Tungstenic phosphoric acid

Polyamides (nylons) Formalin/osmium tetroxide Tungsten phosphoric acid/osmium tetroxide Ruthenium tetroxide... 

I2/K2C03, tetrabutylammonium hydroxide, tungsten phosphoric acid, ionic liquids, reactions in water, solvent-free conditions, microwave promoted reactions, reactions promoted by phase-transfer catalysts, and finally, for some very reactive substrates, uncatalyzed reactions. " Unfortunately for the practicing chemist, few of these conditions are well worked out enough or understood well enough to have become common, and almost all examples of the Knoevenagel condensation in the literature employ an amine base, or a salt thereof (Cope conditions, or amino acid catalysis) or TiCl4/Base(Lehnert conditions). ... 

A 3/8 inch diameter aluminum or titanium-tungsten dot pattern WLs fabricated on top of the cured polyimide film to make electrical leakage to substrate measurements for pinhole density estimation. An etch decoration technique was used to visually determine pinhole densities in polyimide films. The polyimide film was cast on substrates comprised of a layer of 200 nm thick alumimmi on blue colored field oxide with a grid pattern for area computation. Replicate holes were etched in the aluminum by a hot phosphoric acid solution. With the polyimide film removed, a good visual contrast was achieved for pinhole density counting. 

It is no doubt on account of this formation of complexes that concentrated phosphoric acid is capable of dissolving such inert metals as tungsten and zirconium, as well as silicon and carborundum.8 The less noble metals are attacked by phosphoric acid, but iron tends to become passive.9 The basic oxides, ferric oxide and alumina are dissolved by the concentrated acid.6... 

The reactivity of tungsten oxide is also slightly increased after it mechanical activation. In the case of activated WO3, 10 % of oxide reacts with the solution of phosphoric acid, while in the case of activated WO3 -V2O5 mixtures, the yield increases up to 13 %. 

The reaction of u-butenes to give isobutylene is cataly zed by a wide variety of solid acids but requires relatively high temperature. Typical catalysts include alumina, halogenated alumina, amorphous silica-alumina, supported phosphoric acid, and supported tungsten or molybdemmi oxide. The most characteristic features of the skeletal isomerization of n-butenes... 

Solutions of tungstates containing ammonium sulphide yield with hydrochloric acid a brown j recipitate of tungsten trisulphide. The addition of zinc chloride to a tungstate solution produces a yellow precipitate which becomes blue on warming with dilute hydrochloric or sulphuric acid. When excess of hydrochloric acid is added to a solution of alkali tungstate and the mixture reduced by means of zinc, brilliant colours, from red to blue, are produced if phosphoric acid is used, a fine blue precqntate results. 

Tungsten Subphosphide, W4P3.—By strongly heating a mixture of phosphoric acid and tungstic anhydride in a carbon crucible, lustrous steel-coloured crystals of this phosphide are obtained. The crystals are si.x-sided prisms of density 5-21. It conducts electricity well, is very" stable in air even at higher temperatures, and is very resistant to acids. When heated in a current of oxygen it bums brilliantly. It dissolves in a fused mixture of alkali carbonate and nitrate. 

O. Savadogo, P. Beck, Five percent platinum-tungsten oxide-based electrocatalysts for phosphoric acid fuel cell cathodes. J. Electrochem. Soc. 1996, 143(12), 3842-3846. 

Phosphoric acid concentrated (H3PO4). Tungsten shows a slight attack depending on temperature and time. 

Phosphoric acid (H3PO4). Tungsten is highly resistant to diluted phosphoric acid as long as air is excluded. It dissolves easily in concentrated acid. 

Extraction of the molybdenum complex with a-benzoinoxime (formula 31.1) into CHCI3, from 0.01-2 M HCl is a selective method for separating molybdenum [1 ]. Under the conditions employed in the extraction of the molybdenum a-benzoinoxime complex Mo, Mo02(C 4H 202N)2, only W, V, Cr, and Pd are also extracted. Tungsten and vanadium are not extracted in the presence of phosphoric acid and Fe(II). 

Some processes use dUvie acid under high pressures/ an increased yield of alcohol being obtained with a corresponding decreased yield of ether. The jdeld of ether may be also decreased by removal of alcohol from contact with unreacted sulfate liquor, as rapidly as it is formed, by immediate distillation in hot water. Brooks and others have shown the advantages of absorption of ethylene under pressure. Various catalysts are used in these processes, and ethyl alcohol has also been prepared by the direct combination of ethylene with water in the presence of catalysts and under pressure. The two most promising catalysts are supported phosphoric acid and promoted tungsten oxide. ... 

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