Cobalt pyrophoric

Whereas finely divided cobalt is pyrophoric, the metal in massive form is not readily attacked by air or water or temperatures below approximately 300°C. Above 300°C, cobalt is oxidized by air. Cobalt combines readily with the halogens to form haUdes and with most of the other nonmetals when heated or in the molten state. Although it does not combine direcdy with nitrogen, cobalt decomposes ammonia at elevated temperatures to form a nitride, and reacts with carbon monoxide above 225°C to form the carbide C02C. Cobalt forms intermetallic compounds with many metals, such as Al, Cr, Mo,... 

This type of catalyst is not limited to nickel other examples are Raney-cobalt, Raney-copper and Raney-ruthenium. When dry, these catalysts are pyrophoric upon contact with air. Usually they are stored under water, which enables their use without risk. The pyrophoric character is due to the fact that the metal is highly dispersed, so in contact with oxygen fast oxidation takes place. Moreover, the metal contains hydrogen atoms and this adds to the pyrophoric nature. Besides the combustion of the metal also ignition of organic vapours present in the atmosphere can occur. Before start of the reaction it is a standard procedure to replace the water by organic solvents but care should be taken to exclude oxygen. Often alcohol is used. The water is decanted and the wet catalyst is washed repeatedly with alcohol. After several washes with absolute alcohol the last traces of water are removed. 

The boride precipitated from sodium borohydride and cobalt(II) chloride in methanol becomes pyrophoric after vacuum drying. It can safely be stored solvent-moist. 

Finely divided (pyrophoric) cobalt decomposes acetylene on contact, becoming incandescent. 

Cobalt catalysts discharged from oxo -process reactors are frequently pyrophoric, owing to the presence of the carbonylcobalt. 

Finely divided cobalt is pyrophoric in air [1], Raney cobalt catalyst appears to be less hazardous than Raney nickel [2],... 

Schmitz-Dumont, O. et al., Z. Anorg. Chem., 1941, 284, 175 Heating converts it to pyrophoric cobalt(III) nitride. 

Heat of combustion, thermal conductivity, surface area and other factors influencing pyrophoricity of aluminium, cobalt, iron, magnesium and nickel powders are discussed [4], The relationship between heat of formation of the metal oxide and particle size of metals in pyrophoric powders is discussed for several metals and alloys including copper [5], Further work on the relationship of surface area and ignition temperature for copper, manganese and silicon [6], and for iron and titanium [7] was reported. The latter also includes a simple calorimetric test to determine ignition temperature. 

Substances that catch Are spontaneously in air without an ignition source are called pyrophoric. These include phosphoms, the alkali metals and powdered forms of magnesium, calcium, cobalt, manganese, iron, zirconium, and aluminum—all of which may occur at one time or another at a refinery site. Moisture in air is often a factor in spontaneous ignition. 

Finely divided cobalt is pyrophoric. But the lump metal is stable in air at ordinary temperatures. It is oxidized on heating at 300°C to cobalt oxide. 

Caution. Decomposition of the cobalt carbonyl clusters produces CO, which is an odorless, toxic gas. The hexane solution of ZnEt2 is convenient to handle, but is a source of ZnEt2, which is a pyrophoric and volatile liquid. Handling these compounds in a well-ventilated hood and wearing eye protection are recommended. 

Tetramethylisoindole See 1,3,4,7-Tetramethylisoindole Cobalt See other METALS, pyrophoric metals... 

Pyrophoric Cobalt was described by Magnus in 1825,7 who prepared it by reduction of its oxides in a current of hydrogen. The best temperature of reduction 8 appears to be 250° C. If the reduction is effected at 700° C. the cobalt is not pyrophoric. Pyrophoric cobalt is a black powder, which bums brilliantly when exposed to the air in consequence of rapid oxidation. 

When obtained in a finely divided state by reduction of its oxides at 250° C. cobalt is pyrophoric. In this condition it decomposes acetylene in the cold, the metal becoming incandescent. A portion of the acetylene polymerises to benzene, whilst the remainder yields carbon and hydrogen.9... 

Occurrence of Cobalt—History—Preparation—Pyrophoric Cobalt—Physioal Properties—Ooelusion of Hydrogen—Chomioal Properties—Atomic-Weight —Uses -Electro-deposition—Alloys. 

Dimethylbismuth chloride Dimethylcadmium Dimethylmagnesium Dimethyl mercury Dimethyl-phenylethynylthallium Dimethyl-l-propnylthallium Dimethylzinc Ethoxydiethylaluminium Methylbismuth oxide Methylcopper Methyllithium Methyl potassium Cobalt Hafnium Iridium Iron Lead Lithium Manganese Nickel Palladium Platinum Plutonium Potassium Pyrophoric alkyl non-metals Hydrides Dietbylarsine Diethylphosphine Dimethylarsine 1,1 -Dimethyldiborane 1,2-Dimethyldiborane Dimethylphosphine Ethylphosphine Methylphosphine Methylsilane... 

Elemental cobalt is relatively luireactive in air at ambient temperature, although the finely divided metal is pyrophoric. Cobalt is oxidized on heating in the presence of oxygen to give... 

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