Of chromium compounds

Special pink or mby variations of the white abrasive are produced by adding small amounts of chromium compounds to the melt. The color is dependent on the amount of chromium added. A green alumina, developed by Simonds Abrasives, results from small additions of vanadia [11099-11-9]. Each was developed to improve on the suitabiUty of white abrasive for tool and precision grinding. 

Preparation and chemistry of chromium compounds can be found ia several standard reference books and advanced texts (7,11,12,14). Standard reduction potentials for select chromium species are given ia Table 2 whereas Table 3 is a summary of hydrolysis, complex formation, or other equilibrium constants for oxidation states II, III, and VI. 

Acute and Chronic Toxicity. Although chromium displays nine oxidation states, the low oxidation state compounds, -II to I, all require Special conditions for existence and have very short lifetimes in a normal environment. This is also tme for most organ ochromium compounds, ie, compounds containing Cr—C bonds. Chromium compounds that exhibit stabiUty under the usual ambient conditions are limited to oxidation states II, III, IV, V, and VI. Only Cr(III) and Cr(VI) compounds are produced in large quantities and are accessible to most of the population. Therefore, the toxicology of chromium compounds has been historically limited to these two states, and virtually all of the available information is about compounds of Cr(III) and/or Cr(VI) (59,104). However, there is some indication that Cr(V) may play a role in chromium toxicity (59,105—107). Reference 104 provides an overview and summary of the environmental, biological, and medical effects of chromium and chromium compounds as of the late 1980s. 

Workplace. The Occupational Safety and Health Administration (OHSA) has estabUshed workplace permissible exposure limits (PEL) for chromium metal and three forms of chromium compounds. OSHA s PEL for chromic acid and chromates is 0.1 mg/m 3 both a ceiling, ie, no exposure above this concentration is allowed, and an 8-h time-weighted average (TWA). Chromium metal and insoluble chromium salts have an 8-h TWA PEL of 1.0 mg/m Cr, and the same standard is 0.5 mg/m Cr for soluble Cr(III) and Cr(II) compounds (144). 

Another use of chromium compounds is ia the production of water- and oil-resistant coatings on textiles, plastic, and fiber glass. Trade names are Quilon, Volan, and Scotchgard (197,198) (see Waterproofing and water/oilrepellancy). 

Wood Preservation. The use of chromium compounds ia wood preservation is largely because of the excellent results achieved by chromated copper arsenate (CCA), available ia three modifications under a variety of trade names. The treated wood (qv) is free from bleeding, has an attractive ohve-green color, and is paintable. CCA is widely used, especially ia treating utility poles, bull ding lumber, and wood foundations. About 62% of all the chromic acid produced ia the United States is consumed by the wood preservation industry (77,167) (see Building materials, survey). 

Miscellaneous Uses. A large number of chromium compounds have been sold in small quantities for a variety of uses, some of which ate described in Table 14 (1,236—238). 

Ca.ta.lysts, A more important minor use of chromium compounds is ia the manufacture of catalysts (Table 14). Chromium catalysts are used ia a great variety of reactions, including hydrogenations, oxidations, and polymerizations (229—231). Most of the details are proprietary and many patents are available. 

Catalytic elfects on the thermal decomposition and burning under nitrogen of the nitrate were determined for ammonium dichromate, potassium dichromate, potassium chromate, barium chloride, sodium chloride and potassium nitrate. Chromium(VI) salts are most effective in decomposition, and the halides salts during burning of the nitrate [1]. The effect of chromium compounds soluble in the molten nitrate, all of which promote decomposition of the latter, was studied (especially using ammonium dichromate) in kinetic experiments [2],... 

Bioavailability of chromium compounds from environmental media... 

Nieboer, E. and S.L. Shaw. 1988. Mutagenic and other genotoxic effects of chromium compounds. Pages 399 441 in J.O. Nriagu and E. Nieboer (eds.). Chromium in the Natural and Human Environments. John Wiley, NY. 

Chromium(III) hydroxide, like aluminium hydroxide, possesses adsorptive power, and the use of chromium compounds as mordants is due to this property. 

Polymers of chromium compounds of this type are also known. Thus, [Cr(NH3)3(SCN)3], which has been prepared up to pentamolecular form. 

The chemistry shown in Scheme 1 represents a novel route to Cr(V) complexes. Such a mechanism may be important in biological environments and potentially involved in complex processes responsible for carcinogenicity of chromium compounds (112). 

