Chromium-containing compounds

States are potentially exposed to chromium and chromium-containing compounds in the workplace. 

Industrial facilities that manufacture or use chromium and chromium-containing compounds... 

Newbold RF, Amos J, Connell JR. 1979. The cytotoxic, mutagenic and clastogenic effects of chromium-containing compounds on mammalian cells in culture. Mutat Res 67 55-63. 

In all the precipitates only a hydrotalcite-1ike phase was present, with lower crystal size for the chromium containing compounds. After calcination, a strong increase of the surface area was observed for all the samples. They also showed pore size distribution curves with a narrow peak centered around the most frequently occurring pore radius (28) and low crystal sizes. 

Chromium-containing wood preservatives and their chemical compositions are Hsted ia Table 13 (199). Chromium compounds have a triple function ia wood preservation (200). Most importantiy, after impregnation of the wood the Cr(VI) compounds used ia the formulations react with the wood extractives and the other preservative salts to produce relatively insoluble complexes from which preservative leaches only very slowly. This mechanism has been studied in the laboratory (201—206) and the field (207). Finally, although most of the chromium is reduced to chromium (ITT), there is probably some slight contribution of the chromium (VT) to the preservative value (208). 

In the cases of Cr03/Si02 and Cr(7r-C3H6)3/Si02 systems a considerable part of the chromium contained in the catalyst is involved in the propagation center formation. In these catalysts all the ions of the transition metals are on the surface and the active component seems to be the main type of compounds present on the catalyst surface. 

The ideal disposal method is a chemical treatment that can convert hazardous waste into environmentally benign materials. For example, trichloroethylene (CI2 C I CHCl) is highly toxic to aquatic life, but this compound can be made nontoxic by chemical treatment that converts its chlorine atoms into chloride anions. Similarly, the chromium-containing waste from electroplating operations contains highly toxic CrOq anions, but a chemical treatment that converts CrOq into Cr causes the chromium to precipitate from the solution as insoluble Cr (OH). This removal of chromium detoxifies the water. 

The use of heterogeneous catalysts in the liquid phase offers several advantages compared with homogeneous counterparts, in that it facilitates ease of recovery and recycling. A chromium-containing medium-pore molecular sieve (Si Cr > 140 1), CrS-2, efficiently catalyzes the direct oxidation of various primary amines to the corresponding nitro compounds using 70% t-butylhydroperoxide (TBHP).110... 

Catalysts suitable specifically for reduction of carbon-oxygen bonds are based on oxides of copper, zinc and chromium Adkins catalysts). The so-called copper chromite (which is not necessarily a stoichiometric compound) is prepared by thermal decomposition of ammonium chromate and copper nitrate [50]. Its activity and stability is improved if barium nitrate is added before the thermal decomposition [57]. Similarly prepared zinc chromite is suitable for reductions of unsaturated acids and esters to unsaturated alcohols [52]. These catalysts are used specifically for reduction of carbonyl- and carboxyl-containing compounds to alcohols. Aldehydes and ketones are reduced at 150-200° and 100-150 atm, whereas esters and acids require temperatures up to 300° and pressures up to 350 atm. Because such conditions require special equipment and because all reductions achievable with copper chromite catalysts can be accomplished by hydrides and complex hydrides the use of Adkins catalyst in the laboratory is very limited. 

The more cationic halogen containing compounds produced other products. Cobalt bis-allyliodide produced cis-polybutadiene and the even more cationic chromium, produced cyclododecatriene. Only with the more cationic system which introduced trans-structures, was cyclization and reduction of the metal able to intercept the polymerization reaction. Cyclization was not possible in the less cationic cobalt which produces all cis-polybutadiene nor was the hydride transfer possible with the less anionic chromium tris-allyl compound. 

Tricarbonyl(naphthalene)chromium, 19 Tungsten carbonyl, 49 Metal-containing compounds Aluminum Compounds Alkylaluminum halides, 5, 25, 44, 173, 306... 

Metal-containing compounds, Chromium Compounds (Continued) Chromium(VI) oxide-Chlorotrimethyl-silane, 327... 

It has been suggested that GTF is not a chromium complex.1091 This arises from the failure to isolate a biologically active Crm complex from extracts of brewers yeast grown in a medium containing added Crm. Two fractions showed biological activity, but further purification resulted in the loss of chromium and the isolation of biologically active chromium-free compounds. One of these was largely tyramine (formed from tyrosine residues), but pure tyramine does not show GTF-type properties. The activity of this fraction must therefore be due to the minor component... 

---