Tungsten hydroxide

A hydrosol of tungsten hydroxide is readily produced by the electrolysis of a 2 per cent, solution of sodium tungstate between a mercuiy cathode and a silver anode in a Hildebrand cell. The solution must not be allow ed to become acid, or blue compounds are produced. The hydrosols obtained in this way are clear and transj arent but brown in colour. The addition of potassium chloride causes coagulation, a black powder, resembling the lower oxides of tungsten, being formed. ... 

Usually WOj/Zr02 catalysts are synthesized by co-precipitation of zirconium and tungsten hydroxides or by impregnation of dried zirconium hydroxide with ammonium meta-tungstate solution with subsequent calcining of samples at 700-800°C [1-6]. However the samples so obtained possess relatively low surface area (40-60 m /g). 

Sodium tungsten hydroxide oxide phosphate 3334 Solcain 2237... 

Ethylamino)-3-ethylimino-2,7-dimethyl-3H-xanthene-9-yl) benzoic acid, ethyl ester with molybdenum tungsten hydroxide oxide phosphate. See Pigment red 81... 

Molybdenum tungsten hydroxide oxide phosphate, compd. with ethyl 2-(6-ethylamino)-3-(ethylimino)-2,7-dimethyl-3H-xanthen-9-yl) benzoate. See Pigment red 81 Molybdenum white. See Calcium-zinc-molybdenum complex Zinc molybdate Molybdic acid, ammonium salt, tetrahydrate. 

Synonyms Cl 45160 lake 9-(2-Ethoxycarbonyl) phenyl-3,6-bis (ethylamino)-2,7-dimethylxanthylium molybdatetungstatephosphate 2-((6-Ethylamino)-3-ethylimino-2,7-dimethyl-3H-xanthene-9-yl) benzoic acid, ethyl ester with molybdenum tungsten hydroxide oxide phosphate Molybdenum tungsten hydroxide oxide phosphate, compd. with ethyl 2-(6-ethylamino)-3-(ethylimino)-2,7-dimethyl-3H-xanthen-9-yl) benzoate Molybdotungstophosphoric acid, compd. with ethyl 2-(6-(ethylam i no)-3-(ethyl i m i no)-2,7-dimethyl-3H-xanthen-9-yl) benzoate Empihcal C28H31N2O3 x (unspecified)... 

Anhydrous sodium tungstate, Na2W04, is prepared by fusing tungsten trioxide in the proper proportion with sodium hydroxide or sodium carbonate ... 

Tantalum-Tungsten Braun, Sedlatschek and Kieffer examined tantalum-tungsten alloys in 50% potassium hydroxide up to 80°C and in 20% hydrochloric acid at 20°C. In the alkaline solution the corrosion rate was a maximum when the tantalum was over 60 at.%. In hydrofluoric acid the alloy system exhibited the relatively low corrosion rates associated with tungsten until the tantalum concentration exceeded 80 at.%. 

Table 7-8. Determination of Tungsten in Sodium Hydroxide Solution...

Tungsten trioxide, WO j, by virtue of its high melting point (1473 K) and insolubility in neutral water and concentrated mineral acids, places it well within the confines of ceramic materials. However, a large branch of inorganic chemistry opens up for W03 when it is exposed to alkali. WO3 can be dissolved in aqueous sodium hydroxide solution to produce sodium tungstate, Na2W04 ... 

Molybdenum oxidizes at high temperatures but not at room temperatures. It is insoluble in acids and hydroxides at room temperatures. At room temperatures, all three metals (chromium, molybdenum, and tungsten) resist atmospheric corrosion, which is one reason chromium is used to plate other metals. They also resist attacks from acids and strong alkalis, with the exception of chromium, which, unless in very pure form, will dissolve in hydrochloric acid (HCl). 

However, the enzymology of alkene and alkyne hydration is not well known. Recently, Meckenstock et al. (1999) discovered that the enzyme responsible for anaerobic hydration of acetylene contains a tungsten atom and an [Fe-S] cluster. This may hint that the enzyme uses the tungsten as a Lewis acid to activate the double bond. Possibly, the [Fe-S] cluster then serves to deliver a hydroxide as known in many common metabolite hydrations (Flint and Allen, 1996). Having introduced an oxygen moiety in an initial hydration, anaerobic bacteria may now be able to continue the biodegradation of such compounds. 

Instead of lixiviating with water, the pyrosulphate fusion is followed in a recent process 7 by extraction with tartaric acid solution the insoluble residue contains silica, tin, and lead, and the solution, after being saturated with hydrogen sulphide for the precipitation of copper, antimony, etc., contains the hydroxides of niobium and tantalum as well as tungsten, titanium, zirconium, rare earth metals, etc. 

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