Chemical Fact Sheet
Cobalt
| Chemical Abstract Number (CAS #) | 7440-48-4 |
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| Synonyms | CI-77320; KOBALT- (GERMAN,POLISH); NCI-C60311 |
| Analytical Methods | 200.7 - 200.8 - 6010 - 6020 |
| Molecular Formula | Co |
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Synopsis
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Cobalt - (Kobald, from the German, goblin or evil spirit, cobalos, Greek, mine), Co; at. wt. 58.93320(l); at. no. 27; m.p. 1495 deg C; b.p. 2927 deg C; sp. gr. 8.9 (20 deg C); valence 2 or 3. Discovered by Brandt about 1735. Cobalt occurs in the mineral cobaltite, smaltite, and erythrite, and is often associated with nickel, silver, lead, copper, and iron ores, from which it is most frequently obtained as a by-product. It is also present in meteorites. Important ore deposits are found in Zaire, Morocco, and Canada. The U.S. Geological Survey has announced that the bottom of the north central Pacific Ocean may have cobalt-rich deposits at relatively shallow depths in waters close to the Hawaiian Islands and other U.S. Pacific territories. Cobalt is a brittle, hard metal, closely resembling iron and nickel in appearance. It has a magnetic permeability of about two thirds that of iron. Cobalt tends to exist as a mixture of two allotropes over a wide temperature range; the beta-form predominates below 400 deg C, and the alpha above that temperature. The transformation is sluggish and accounts in part for the wide variation in reported data on physical properties of cobalt. It is alloyed with iron, nickel and other metals to make Alnico, an alloy of unusual magnetic strength with many important uses. Stellite alloys, containing cobalt, chromium, and tungsten, are used for high-speed, heavy-duty, high temperature cutting tools, and for dies. Cobalt is also used in other magnet steels and stainless steels, and in alloys used in jet turbines and gas turbine generators. The metal is used in electroplating because of its appearance, hardness, and resistance to oxidation. The salts have been used for centuries for the production of brilliant and permanent blue colors in porcelain, glass, pottery, tiles, and enamels. It is the principal ingredient in Sevre's and Thenard's blue. A solution of the chloride (CoCl2 - 6H2O) is used as sympathetic ink. The cobalt ammines are of interest; the oxide and the nitrate are important. Cobalt carefully used in the form of the chloride, sulfate, acetate, or nitrate has been found effective in correcting a certain mineral deficiency disease in animals. Soils should contain 0.13 to 0.30 ppm of cobalt for proper animal nutrition. Cobalt is found in Vitamin B-12, which is essential for human nutrition. Cobalt-60, an artificial isotope, is an important gamma ray source, and is extensively used as a tracer and a radiotherapeutic agent. Single compact sources of Cobalt-60 vary from about $1 to $10/curie, depending on quantity and specific activity. Twenty six isotopes and isomers of cobalt are known. |
| Use | MFR COBALT SALTS, IN NUCLEAR TECHNOLOGY. /(60)COBALT/ MFR OF PERMANENT MAGNETS; IN TOOLS, CARS, ELECTRICAL & AIRCRAFT INDUSTRY PRODUCTION OF COBALT BEARING ALLOYS, CUTTING MATERIALS, WEAR-RESISTANT MATERIALS, LACQUERS, VARNISHES, PAINT DRIERS; PRODUCTION OF INKS, ENAMELS, FRITS, GLAZES, GLASS DECOLORIZER, CATALYSTS (60)COBALT FOR EXPTL WATER TREATMENT. Synthesis of heating fuels; catalyst in hydrocarbon refining In alloys as dental materials Cobalt bearing materials incorporated in the frit composition enhance the adherence of the enamel to sheet steel. Cobalt molybdenum alloys are used for the desulfurization of high-sulfur bituminous coal, and cobalt iron alloys in the hydrocracking of crude oil shale and