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Topic: Tungstates

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	Tungsten - LoveToKnow 1911
		A crystalline form was obtained by Debray as olive-green prisms by igniting a mixture of sodium tungstate and carbonate in a current of hydrochloric acid gas, and by Nordenskjold by heating hydrated tungstic acid with borax.
		This salt is obtained by roasting wolfram with sodium carbonate, lixiviating, neutralizing the boiling filtrate with hydrochloric acid and crystallizing at ordinary temperatures.
		The sodium compound was first obtained by Wohler on reducing sodium tungstate with hydrogen; coal-gas, zinc, iron or tin also effect the reduction.
	www.1911encyclopedia.org /Tungsten (2348 words)

	Stukenberg Geology Museum of Kazan State University
		Some molybdates and tungstates accumulates independently being the most important ores of molybdenum and tungsten.
		It is characterized by perfect condition of crystals, their big size, bright diamond shining and orange-red color in the lumps of the Kazan Museum.
		Ca(WO) from many deposits of the world are exhibited in the Mineralogy Section among the most widely spread molibdates and tungstates.
	www.ksu.ru /gmku/eng/s10.php (154 words)

	Process for the manufacture of ammonium and alkali metal tungstates - Patent 4083922
		The ammonium tungstate is believed to be the paratungstate salt, which may be defined as having the formula x(NH.sub.4).sub.2 O.yWO.sub.3.zH.sub.2 O with, for example, x=3 and y=7 or x=5 and y=12, the value of z depending on the conditions of crystallization of the salt.
		The metal tungstate is an iron/manganese tungstate obtained synthetically or as a wolframite ore or concentrate.
		The calcium tungstate is formed by the precipitation of calcium tungstate during the leaching of the tungsten from the reduced huebnerite as a result of the calcium oxide in the huebnerite.
	www.freepatentsonline.com /4083922.html (4858 words)

	Treatment of tri(alkaline earth metal) tungstates with acids - Patent 4083920
		However, tricalcium tungstate is preferably obtained by intimately mixing a tungsten-containing compound, especially scheelite or a wolframite ore or concentrate, with an excess of calcium donor compound (e.g., calcium oxide or calcium carbonate) and heating, (i.e., calcining) at a temperature of 800.degree.-1400.degree.
		It is, therefore, desirable to treat the tricalcium tungstate with acid according to the invention, shortly after formation and/or to protect the tricalcium tungstate from the effects of water until treatment is commenced.
		X-ray diffraction showed that tungsten was in the form of calcium tungstate indicating either incomplete leaching of the tricalcium tungstate in the calcined mixture and subsequent conversion to calcium tungstate during treatment with ammonia or incomplete conversion of the tungstate in the ferberite to tricalcium tungstate.
	www.freepatentsonline.com /4083920.html (4571 words)

	Scintillator compositions of alkali and rare-earth tungstates - US Patent 6585913 (Site not responding. Last check: 2007-10-09)
		In particular, the pyrotungstate is a double tungstate containing an oxide of an alkali metal selected from the group consisting of Na, K, Rb, and Cs and an oxide of a rare-earth element selected from the group consisting of Y, Gd, La, and Lu.
		After firing, the alkali and rare-earth tungstate scintillators of the present invention may be pulverized as disclosed above to produce the scintillator in the powder form which can be pressed into compacted scintillators for use in detectors of X-ray CT systems.
		While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations, equivalents, or improvements therein may be made by those skilled in the art, and are still within the scope of the invention as defined in the appended claims.
	www.patentstorm.us /patents/6585913.html (3205 words)

	Alan Guisewite's Mineral Collection Images: Miscellaneous Systematic Tungstates Page
		These are my tungstates, a small but colorful (and economically important) group of minerals.
		It was once considered to be manganese tungstate, but analyses have shown that there are no WO tetrahedra present.
		Two small light orange scheelites (calcium tungstate) ride on this mixed sulfide matrix with enargite from the Huanzala Mine, Huanuco Department, Peru.
	www.cs.cmu.edu /People/adg/adg-pstimages.html (1005 words)

