Sodium tungstate, preparation

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

Refer the readings to a calibration curve prepared from a solution containing spectrographically pure iron to which suitable amounts of standard sodium tungstate solution have been added. 

One problem associated with the peroxotungstate-catalyzed epoxidation system described above is the separation of the catalyst after the completed reaction. To overcome this obstacle, efforts to prepare heterogeneous tungstate catalysts have been conducted. De Vos and coworkers employed W catalysts derived from sodium tungstate and layered double hydroxides (LDH - coprecipitated MgCU, AICI3, and NaOH) for the epoxidation of simple olefins and allyl alcohols with... 

Tetrahydrobenzyl alcohol (( )3-cyclohexenene-l-methanol) and 30% aqueous hydrogen peroxide were purchased from Fluka, AG. 3-Cyclohexene-1-carboxylic acid and cis-4-cyclohexene-l,2-dicarboxylic acid were used as purchased from Lancaster Chemical Co. Methyl iodide, acetic anhydride, Oxone (potassium peroxymonosulfate), Aliquot 336 (methyl tri-n-octylammonium chloride), sodium tungstate dihydrate and N,N-dimethylaminopyridine (DMAP) were purchased from Aldrich Chemical Co. and used as received. 3,4-Epoxycyclohexylmethyl 3, 4 -epoxycyclohexane carboxylate (ERL 4221) and 4-vinylcyclohexene dioxide were used as purchased from the Union Carbide Corp. (4-n-Octyloxyphenyl)phenyliodonium hexafluoroantimonate used as a photoinitiator was prepared by a procedure described previously (4). 

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 ... 

The Falin-Ciocalteu reagent (FCR) is a complex formed in a reaction between sodium tungstate and sodium molybdenate in hydrochloric add and phosphoric acid, which turns yellow after lithium sulphate is added. The reagent reads in an alkaline environment with reducing compounds. Such a reaction gives a blue chromophore which is observed by colorimetry. The Folin-Ciocalteu method is highly sensitive - both to phenolic and non-phenolic compounds, e.g. proteins, vitamin C, vitamin Bj, folic acid, Cu(I). The method is applied most frequently to determine the total content of phenolic compounds [34,35]. If that is the case, a sample for determination should be prepared in a proper manner to minimise the effect of non-phenolic... 

The oxidation of fumaric acid with hydrogen peroxide in the presence of sodium tungstate was used to prepare this intermediate and the product isolated in 60% yield. 

Prepare a solution of sodium tungstate containing 0.5 g of the dry salt, and pour into it an equal volume of a 10% hydrochloric acid solution. Wash the precipitate by decantation with water slightly acidified with hydrochloric acid. 

Silicotungstic acid is prepared by the hydrolysis of a mixture of sodium tungstate and sodium silicate. This reaction goes to completion only in the presence of acid. Sulfuric, acetic, and nitric acids all have been used,1,213 but none of them is completely satisfactory. Sulfuric acid, since it cannot be volatilized from the silicotungstic acid, is apt to cause decomposition. It also tends to precipitate... 

Cyclic nitrones have been prepared by the oxidation of 3,4-dihydroisoquinolines using sodium tungstate (2) as illustrated in Eq. 2. Spiro nitrones, (II), have also been prepared using this method. 

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