in coal liquefaction. As cobalamin tracer /(57)Cobalt/ Medication: Used in gamma ray therapy of carcinoma /(60)Cobalt/ Used for sterilization and perservation purposes /(60)Cobalt/ PREPN OF HIGH PURITY METAL: WARE IN ULTRAPURIFICATION OF SEMICONDUCTOR MATERIALS, MS BROOKS, JK KENNEDY, EDS (MACMILLAN, NY, 1962) PP 192-204. REACTOR-PRODUCED (60)COBALT ... IS WIDELY USED SOURCE OF RADIOACTIVITY. /(60)COBALT/ (60)COBALT IN EXPTL MEDICINE & CANCER RESEARCH. /(60)COBALT/ THE ONLY DISEASES IN WHICH THE CLINICAL USE OF COBALT IS STILL ADVOCATED BY SOME IS THE NORMOCHROMIC, NORMOCYTIC ANEMIA ASSOC WITH SEVERE RENAL FAILURE. |
| Consumption Patterns | In 1982, about three quarters of the USA consumption of cobalt was in the production of steel and alloys, esp in so called superalloys used in jet engines and in magnetic materials used for various electronic applications. The remaining quarter went to different types of salts and driers. Superalloys, mainly for industrial and aircraft gas turbine engines, 37%; Magnetic materials, 17%; Driers, 10%; Catalysts, 10%; Metal cutting and mining tool bits, 6%; and Other, 23% (1985) Superalloys used mainly in industrial and aircraft gas turbine engines accounted for about 38% of reported consumption; paint driers, 15%; magnetic alloys, 12%; catalysts, 9%; and other, 26%. Total estimated value of cobalt consumed in 1988 was $130 million. |
| Apparent Color | SILVERY GRAY METAL, CUBIC; SILVERY BLUISH-WHITE METAL |
| Odor | Odorless |
| Boiling Point | 2870 deg C |
| Melting Point | 1493 DEG C |
| Molecular Weight | 58.9332 |
| Density | 8.92 @ 20 DEG C |
| Sensitivity Data | Cobalt dust is mildly irritating to the eyes and to a lesser extent to the skin. |
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Chemical and Physical Properties |
MAGNETIC, DUCTILE, SOMEWHAT MALLEABLE METAL; BRINELL HARDNESS: 125; LATENT HEAT OF FUSION: 62 CAL/G SPECIFIC HEAT (15-100 DEG C)= 0.1056 CAL/G/DEG C; ATOMIC NUMBER 27; VERY SLOWLY ATTACKED BY HYDROCHLORIC ACID OR COLD SULFURIC ACID; VALENCES 1, 2, 3; RARELY 4, 5 HAS MAGNETIC PROPERTIES BUT PASSES @ 1115 DEG C INTO NON-MAGNETIC FORM ONE NATURALLY OCCURRING ISOTOPE: (59)COBALT; ARTIFICIAL ISOTOPES: 54-58; 60-64. /(59)COBALT/ TENDS TO EXIST AS MIXT OF TWO ALLOTROPES OVER WIDE TEMP RANGE; BETA FORM PREDOMINATES BELOW 400 DEG C; ALPHA ABOVE THAT TEMP Chill value of cobalt (100% pure): +1.40 Electrical conductivity: 27.6% IACS; Electrical resistivity: 6.2 u omega.cm; Thermal conductivity: 71.128 W/m.deg K; Tensile strength: 234-945 mPa at room temp Metallic cobalt dissolves readily in dilute sulfuric acid, hydrochloric acid, or nitric acid to form cobaltous salts. The presence of cobalt in iron alloys results in substantial incr in magnetic retentivity. Slowly attacked by ammonium hydroxide and sodium hydroxide. Half-life: 70.8 days /(58)Cobalt/ Half-life: 78.8 days /(56)Cobalt/ Half-life: 271 days /(57)Cobalt/ Half-life: 5.27 days /(60)Cobalt/ In its cmpd cobalt occurs normally in the oxidation states +2 and +3 more seldom in the oxidation states 0, +1, and +4. In normal salts the bivalent form is more stable than the trivalent one, the reverse is true for cobalt complexes. |
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Environmental Impact |