	Process for improving the adhesion of polymeric materials to metal surfaces - Patent 6383272
		A composition according to claim 1 wherein the adhesion-promoting composition also comprises a source of adhesion enhancing species, which species are selected from the group consisting of molybdates, tungstates, tantalates, niobates, vanadates, isopoly or heteropoly acids of molybdenum, tungsten, tantalum, niobium or vanadium, and combinations of any of the foregoing.
		A composition according to claim 34 wherein the adhesion-promoting composition also comprises a source of adhesion enhancing species, which species are selected from the group consisting of molybdates, tungstates, tantalates, niobates, vanadates, isopoly or heteropoly acids of molybdenum, tungsten, tantalum, niobium, or vanadium, and combinations of any of the foregoing.
		Such sources include alkali metal salts of molybdates, tungstate, tantalates, niobates, vanadates and mixtures thereof such as sodium (or potassium) molybdate, tungstate, niobate or vanadate, and heteropoly acids or isopoly acids of molybdenum, tungsten, tantalum, niobium or vanadium.
	www.freepatentsonline.com /6383272.html (4598 words)

	ELECTROMETRIC STUDIES ON FORMATION OF (Site not responding. Last check: 2007-10-09)
		In view of the interesting results obtained it was considered worthwhile to investigate the composition of barium tungstates obtained by action of Ba on different tungstate anions at specific pH levels by means of electrometric techniques.
		Different tungstates of barium were prepared by mixing solutions of barium nitrate with solutions of sodium molybdate at specific pH levels 8.0, 5.9 and 4.0.
		The formation of barium normal-tungstate in presence of 40% ethanol was found to be almost quantitative and in view of the simplicity, rapidity and accuracy of the titrations, the potentiometric method may be recommended for the determination of barium as tungstate.
	www.sbq.org.br /ranteriores/23/resumos/0878-1 (646 words)

	Inorganic Barrier Layers: Electron Transfer on Mercury Modified by Tungstate Adlayers
		In this communication, we report the tungstate effects on a number of electrode reactions on mercury and present the assumptions concerning possible structures of reaction layers at tungstate-modified surfaces.
		The sensitivity of ET current to tungstate adsorption is essentially higher than that of direct surface tension measurements, and thus presents an instrument of isotherm construction.
		The cathodic limit of this strong inhibition region depends on the ability of a reagent to coadsorb with tungstate, namely, for cationic reagents complete inhibition is hardly possible due to their favorable coadsorption with tungstate anions; for anionic reagents, this limit is more negative, the stronger their adsorption ability.
	www.elch.chem.msu.ru /article/bor1/borz1.htm (2203 words)

	DISORDERED MATERIAL PHYSICS DIVISION
		The luminescence is due to self-trapped exciton on the tungstate sublattice.
		Comparison of luminescence and induced absorption life-time temperature dependencies gives a strong evidence that absorption observed in Ca, Pb, Cd and Zn tungstates is due to electron transition from the luminescence center excited state (exciton) to some upper state.
		The delay between electron-hole creation and exciton formation observed in some tungstates indicates that a large fraction of excitons is not formed directly from band carriers.
	www.cfi.lu.lv /labs/disordered_materials_phys_division.htm (2910 words)

	Chalmers Publications: 575 Tungstate Scintillators Growth, Structures and Properties
		Tungstate crystals are well-known scintillators, which can be used as detector material for high-energy radiation and are often chosen as references in measurements on new luminescent materials.
		Tungstate crystals are excited in the 5-7 eV region by direct optical creation of oxyanion molecular excitons.
		N.B. All bibliographic data in CPL are added by the author or by staff at his/her department.
	publications.lib.chalmers.se /records/full_record/575.html (263 words)

	english.v (Site not responding. Last check: 2007-10-09)
		Research of kinetics process of reduction by carbon of tungstates nickel and cobalt in a temperature interval from 700 up to 10000' is lead.
		Isothermal models of reduction by carbon tungstates cobalt and nickel are simulated.
		The sequence of growth of phases is investigated and the equations of speed of reactions at separate stages of process are described.
	zhurnal.ape.relarn.ru /articles/2004/216.html (178 words)

	Tungstate and Molybdate Minerals (from mineral) -- Britannica Student Encyclopedia
		Tungsten, a metal used in the manufacture of electric light bulbs, steel alloys, and magnets, is obtained chiefly from two minerals.
		These are scheelite, or calcium tungstate, and wolframite, which is a mixed tungstate of the elements manganese and iron.
		More results on "Tungstate and Molybdate Minerals (from mineral)" when you join.
	www.britannica.com /ebi/article-204724 (796 words)

