Cobalt compounds decompositions

Hofer et al. [671] observed that the decompositions of Ni3C and Co2C (the iron compounds melt) obeyed the zero-order equation for 0.3 < a < 0.9 (596-628 K and E = 255 kJ mole-1) and 0.2 < a < 0.75 (573-623 K and E = 227 kJ mole-1), respectively. The magnitudes of the rate coefficients for the two reactions were closely similar but the nickel compound exhibited a long induction period and an acceleratory process which was not characteristic of the reaction of the cobalt compound. Decomposition mechanisms were not discussed. 

The mauve colored cobalt(II) carbonate [7542-09-8] of commerce is a basic material of indeterminate stoichiometry, (CoCO ) ( (0 )2) H20, that contains 45—47% cobalt. It is prepared by adding a hot solution of cobalt salts to a hot sodium carbonate or sodium bicarbonate solution. Precipitation from cold solutions gives a light blue unstable product. Dissolution of cobalt metal in ammonium carbonate solution followed by thermal decomposition of the solution gives a relatively dense carbonate. Basic cobalt carbonate is virtually insoluble in water, but dissolves in acids and ammonia solutions. It is used in the preparation of pigments and as a starting material in the preparation of cobalt compounds. 

The breadth of reactions catalyzed by cobalt compounds is large. Some types of reactions are hydrotreating petroleum (qv), hydrogenation, dehydrogenation, hydrodenitrification, hydrodesulfurization, selective oxidations, ammonoxidations, complete oxidations, hydroformylations, polymerizations, selective decompositions, ammonia (qv) synthesis, and fluorocarbon synthesis (see Fluorine compounds, organic). 

Cobalt salts are used as activators for catalysts, fuel cells (qv), and batteries. Thermal decomposition of cobalt oxalate is used in the production of cobalt powder. Cobalt compounds have been used as selective absorbers for oxygen, in electrostatographic toners, as fluoridating agents, and in molecular sieves. Cobalt ethyUiexanoate and cobalt naphthenate are used as accelerators with methyl ethyl ketone peroxide for the room temperature cure of polyester resins. 

Definitive toxicity data for cobalt hydrocarbonyl do not exist because of the rapid decomposition in air of the chemical to a solid particulate. In most cases, exposures are primarily to inorganic cobalt compounds. 

The thermal stability of poly(vinyl chloride) is improved greatly by the in situ polymerization of butadiene or by reaction with preformed cis-1,4-polybutadiene using a diethyl-aluminum chloride-cobalt compound catalyst system. The improved thermal stability at 3-10% add-on is manifested by greatly reduced discoloration when the modified poly-(vinyl chloride) is compression molded at 200°C in air in the absence of a stabilizer, hydrogen chloride evolution at 180°C is retarded, and the temperature for the onset of HCl evolution and the peak decomposition temperature (DTA) increase, i.e. 260°-280°C and 290°-325° C, respectively, compared with 240°-260°C and 260°-280°C for the unmodified homopolymer, in the absence of stabilizer. The grafting reaction may be carried out on suspension, emulsion, or bulk polymerized poly(vinyl chloride) with little or no change in the glass transition temperature. 

Cobalt compounds are generally the more effective catalysts and consequently have received the most attention.34,112 131c Much information has been gained from studies of cobalt-catalyzed decompositions of alkyl hydroperoxides under nonautoxidizing conditions. One important point to be borne in mind in these studies is that radical-induced chain decomposition of the hydroperoxide, via reactions (55) and (56), is always in competition with decomposition via the foregoing cycle. 

Group 2B IMEMDT 52,363,91 Human Inadequate Evidence IMEMDT 52,363,91. SAFETY PROFILE Moderately toxic by ingestion. Questionable carcinogen. A skin and eye irritant. Human mutation data reported. See also COBALT COMPOUNDS. When heated to decomposition it emits acrid smoke and irritating fumes. 