IT HAS BEEN POINTED OUT THAT COBALT WAS INVARIABLY PRESENT IN ATMOSPHERE EVEN IN PLACES WHERE NO MANUFACTURING OPERATIONS WERE IN QUESTION, AND THAT ALL INDIVIDUALS EMPLOYED IN PLANTS BREATHED IN SOME COBALT EVEN IF IN MINUTE AMT.COBALT ALLERGY IS SEEN IN MANY OCCUPATIONS INCL BUILDING & CIVIL ENGINEERING METALWORK, PRINTING, AND POTTERY, LEATHER AND TEXTILE INDUSTRIES; COBALT MAY SOMETIMES BE THE CAUSATIVE AGENT IN CEMENT ECZEMA. SURVEY MADE BY THE PENNSYLVANIA DEPT OF HEALTH SHOWED BREATHING ZONE CONCN COULD BE CONTROLLED TO ABOUT 0.07 MG/CU M; WITHOUT CONTROL, CONCN WERE ABOUT 0.5 MG/CU M. Occupations with potential exposure to cobalt: acetic acid makers; alloy makers; alnico magnet makers; ammonia mask makers; barometer makers; bright platers; catalyst workers; cement makers; cemented carbide workers; ceramic workers; cement makers; cobalt soap makers; cosmetic makers; dye workers; drug makers; electroplaters; enamelers; ethyl acrylate makers; fertilizer workers; frit workers; gas mask makers; gasoline blenders; glass colorers; glaze workers; high-speed tool steel workers; hygrometer makers; ink makers; iron-cobalt platers; lamp filament makers; magnet steel workers; metal smelterers; nickel by-product workers; paint drier makers; painters; porcelain workers; protective-coating makers; refractory brick makers; rubber makers; silicate paint makers; stone preserver makers; weatherproof cement makers; welders.A tungsten carbide facility reported that during 1977-78 the concn of cobalt in worker breathing zones average 0.048 mg/cu m in the powder area, 0.33 mg/cu m in the pressing area, 0.019 mg/cu m in grinding, and 0.25 mg/cu m for general maintenance. The highest concn measured was 0.17 mg/cu m and the lowest was 0.004 mg/cu m. More than a million workers in the USA are potentially exposed to cobalt or its cmpd, many of them, however, to a limited degree, eg, when using cobalt-containing paint driers. Heavier exposure may result from mining processes, in the production of cobalt powder and alloys and in the cemented tungsten carbide industry. Liberation during grinding and sharpening of cemented carbide and steel tools; during synthesis of cobalt cmpd for use as catalysts and driers; during refining and concn of ores. Liberation during manufacture of metal items from cutting tool and tool steels; during manufacture of metal items from hard facing alloys; during manufacture of items containing low-expansion alloys; during manufacture of metal items containing constant-modulus alloys; metal to glass seals in electric lamps, vacuum tubes, and x-ray tubes. Liberation during manufacture of dental prosthetic and osteosynthetic items; during asbestos fiber processing. |
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Environmental Fate |
Widely distributed in nature; abundance in earth's crust 0.001-0.002%. Principal ores include linnaeite (Co3S4). IN MINERALS COBALTITE, SMALTITE, & ERYTHRITE & IS OFTEN ASSOCIATED WITH NICKEL, SILVER, LEAD, COPPER, & IRON ORES FROM WHICH IT IS OBTAINED AS BY-PRODUCT. ALSO PRESENT IN METEORITES. IMPORTANT ORE DEPOSITS ARE FOUND IN ZAIRE, MOROCCO, & CANADA. Cobalt is a by product or coproduct of the refining of other mined metals such as copper and nickel. Some of the commercially mined ores are carrollite, smaltite, cobaltite, siegenite, and sphaerocobaltite. The amount of cobalt mined is relatively small in comparison with copper, nickel, and the cobalt supply depends to a large extent on the demand for the latter two metals. Metal content of Igneous Rocks, Ore Deposits and Concentrates, wt%: Cobalt: Igneous rocks 0.001 & Ore deposits 1-11 IN MINERALS COBALTITE, SMALTITE,ERYTHRITE,IS OFTEN ASSOCIATED WITH NICKEL, SILVER, LEAD, COPPER, and IRON ORES. MAJOR SOURCE OF COBALT IS FOOD; CONCN IN GREEN, LEAFY VEGETABLES MAY BE AS GREAT AS 0.5 MG/KG DRY WT. BIOC: Only a few plant species accumulate cobalt above the 100 ppm which causes severe phytotoxicity. Hyperaccumulators of cobalt have been found which contain over 1% cobalt in dry leaves. Soil pH is very important in cobalt uptake and phyto-toxicity. More acidic soils sorb cobalt less strongly .Oats and barley grown in an acid sulfate soil area on the coast of the Gulf of Bothnia have exhibited exceptionally high