	Search Results for tungstate - Encyclopædia Britannica
		Tungsten bronze, composed of tungstates of the alkali and alkaline-earth metals, is employed as a substitute for bronze in ornamental paints.
		Sodium tungstate is also used to produce phosphotungstic...
		Tungsten in one of its mineral forms was given its name (meaning “heavy stone”) by the Swedish mineralogist A.F. Cronstedt in 1755.
	www.britannica.com /search?query=tungstate&submit=Find&source=MWTEXT (288 words)

	AllRefer.com - tungsten, Compound & Element (Compounds And Elements) - Encyclopedia
		), or wolframic acid, which is the basis of a series of salts called tungstates, or wolframates.
		Tungsten is usually added to steel in the form of ferrotungsten, obtained by the reduction of ferrous tungstate in an electric furnace.
		Tungsten carbide is used in place of diamond for dies and as an abrasive.
	reference.allrefer.com /encyclopedia/T/tungsten.html (438 words)

	Tungstates (Site not responding. Last check: 2007-10-09)
		The chemistries of the Tungstate ion (WO4) 2-, and the Molybdate ion (MoO4) 2-, are so similar that the groups of minerals are always associated, with extensive solid solution between the two extremes.
		Tungstates are very important industrial minerals giving rise to Tungsten metal which when alloyed with iron, produces a very strong corrosion resistant steel.
		The metal is also extensively used in the manufacture of filaments for light-bulbs, vacuum and x-ray tubes.
	www.wildaboutrocks.com /category15_1.htm (356 words)

	Mineralogy - Tungstates and Molybdates
		Tungstates and Molybdates - Salts of tungstic acid and molybdic acid are respectively called tungstates and molybdates.
		These are scheelite, or calcium tungstate, and wolphramite, which is a mixed tungstate of the elements manganese and iron.
		Tungstates and Molybdates: Common Tungstate and Molybdate Minerals
	l2l.port5.com /s_geol/mnr_tung.html (546 words)

	Journal of Materials Research 2001
		The high degree of mixing of W and Cu phases in copper tungstates makes them an attractive source for manufacturing W-Cu composite powders.
		Hydrogen reduction of copper tungstates provides composite W-Cu powder products with a uniform, homogeneous dispersion of the metal phases.
		Hydrated, dehydrated, and complex oxides of tungsten and copper have been used as solid reactants.
	lucy.mrs.org /publications/jmr/jmra/2001/apr/026.html (124 words)

	Publications
		Reduction of tungstates in hydrogen plasma leads to production of tungsten powder with high sintering activity.
		Very interesting is though the behavior of substances originating from the reaction of plasma with cationic part of tungstates.
		Besides of the amonium tungstate also sodium-, calcium- and lead- tungstates were studied.
	www.muni.cz /research/publications/599325 (406 words)

	Optical Spectroscopy and Stimulated Emission of Dysprosium-doped Tungstates (Site not responding. Last check: 2007-10-09)
		Rare-earth ion-doped tungstate materials have been intensively investigated for laser development for lidar applications.
		The tungstate materials in many different compositions have a large x(3) Raman scattering effect and can be used in various laser experiments and developments.
		We are currently interested in the development of a visible laser, which can be doubled to the 270-320 nm for the remote sensing of ozone in the atmosphere.
	flux.aps.org /meetings/YR01/APR01/abs/S1500062.html (192 words)

	Tungsten Applications - Chemical Processes
		Another example of catalytically active tungsten compounds is superfine tungsten carbide, mostly prepared by thermal decomposition of organic substances in the presence of a suitable tungsten compound.
		For the manufacture of chemical products, commercially available tungsten compounds such as sodium tungstate, ammonium tungstates, tungstic oxide or tungstic acid are commonly used as raw materials.
		Barium and zinc tungstate are examples for bright white pigments.
	www.azom.com /details.asp?ArticleID=1260 (458 words)

	WOLFRAMITE, or WOLFRAM - Online Information article about WOLFRAMITE, or WOLFRAM
		steel and in the preparation of certain tungstates.
		sodium tungstate, which was easily removed as a soluble See also:
		Thus there is a manganous tungstate (MnWO4) known as hi bnerite, a name given by E. Riotte, in 1865, in compliment to Adolph Hiibner, a Saxon mineralogist.
	encyclopedia.jrank.org /WIL_YAK/WOLFRAMITE_or_WOLFRAM.html (622 words)

