Chromium , insoluble compounds

Cr(02CCH3)2]2,2H20. Red insoluble compound formed from sodium ethanoate and CrC)2 in aqueous solution. The most stable Cr(II) compound contains a Cr —Cr bond, chromium fluorides... 

Lake or pigment dyes form insoluble compounds with aluminum, barium, or chromium on molybdenum salts the precipitates are ground to form pigments used in paint and inks. 

Beryllium and beryllium compounds Insoluble chromium (VI) compounds Mustard gas (B,B -Dichlorodiethyl sulphide)... 

Induced dissolution is also a well known phenomenon and frequently applied in chemical analysis. To dissolve platinum easily it was suggested by Ropp that the sample should be alloyed with silver or copper, the alloys being easily soluble even in dilute acids. Anhydrous chromic chloride, insoluble in water and dilute acids, becomes easily soluble by adding metallic magnesium or zinc to the dilute acid . In this case the chromium(III) compound is reduced to chro-mium(II), which will be oxidized by the solvent to water-soluble chromium(III)... 

Only chromium (III) co-precipitates quantitatively with hydrated iron (III) oxide at the pH of seawater, around 8. In order to collect chromium (VI) directly without pre-treatment, e.g., reduction to chromium (III), hydrated bismuth oxide, which forms an insoluble compound with chromium (VI) was used. Chromium (III) is collected with hydrated bismuth oxide (50 mg per 400 ml seawater). Chromium (VI) in seawater is collected at about pH 4 and chromium (VI) is collected below pH 10. Thus both chromium (III) and chromium (VI) are collected quantitatively at the pH of seawater, i.e., around 8. 

Chromates. Epidemiological studies from around the world have consistently shown excess risks for lung cancer in workers involved in chromate and chromate pigment production. The epidemiological studies do not clearly implicate specific compounds but do implicate chromium(VT) compounds." (A recent report also implicated insoluble chromium(HI) as a cause of lung cancer in... 

Cadmium sulfide, chromium(lll) hydroxide, aluminum hydroxide, and nickel(ll) hydroxide are insoluble compounds in water. 

OSHA regulates chromium levels in the workplace air. The occupational exposure limits for an 8-hour workday, 40-hour workweek are 500 pg chromium/m3 for water-soluble chromic (chromium(HI)) or chromous [chromium(II)] salts and 1,000 pg chromium/m3 for metallic chromium (chromium(O)), and insoluble salts. The level of chromium trioxide (chromic acid) and other chromium(VI) compounds in the workplace air should not be higher than 52 pg chromium(VI)/m3 for any period of time. 

Trivalent chromium compounds, except for acetate, nitrate, and chromium(III) chloride-hexahydrate salts, are generally insoluble in water. Some hexavalent compounds, such as chromium trioxide (or chromic acid) and the ammonium and alkali metal (e.g., sodium, potassium) salts of chromic acid are readily soluble in water. The alkaline metal (e.g., calcium, strontium) salts of chromic acid are less soluble in water. The zinc and lead salts of chromic acid are practically insoluble in cold water. Chromium(VI) compounds are reduced to chromium(III) in the presence of oxidizable organic matter. However, in natural waters where there is a low concentration of reducing materials, chromium(VI) compounds are more stable (EPA 1984a). For more information on the physical and chemical properties of chromium, see Chapter 3. 

Cardiovascular Effects. Information regarding cardiovascular effects in humans after inhalation exposure to chromium and its compounds is limited. In a survey of a facility engaged in chromate production in Italy, where exposure concentrations were 0.01 mg chromium(VI)/m3, electrocardiograms were recorded for 22 of the 65 workers who worked in the production of dichromate and chromium trioxide for at least 1 year. No abnormalities were found (Sassi 1956). An extensive survey to determine the health status of chromate workers in seven U.S. chromate production plants found no association between heart disease or effects on blood pressure and exposure to chromates. Various manufacturing processes in the plants resulted in exposure of workers to chromite ore (mean time-weighted concentration of 0-0.89 mg chromium(ni)/m3) water-soluble chromium(VI) compounds (0.005-0.17 mg chromium(VI)/m3) and acid-soluble/water-insoluble chromium compounds (including basic chromium sulfate), which may or may not entirely represent trivalent chromium (0-0.47 mg chromium/m3) (PHS 1953). No excess deaths were observed from cardiovascular diseases and ischemic heart disease in a cohort of 4,227 stainless steel production workers from 1968 to 1984 when compared to expected deaths based on national rates and matched for age, sex, and calender time (Moulin et al. 1993). No measurements of exposure were provided. In a cohort of 3,408 individuals who had worked in 4 facilities that produced chromium compounds from chromite ore in northern New Jersey sometime between 1937 and 1971, where the exposure durations of workers ranged from <1 to >20 years, and no increases in atherosclerotic heart disease were evident (Rosenman and Stanbury 1996). The proportionate mortality ratios for white and black men were 97 (confidence limits 88-107) and 90 (confidence limits 72-111), respectively. 

Examination of end-of-shift chromium levels indicated a correlation between urinary chromium levels and exposure to soluble chromium(VI) compounds, but not to insoluble chromates or chromium(III) compounds (Minoia and Cavalleri 1988 Mutti et al. 1985b). The relationship between workroom air concentrations of water soluble chromium(VI) compounds and daily increases in urinary chromium (preexposure values subtracted from end-of-shift values) are shown in Figure 2-6. An increase in urinary chromium of 12.2 pg/g creatinine above pre-exposure values or a total concentration of 29.8 pg/g creatinine (end-of-shift values) corresponded to an air concentration of 50 pg chromium(VI)/m3 from welding fumes (Mutti et al. 1985b). 

ACGIH TLV-TWA—Chromium, metal and inorganic compounds as Cr Metal and chromium(lll) compounds Water soluble chromium(VI) compounds Insoluble chromium(VI) compounds 0.5 mg/m3 0.05 mg/m3 0.01 mg/m3 ACGIH 1999... 

FeS.Cr2S3 results 4 on heating a mixture of iron, chromium hydroxide, and sulphur, as a black insoluble compound. 

Large amounts of sodium dichromate, Na,Cto07 2Ho0, are used in the tanning of hides, to produce chrome-tanned leather. The chromium forms an insoluble compound with the leather protein. 

Inorganic Salt Preservatives. Inorganic compounds used to formulate wood preservatives are normally water soluble. As a result, the salts deposited in the wood are susceptible to leaching unless they are transformed to insoluble compounds or are chemically fixed to the wood substrate. Indeed, such conversions do occur as a result of interactions between some of the salts and the wood substrate. Both single element and multicomponent reactions are involved in the fixation mechanisms copper and chromium are the most reactive of the possible components. 

Levis AG, Majone F. 1981. Cytotoxic and clastogenic effects of soluble and insoluble compounds containing hexavalent and trivalent chromium. Br J Cancer 44 219-235. 

The OSHA PEL is 0.005 mg CrOs/m (8-hour TWA) for chromic acid and chromates (ineluding tert-butyl ehromate with a skin designation and zinc chromate) 0.5 mg Cr/m (8-hour TWA) for chromium(II) and chromium(III) compounds and 1 mg Cr/m (8-hour TWA) for chromium metal and insoluble salts. 

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