Tungsten sodium tungstate

Tungsten Sodium tungstate solution at pH 2 High-molecular weight amine extractant in kerosene mixer-settler system... 

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

A considerable difference in the toxicity of soluble and insoluble compounds of tungsten has been reported (58). For soluble sodium tungstate,... 

Orally in rats, the toxicity of sodium tungstate was highest, tungsten trioxide was intermediate, and ammonium tungstate [15855-70-6] lowest (59,60). In view of the degree of systemic toxicity of soluble compounds of tungsten, a threshold limit of 1 mg of tungsten per m of air is recommended. 

Sodium tungstate is used in the manufacture of heteropolyacid color lakes, which are used in printing inks, plants, waxes, glasses, and textiles. It is also used as a fuel-ceU electrode material and in cigarette filters. Other uses include the manufacture of tungsten-based catalysts, for fireproofing of textiles, and as an analytical reagent for the deterrnination of uric acid. 

With regard to the use of tungsten-based systems, Payne and Williams reported on the selective epoxidation of maleic, fumaric, and crotonic acids with a catalytic amount of sodium tungstate (2mol%) in combination with aqueous hydrogen... 

The constancy of the quotient in the last line of Table 7-2 is greatly improved over that in the line above the last, proving that Equation 7-5 holds. So far as we know, this is the first case in which the absorption effects for a series of solutions have been obtained so precisely. Examples of this kind place on a firmer basis the calculation of semiquantitative analytical results from measured intensities when the composition of the matrix (all of S but E, the element sought) in a sample is approximately known. For example, tungsten contents could be estimated from measurements of L7I intensity for sodium tungstate solutions even when other salts are present in the absence of such salts, tungsten contents... 

Recent results from the authors laboratory69 on the x-ray emission spectrography of tungsten or molybdenum in solution illustrate some of the points made in Section 7.13. The also show the usefulness of internal standards (7.12). Finally, the work on tungsten is closely related to the experiments on the absorption effect in sodium tungstate solutions, the results of which are summarized in Table 7-2. 

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 ... 

Sodium tungstate is crystallized, separated from any impurities in the solution, and digested again with hydrochloric acid to form tungstic acid in purified form. The pure acid is dried, ignited and reduced with carbon to form tungsten powder from which most non-ferrous alloys are made. 

If tungsten is recovered from the wolframite group mineral, the wolframite concentrate is boiled or pressure-digested with 50% caustic soda solution. Alternatively, they may be fused or sintered with caustic soda, caustic potash or sodium carbonate and the fused mass then leached with water. The solution is filtered to separate sodium tungstate solution. The fdtrate is subjected to various treatments to remove molybdenum, phosphorus, and arsenic impurities. The filtrate at this point is essentially a solution of sodium tungstate and is treated in the same way as that obtained from the scheehte concentrate discussed above. 

Tungstic acid is obtained as an intermediate in the recovery of tungsten from its minerals, scheebte and wolframite (See Tungsten). Also, the tungstic acid may be prepared by heating sodium tungstate with sulfuric acid or hydrochloric acid ... 

Thiosalts and Sulphides of Molybdenum and Tungsten. Pour 2-3 ml of an ammonium molybdate solution into one test tube and 2-3 ml of a sodium tungstate solution into another one. Add 2-3 drops of a 25 % ammonia solution to each solution and pass a stream of hydrogen sulphide through them from a Kipp gas generator. What compounds form Acidify the solutions with a 10% hydrochloric... 

Reduction of MoIybdenum(VI) and Tungsten VI) Compounds. Pour 3 ml of an ammonium molybdate solution into each of four test tubes, acidify with a 2 N hydrochloric acid solution, and heat up to boiling. Add solutions of sulphuric acid, hydrogen sulphide, and tin(Il) chloride to three of the tubes, respectively, and throw one or two small pieces of zinc into the last tube. Perform similar experiments using sodium tungstate as the initial reactant. Write the equations of the reactions. 

Molybdenum and Tungsten Peroxide Compounds. Pour ammonium molybdate and sodium tungstate solutions into separate test tubes, acidify them with sulphuric acid, and add several drops of a 1 % hydrogen peroxide solution to each tube. How does the colour of the solutions change Write the equations of the reactions. 

Trichloroisopropoxytitanium, 300 Trichloromethyltitanium, 216 Triisopropoxymethyltitanium, 213 Triisopropoxy[ l-(trimethylsilyl)-l, 2-bu-tadienyljtitanium, 218 Tungsten Compounds /rans-Bromotetracarbonyl(methyl-methylidyne)tungsten, 49 Hydrogen peroxide-Sodium tungstate, 145... 

Sodium tungstate, 145 Tungsten carbonyl, 49 Vanadium Compounds Alkynylvanadium(III) chloride,... 

Amine salts have been used for more than 25 years in the manufacture of pure ammonium paratungstate from sodium tungstate solutions obtained from the leaching of tungsten ores with alkali.211 Such solutions are produced by the leaching of scheelite with sodium carbonate solution at 190 to 225 °C... 

In a typical solvent-extraction process,211 the pH value of the sodium tungstate solution is adjusted to about 2.5 with sulfuric acid, and the tungsten is extracted into a 7% solution of the tertiary amine Alamine 336 plus 7% isodecanol in kerosene in two countercurrent stages at a temperature of 50 °C. Distribution data are consistent with the extraction of species such as H2W1204o6 and Wi2O408- in reactions of the type208-212... 

Tungsten ores are concentrated by mechanical and magnetic processes and the concentrates attacked by fusion with NaOH. The cooled melts are leached with water, giving solutions of sodium tungstate from which hydrous W03 is precipitated on acidification. The hydrous oxide is dried and reduced to metal by hydrogen. 

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