The spectra of chromium compounds (H20)5CrIII-CR1R2R3 were studied intensively and the following conclusion were derived (104). 

Li st of Chromium Compounds Chromium AcetylacetonateorChromylacetyl-acetone. See Vol 1, pA53-R Addnl Ref F.Bellinger et al, IEC 40, 1330 (1948) CA42, 6115 (1948) [it was found that Cr acetyl ace ton ate added in quantities of about 2% (together with 4% of gasoline) to nitromethane, prevented its detonation when used a rocket proplnt such as for launching a buzz bomb]... 

A great effort is dedicated to the development of methodologies for the oxidation of alcohols, involving catalytic quantities of chromium compounds, which are re-oxidized with other oxidants present in excess.406 Using chromium compounds in catalytic amounts is environmentally sound, and often facilitates the work-ups. 

Bray, D.J., Toxicity of chromium compounds formed in refractories , Bull. Amer. Ceram. Soc., 1985 64(7) 1012-16. 

Chromium (IV) Production of chromium compounds, paint pigments, reduction of chromite ore Lung cancer... 

Hepatic Effects. Chromium(VI) has been reported to cause severe liver effects in four of five workers exposed to chromium trioxide in the chrome plating industry. Derangement of the cells in the liver, necrosis, lymphocytic and histiocytic infiltration, and increases in Kupffer cells were reported. Abnormalities in tests for hepatic dysfunction included increases in sulfobromophthalein retention, gamma globulin, icterus, cephalin cholesterol flocculation, and thymol turbidity (Pascale et al. 1952). In a cohort of 4,227 workers involved in production of stainless steel from 1968 to 1984, excess deaths were observed from cirrhosis of the liver compared to expected deaths (0/E=55/31.6) based on national rates and matched for age, sex, and calender time having an SMR of 174 with confidence limits of 131-226 (Moulin et al. 1993). No measurements of exposure were provided. Based on limited information, however, the production of chromium compounds does not appear to be associated with liver effects. As part of a mortality and morbidity study of workers engaged in the manufacture of chromium(VI) compounds (84%) and chromium(III) compounds (16%) derived from chromium(VI) in Japan, 94 workers who had been exposed for 1-28 years were given a complete series of liver function... 

Studies of chromate production workers, who are exposed to a variety of chromium compounds both hexavalent and trivalent, and chromate pigment industries, where exposure is mainly to chromium(VI), have consistently demonstrated an association with respiratory system cancer. Studies in chrome platers, who are exposed to chromium(VI) and other agents, including nickel, generally support the conclusion that certain chromium(VI) compounds are carcinogenic. Studies in stainless steel welders exposed to chromium(VI) and other chemicals, and in ferrochromium alloy workers, who are exposed mainly to chromium(O) and chromium(III), but also to some chromium(VI), were inconclusive. Studies in leather tanners, who are exposed to chromium(III), were consistently negative. 

Ingestion of chromium compounds as a result of exposure at the workplace has occasionally produced gastrointestinal effects. In a chrome plating plant where poor exhaust resulted in excessively high... 

Dermal Effects. Occupational exposure to airborne chromium compounds has been associated with effects on the nasal septum, such as ulceration and perforation. These studies are discussed in Section 2.2.1.2 on Respiratory Effects. Dermal exposure to chromium compounds can cause contact allergic dermatitis in sensitive individuals, which is discussed in Section 2.2.3.3. Skin burns, blisters, and skin ulcers, also known as chrome holes or chrome sores, are more likely associated with direct dermal contact with solutions of chromium compounds, but exposure of the skin to airborne fumes and mists of chromium compounds may contribute to these effects. 

Direct contact of the eyes with chromium compounds also causes ocular effects. Corneal vesication was described in a worker who accidentally got a crystal of potassium dichromate or a drop of a potassium dichromate solution in his eye (Thomson 1903). In an extensive study of chromate workers in seven U.S. chromate production plants, eyes were examined because accidental splashes of chromium compounds into the eye had been observed in these plants. Congestion of the conjunctiva was found in 38.7% of the 897 workers, discharge in 3.2%, corneal scaring in 2.3%, any abnormal finding in 40.8%, and burning in 17.0%, compared with respective frequencies of 25.8,1.3, 2.6, 29.0, and 22.6% in 155 nonchromate... 

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