employment of 8,500 in 1972. The agency began transformation to computer technology in the 1980s; along with the gradual replacement of paper with el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theodor Scheerer
Theodor is a masculine given name. It is a German form of Theodore. It is also a variant of Teodor. List of people with the given name Theodor * Theodor Adorno, (1903–1969), German philosopher * Theodor Aman, Romanian painter * Theodor Blueger, Latvian professional ice hockey forward for the Pittsburgh Penguins of the National Hockey League (NHL) * Theodor Burghele, Romanian surgeon, President of the Romanian Academy * Theodor Busse, German general during World War I and World War II * Theodor Cazaban, Romanian writer * Theodor Eicke, German SS general * Theodor Fischer (fencer), German Olympic épée and foil fencer * Theodor Fontane, (1819–1898), German writer * Theodor Geisel, American writer and cartoonist, known by the pseudonym Dr. Seuss * Theodor W. Hänsch (born 1940), German physicist * Theodor Herzl, (1860–1904), Austrian-Hungary Jewish journalist and the founder of modern political Zionism * Theodor Heuss, (1884–1963), German politician and publicist * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