concentrations of cobalt, nickel, and manganese. The objective of this study was to identify the factors contributing to this phenomenon by examinging 63 samples from acid sulfate soils and 35 samples from other soils of the area. The samples, taken from the plough layer, were attracted for determination of cobalt, nickel, and manganese with aqua regia (total) or 0.5 M ammonium acetate-0.5 M acetic acid-0.02 M sodium-EDTA, pH 4.65; manganese was also extracted with 1 M potassium chloride. The two soil groups did not differ in terms of total cobalt, nickel, or manganese but the amounts of ammonium acetate-0.5M acetic acid-0.02 M sodium-EDTA extractable cobalt and nickel, and potassium extractable manganese were two to three times greater in the acid sulfate soils than in the other soils. The amounts of cobalt and nickel extracted by both procedures were in close correlation with each other and with manganese. Total cobalt, nickel, and manganese content and soil pH explained 58-69% of the variation of ammonium acetate-0.5M acetic acid-0.02 M sodium-EDTA extractable cobalt and nickel as well as potassium chloride extractable manganese. IN PROCESS OF WEATHERING, COBALT MAY BE TAKEN INTO SOLN MORE READILY THAN NICKEL. IT IS ADSORBED TO GREAT EXTENT BY HYDROLYSATE OR OXIDATE SEDIMENTS. COBALT MAY BE TAKEN INTO SOLN IN SMALL AMT THROUGH BACTERIOLOGICAL ACTIVITY SIMILAR TO THAT CAUSING SOLN OF MANGANESE. The availability of cobalt is primarily regulated by pH and is usually found in soils as divalent cobalt. At low pH it is oxidized to trivalent cobalt and often found associated with iron. Adsorption of divalent cobalt on soil colloids is high between pH 6 and 7, whereas leaching and plant uptake of cobalt are enhanced by a lower pH |
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Disposal |
At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices. Cobalt metal may be recovered from scrap as alternatives to disposal. The following wastewater treatment technologies have been investigated for cobalt: Biological treatment chemical precipitation Reuse & landfill: Place material in sealed containers for reclamation or for disposal in an approved chemical landfill. Proper mixing of the cobalt waste and the soil is essential to preventing excessive plant accumulation of cobalt. |
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Atmosphere |
Cobalt concn in ambient air during use of hard metal: range: 0.180-0.193 mg/cu m; personal sampling. Cobalt concn in ambient air during grinding of hard metal: up to 61 ug/cu m; stationary sampling. Cobalt concn in ambient air during production of hard metal tools; mean values between 28-367 ug/cu m; personal sampling Cobalt concn in ambient air during production of hard metal; breathable dust range: 0.3-15 mg/cu m with 4-17% cobalt. Cobalt concn in ambient air during production of hard metal; range: approx 0.002-0.1 mg/cu m; median value: approx 0.01 mg/cu m; personal sampling Cobalt concn in ambient air during manufacturing of cobalt salts: medium: 0.2 mg/cu m; range: 0.1-3.0 mg/cu m; personal sampling. Cobalt concn in ambient air during production of cobalt salts: mean values between 49 and 1046 ug/cu m; stationary sampling. Reported concn in ambient air of several places in North and South America and in the United Kingdom range between 0.07 and 5 ng/cu m. Air samples collected near a Belgian cobalt manufacturing plant showed levels 0.4-7.3 ng/cu m. The atmospheric concn of cobalt in remote areas is very low, less than 1 ng/cu m in the antarctic. In other areas the ambient air concn is usually higher, in the order of 1 ng/cu m. Levels exceeding 10 ng/cu m have occasionally been reported in heavily industrialized cities. |
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