Tungsten soluble compounds

Tungsten (soluble compounds, as W) Formula CAS RTECS IDLH N.Q... 

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. 

Triphenyl phosphate Tungsten and compounds (as W) soluble insoluble F (0.8 pm MCEF)... 

Toxicology. The soluble compounds of tungsten are distinctly more toxic than the insoluble forms. 

The 2003 ACGIH threshold limit valuetime-weighted average (TLV-TWA) for tungsten is 1 mg/m , as W for soluble compounds, with a short-term excursion limit (STEL) of 3 mg/m , and 5 mg/m as W for insoluble compounds with a STEL of lOmg/mh... 

Tungsten and compounds Few reports of human toxicity. Some saits may reiease aoid upon contaot with moisture. Chronic exposure to tungsten carbide cobait amaigams in the hard-metais industry may be associated with fibrotic iung disease. See cobait. 5 mg/m (insoluble compounds) 1 mg/m (soluble compounds) Elemental tungsten is a gray, hard, brittle metal. Finely divided powders are flammable. 

As seven-coordinate tungsten(II) compounds containing phosphine ligands have been shown by Bencze [29-32] and others [33, 37] to be efficient catalysts in a number of important catalytic reactions, we have turned our attention towards the synthesis of more soluble and versatile derivatives containing nitrile ligands [38, 39]. Nitrile ligands are more labile than phosphine and may result in enhanced activity. 

In the United States, occupational exposure limits have been assigned to 5 mg W/m for insoluble tungsten compounds and to 1 mg W/m for soluble compounds. 

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

In 1826 J. J. Berzelius found that acidification of solutions containing both molybdate and phosphate produced a yellow crystalline precipitate. This was the first example of a heteropolyanion and it actually contains the phos-phomolybdate ion, [PMoi204o] , which can be used in the quantitative estimation of phosphate. Since its discovery a host of other heteropolyanions have been prepared, mostly with molybdenum and tungsten but with more than 50 different heteroatoms, which include many non-metals and most transition metals — often in more than one oxidation state. Unless the heteroatom contributes to the colour, the heteropoly-molybdates and -tungstates are generally of varying shades of yellow. The free acids and the salts of small cations are extremely soluble in water but the salts of large cations such as Cs, Ba" and Pb" are usually insoluble. The solid salts are noticeably more stable thermally than are the salts of isopolyanions. Heteropoly compounds have been applied extensively as catalysts in the petrochemicals industry, as precipitants for numerous dyes with which they form lakes and, in the case of the Mo compounds, as flame retardants. 

Bis(3,5-dimethylpyrazol-l-yl)cyclotriphosphazene containing phenyl substituents at the phosphorus atoms (R) reacts with molybdenum and tungsten hexacar-bonylstogive34(R = Ph M = Mo, W) [94JCS(D)63]. IfRj = N(Me)(CH2)20, compounds 34 (R2 = N(Me)(CH2)20 M = Mo, W) having better solubility in organic solvents are produced. Their structures show the novel tridentate NNN feature of the ligands. 

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