	QUT \| ePrints Archive - Microwave assisted synthesis of divalent metal tungstate minerals: ferberite, ...
		A variety of metal tungstates have been synthesised in a microwave assisted oven at 100 and 150°C and corresponding autogenous water vapour pressure within a time frame of 30 minutes to 2 hours.
		The Raman spectra are consistent with those reported for the natural equivalents of these tungstates.
		The lead tungstate ν1(Ag) mode is observed at 904 cm-1, while the ν2(Ag) vibration is observed as a strong band at at 326 cm-1 accompanied by a weak ν2(Bg).
	eprints.qut.edu.au /archive/00000798 (281 words)

	L923-L926 (Site not responding. Last check: 2007-10-09)
		Efficient high-order Stokes and anti-Stokes generation in the visible and near infrared (NIR) in monoclinic KDy(WO and KLu(WO 1aser host crystals by stimulated Raman scattering (SRS) and Raman-induced four-wave mixing (RFWM) were observed at 300 K for the first time in the single-pass geometry under picosecond excitation.
		All scattering components were identified and connected with the SRS-active vibration modes of these tungstates.
		All authors are working in cooperating with Joint Open Laboratory for Laser Crystals and Precise Laser Systems at the Institute of Crystallography and the Institute of Laser Physics, the Russian Academy of Sciences.
	jjap.ipap.jp /link?JJAP/37/L923 (520 words)

	Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc2(WO4)3-Type Structure
		To realize a trivalent ion conduction in solids, the Sc -type structure was chosen on the basis of the mobile trivalent ions and the structure which reduces the electrostatic interaction between the framework and the mobile trivalent ionic species as much as possible.
		The typical conductivity of the rare earth tungstates R
		Furthermore, by the dc electrolysis, the mobile species was clarified to be the rare earth ions Sc and Y
	pubs.acs.org /cgi-bin/abstract.cgi/cmatex/1998/10/i07/abs/cm980157e.html (263 words)

	Welcome to DT-CRYS (Site not responding. Last check: 2007-10-09)
		The main objectives of WP1 are (i) to find the optimum growth methods and conditions for reproducible and high-quality growth of the double tungstate crystals (undoped, doped, co-doped and stoichiometric) and (ii) the structural, optical, spectroscopic and magnetic characterization of the grown samples.
		This assessment is to provide important knowledge about application-relevant parameters of known double tungstates and new information on materials and structures grown for the first time.
		At FEE, also the growth of Yb-doped double tungstates on inert hosts in segment form will be attempted in order to directly obtain monolithic composites.
	www.dt-crys.net /wp1.html (277 words)

	Timerock Fossils, Minerals & Crystals - Mineral Types - Tungstates
		The following list includes the most significant minerals which occur in nature as tungstates.
		To view the properties of an element, select it from the list and click the "GO" button.
		Click on an item to view details and, if you wish, bid.
	www.timerock.com /timerock/library/minerals/mineral_tungstates.asp (81 words)

	Tungstates Encyclopedia Article, Definition, History, Biography (Site not responding. Last check: 2007-10-09)
		Looking For tungstates - Find tungstates and more at Lycos Search.
		Find tungstates - Your relevant result is a click away!
		Look for tungstates - Find tungstates at one of the best sites the Internet has to offer!
	www.karr.net /encyclopedia/Category:Tungstates (107 words)

	Introduction to Tungsten (Site not responding. Last check: 2007-10-09)
		Calcium and magnesium tungstates are widely used in fluorescent lighting; other salts of tungsten are used in the chemical and tanning industries.
		Tungsten disulfide is a dry, high-temperature lubricant, stable to 500C.
		Calcium and magnesium tungstates are widely used in fluorescent lighting; other salts of tungsten are used in the chemical and tanning industries.Tungsten disulfide is a dry, high-temperature lubricant, stable to 500C.
	chinatungsten.com /chwurl-2-1.htm (1241 words)

	Berzelian Classification System (Site not responding. Last check: 2007-10-09)
		The antimonides, arsenides, selenides, and tellurides closely resemble the sulfides in composition, while the chromates, molybdates and tungstates resemble the sulfates.
		Species of the molybdate and tungstate classes are typically heavy, soft, and brittle.
		Minerals containing the molybdate or tungstate anion groups are categorized as members of the molybdate or tungstate classes.
	dave.ucsc.edu /myrtreia/Berzelian_class.html (7720 words)

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