Phosphotungstic acid, precipitation

The separation and estimation of the two main groups of amino acids can be carried out in one experiment, instead of separately as described. The protein is hydrolysed by sulphuric acid, the tyrosine, cystine and diaminotrioxydodecanic acid are removed by crystallisation, and the diamino acids are precipitated by phosphotungstic acid. From this precipitate they are obtained by decomposition with baryta, and they are then separated by means of their silver compounds by Kossel, Kustcher and Patten s method. The filtrate from the phosphotungstic acid precipitate is freed from the excess of phosphotungstic acid by means of baryta, and the solution is treated by Fischer s ester method for the monoamino acids. 

For cesium, the waste packaging process calls for the separation of the cesium from the acid waste, purification to remove metallic contaminants, conversion to anhydrous chloride, and subsequent encapsulation in double-walled metal cans. The cesium currently is separated from the acid waste by phosphotungstic acid precipitation and partially purified... 

Tannic acid, phosphomolybdic acid, and phosphotungstic acid precipitate peptones. Most of the acid aniline dyes and many of the organic color bases also precipitate proteins. 

An examination of the phosphotungstic acid precipitate showed that it contained several products of a complex nature. From them a substance was isolated which consisted of two molecules glycine, one... 

Cesium isotopes can be recovered from fission products by digestion in nitric acid, and after filtration of waste the radioactive cesium phosphotungstate is precipitated using phosphotungstic acid. This technique can be used to prepare radioactive cesium metal or compounds. Various processes for removal of Cs isotopes from radioactive waste have been developed including solvent extraction using macrocycHc polyethers (62) or crown ethers (63) and coprecipitation with sodium tetraphenylboron (64). 

In biological materials, various nonspecific precipitants have been used in the gravimetric deterrnination of choline, including potassium triiodide, platinum chloride, gold chloride, and phosphotungstic acid (28). Choline may also be determined spectrophotometricaHy and by microbiological, enzymatic, and physiological assay methods. 

Only in a few cases has this compound been isolated from the products of hydrolysis of proteins, since its separation is extremely laborious. It can only be effected after all the other amino acids have been removed by crystallisation and by the ester method, and after the diamino acids have been precipitated by phosphotungstic acid. From the last mother-liquors it is obtained by crystallisation, and is best identified in the form of its /8-naphthalene sulpho-derivative. 

The separation and estimation of the three compounds—arginine, histidine, lysine—is carried out by the method described by Kossel and Kutscher in 1900, which was slightly modified in 1903 by Kossel and Patten. It is based upon the earlier work of Drechsel, Hedin and Kossel, and depends upon the precipitation of arginine and histidine as their silver salts, and of lysine by phosphotungstic acid, and then by picric acid. 

When 5% phosphotungstic acid was used as the precipitant agent in cheeses, the soluble fraction consisted only of amino acids and low-molecular-weight peptides (46,47),... 

Phosphotungstic acid Discriminating protein precipitant. Precipitates Milesi et al. (2007), Wilkinson et al. (1992),... 

Phosphotungstic acid finds use in the precipitation of proteins, alkaloids, and certain amino acids. The solubility of sodium phosphotungstate, contrasted with the comparative insolubility of the potassium and ammonium salts, has suggested its use as a reagent in qualitative analysis. 

Phosphoric acid white precipitate of phosphotungstic acid, H3[P04 (Wl2036)].5H20, soluble in excess of the reagent. 

In addition to concerns over the incomplete solubility of some of the H-coal vacuum-still bottom materials in toluene, the precipitation experiments just discussed are subject to problems associated with two-phase reactions in general. Incomplete contact between the organic compounds in toluene solution and the aqueous acids can lead to inconsistent precipitation results. With this in mind, a different approach was developed in which various H-coal vacuum-still bottoms were treated with phosphotungstic acid, which is soluble in tetrahydrofuran. This reagent allows precipitation to be accomplished from an initially one-phase system, and gives rise to crisp, easily collected salts. 

Table IV. Precipitation of Coal-Derived Bases with Phosphotungstic Acid...

Phosphotungstic acid and magnesium were used as precipitant. CHOD-PAP method for the determination of HDL-cholesterol. 

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