Dust cobalt

Gilman JPW, Ruckerbauer GM. 1962. Metal carcinogenesis I Observations on the carcinogenicity of a refinery dust, cobalt oxide and colloidal thorium dioxide. Cancer Res 22 152-156. 

SYNONYMS Cobalt oxide, cobalt chloride, aquacat, cobalt metal, fume and dust, cobalt carbonyl, cobalt hydrocarbonyl, synonyms vary by compound. 

SYNONYMS aquacat, cobalt metal dust, cobalt metal fume, super cobalt. 

Synonyms/Trade Names Cobalt metal dust, Cobalt metal fume... 

Exposure to cobalt (metal fumes and dust) should be limited to 0.05 mg/ms (8-hour time-weighted average 40-hour week). 

The ACGIH adopted TLV/TWA for 1992—1993 for fluorides as F is TWA 2.5 mg/m, and for cobalt as Co metal dust TWA 0.05 mg/m. Dust masks should be used while handling both the cobalt fluorides and all other cobalt compounds. CoF is shipped as an oxidizer and a corrosive material. 

Occupational exposure to dust of cemented carbide that contains more than 2% cobalt must be controlled so that employees are not exposed at a concentration greater than 0.1 mg cobalt/m air, determined as a TWA concentration for up to a 10-h workshift in a 40-h workweek. 

Copper sulfate, in small amounts, activates the zinc dust by forming zinc—copper couples. Arsenic(III) and antimony(TTT) oxides are used to remove cobalt and nickel they activate the zinc and form intermetaUic compounds such as CoAs (49). Antimony is less toxic than arsenic and its hydride, stibine, is less stable than arsine and does not form as readily. Hydrogen, formed in the purification tanks, may give these hydrides and venting and surveillance is mandatory. The reverse antimony procedure gives a good separation of cadmium and cobalt. 

Inhalation of extremely fine carbide, cobalt, and nickel powders should be avoided. Efficient exhaust devices, dust filters, and protective masks are essential when handling these powders. 

Coal tar pitch volatiles, see Particulate polycyclic aromatic hydrocarbons (PPAH), as benzene solubles Cobalt metal, dust and fume (as Co)... 

The finely powdered Raney cobalt alloy is a significant dust explosion hazard. 

The metallic couples of zinc vith copper, nickel or cobalt form readily by sonication of zinc dust with salts, mainly halides, of the second metal in aqueous organic solvents. This method avoids the usual tedious preparative methods [76-78]. 

The dust and powder of cobalt metal, ores, and some compounds, such as cobaltous nitrate [ColNOfljT bH O], are flammable and toxic if inhaled. Cobaltous acetate [ColCjHjOjlj dHjO], which is soluble in water, is not allowed to be used in food products because of its toxicity. 

Toxicology. Cobalt causes skin irritation, allergic contact dermatitis, and occupational asthma interstitial pulmonary fibrosis is associated with exposure to hard metal dust (tungsten and cobalt). 

Occupational exposure to cobalt dust has been associated with cardiomyopathy characterized by functional effects on the ventricles and enlargement of the heart. ... 

In finely powdered form, cobalt ignites spontaneously in air. Reactions with acetylene and bromine pentafluoride proceed to incandescence and can become violent. The metal is moderately toxic by ingestion. Inhalation of dusts can damage lungs. Skin contact with powdered material can cause dermatitis. 

Interestingly, low-valent cobalt species obtained by the in situ reduction of CoBrz with zinc catalyze the reaction of aryl bromides with zinc dust. The reaction allows the preparation of a range of functionalized arylzinc halides such as 44 (Scheme 19)". ... 

S203 Cobalt metal fume dust 0.1 MCEF Aqua regia AA 0. 031-0.22 (f)... 

Toxicity. Coball, like most oilier metals, is not entirely harmless, although ii is not in any way comparable lo the known toxic metals, such as mercury, cadmium, and lead. Inhalation of fine cobalt dust over long periods can cause an irritation of Ihe respiratory organs, which may result in chronic bronchitis. Complete recovery is usually achieved upon removal from the contaminated atmosphere. Cobalt salts can cause benign dermatoses, either in people new to handling them, or aflci prolonged exposure, usually several years. 

The neutral solution is purified to remove impurities more noble than zinc, e g., cadmium, copper, cobalt, nickel, arsenic, antimony, and germanium. The purification is accomplished by cementation in two or more steps with the addition of zinc dust. Generally, at least one cementation step is conducted at high temperature with arsenic, antimony, or copper-arsenic added. Cadmium is usually recovered in the metallic state and copper, nickel, and cobalt are recovered as sludges if present in sufficient quantities. 

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