CONSENSUS REPORTS lARC Cancer Review Group 2B IMEMDT 52,363,91 Human Inadequate Evidence IMEMDT 52,363,91. Reported in EPA TSCA Inventor). Cobalt and its compounds are on the Community Right-To-Know List. EPA Extremely Hazardous Substances List. OSHA PEL TWA 0.1 mg(Co)/m3 ACGIH TLV TWA 0.1 mg(Co)/m3 SAFETY PROFILE Poison by inhalation and intraperitoneal routes. Questionable carcinogen. Decomposes in air to form a product that ignites spontaneously in air. When heated to decomposition it emits acrid smoke and fumes. See also CARBONYLS and COBALT COMPOUNDS. 

NIOSH REL (Beryllium) CL not to exceed 0.0005 mg(Be)/m3 (Cobalt) Insufficient evidence for recommending limit SAFETY PROFILE Confirmed carcinogen. See COPPER, BERYLLIUM, and COBALT COMPOUNDS. When heated to decomposition it emits very toxic fumes of BeO. 

ACETIC ACID, COBALT(II) SALT (71-48-7) Co(CjH30j)i 4HOH Noncombustible solid. Solution in water is basic (pH 6.8 to >7.0) reacts with acids. Some cobalt compounds react with oxidizers, acetylene. Cobalt is a known animal carcinogen. ACETIC ACID, CUPRIC SALT (142-71-2) Cu(C2H302)i H20 Noncombustible solid. Solution in water is basic reacts with acids. Incompatible with acetylides, hydrazine, nitromethane, mercurous chloride nitrates, sodium hypobromite. Thermal decomposition releases fumes of copper, acetic acid, and carbon oxides. 

The activation entropy for thermal decomposition of /ra j -[MnX(CO)3(PPh3)2] indicates that manganese-phosphorus bond breaking is rate-determining. The rate law for the decomposition of CoH(CO)4 to Co2(CO)8 plus hydrogen is second-order in cobalt compound. While this decomposition has previously been studied in the gas phase, this is the first report of decomposition kinetics in the liquid phase. The first step in reaction of Co2(CO)s with organomercury halides is solvent-induced disproportionation of the dimeric carbonyl. ... 

Since ambient cure is desirable, cure of polyester gel coat systems is commonly catalyzed with the addition of a cobalt compound to facilitate hydroperoxide decomposition and, consequently, lower temperature cure. 

The palladium complex, [Pd(PPh3)4], was found to catalyze the decomposition of r-BuOOH in chlorobenzene at 35 °C [337], The rate of oxygen evolution was found to be directly proportional to the catalyst concentration. The rate of radical production (R ) was measured by the inhibition method [338] using 2,6-di-f-butyl-4-methylphenol. The chain length of the reaction [d02ldt/Rr] was found to be 10 in agreement with other studies [339,340]. Thus, decomposition is a normal radical induced reaction as in the case of catalysis by cobalt compounds. 

Cobalt difluoride [10026-17-2] C0F2, is a pink solid having a magnetic moment of 4, 266 x 10 J/T (4.6 Bohr magneton) (1) and closely resembling the ferrous (Fep2) compounds. Physical properties are Hsted in Table 1. Cobalt(II) fluoride is highly stable. No decomposition or hydrolysis has been observed in samples stored in plastic containers for over three years. 

The important (3-stabilizing alloying elements are the bcc elements vanadium, molybdenum, tantalum, and niobium of the P-isomorphous type and manganese, iron, chromium, cobalt, nickel, copper, and siUcon of the P-eutectoid type. The P eutectoid elements, arranged in order of increasing tendency to form compounds, are shown in Table 7. The elements copper, siUcon, nickel, and cobalt are termed active eutectoid formers because of a rapid decomposition of P to a and a compound. The other elements in Table 7 are sluggish in their eutectoid reactions and thus it is possible to avoid compound formation by careful control of heat treatment and composition. The relative P-stabilizing effects of these elements can be expressed in the form of a molybdenum equivalency. Mo (29) ... 

Even very small amounts of transition-metal ions like cobalt, nickel, and copper cause rapid decomposition. They form reactive intermediates that can decrease the stabiUty of oxidizable compounds in the bleach solution and increase the damage to substrates. Hypochlorite is also decomposed by uv light (24,25). Acidic solutions also lose available chlorine by the reverse of equations 1 and 2. 

Some metal carbonyls, such as nickel, cobalt and manganese compounds have been used to produce metallic deposition. The decomposition occurs in a stepwise manner, producing one CO(g) molecule at each step. 

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