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Home >> Chemistry Dictionary >> Coal Bituminous Coherant Precipitate
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Coal, bituminous. A solid fossil fuel of the plant origin, colour black or black grey. Having 75% to 97% carbon. It finds use as a fuel and as a raw material in the chemical industry.
Coal fossil. A general term for solid fuels of the plant origin such as peat, lingnite, bituminous coal, anthracite etc.
Coal gas. A fuel gas which is produced by the destructive distillation of coal. Typically it contained hydrogen (50%) methane (35%) and carbon monoxide (8%). By products of the process were coal tar and coke.
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Coal tar. A tar obtained from the destructive distillation of coal. Formerly, coal tar was obtained as a by product in manufacturing coal gas. Now it is produced in making coke for steel making. The crude tar contains a large number of organic compounds, such as benzene, naphthalene, methylbenzene, phenols, etc., which can be obtained by distillation. The residue is pitch. At one time coal tar was the major source of organic chemicals, most of which are now derived from petroleum and natural gas.
Cobalamin. See cobalt, organic derivatives.
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Cobalt. Co. At. No 27, at.wt. 58.9332, m.p. 1495ºC, b.p. 2870ºC, d8.92. Obtained commercially from silver ores (arsenides and sulphides) and Ni, Cu and Pb arsenide ores (speisses). Smaltite CoAs2, and cobaltite, CoAsS are also used as sources. The ore is roasted and Co is precipitated as the hydroxide and then reduced to Co with carbon (help below 417ºC, ccp to m.p.). The metal is silvery white and readily polished. It dissolves in dilute acids and is slowly oxidized in air. Adsorbs hydrogen strongly. The main use of cobalt is in alloys. Cobalt compounds are used in paints and varnishes, catalysts. Cobalt is an essential element in the diet.
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Cobalt alloys. Up to 80% of cobalt is used alloys, 20% of this for magnets. The most important cobalt alloys are stellite (up to 30% Cr, 18% W, 2 ½% C used in values and cutting tools) and vitallium (20% Cr, high temperature uses.) Co is also used in high-speed tools.
Cobalt oxides. Cobalt (II) oxide, CoO. Olive green solid (heat on Co (OH)2 or cobalt (II) oxyacid salt in absence of air) with Nacl structure.
Tricobalt tetraoxide, Co3O4. Black solid (ignition of CoO in air) Has spinel structure and other spinels MCo2O4 are also known.
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Impure CoO2 (oxidizing agent on alkaline Co (II) and some mixed oxides of cobalt (IV) and (V), e.g. K3CoO4, are known.
Cod-liver oil. Oil expressed from the fresh liver of the cod. It is a pale yellow liquid, slightly soluble in alcohol but miscible with organic solvents. It contains about 1000units of vitamin A activity per g and about 100 units of antirachitic activity (vitamin D) per g. It is a valuable source of the above vitamins and other food factors and is used in the prevention and cure of rickets in growing children.
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Coenzyme (Co-factor) : A substance which is required along with the enzyme if an enzyme-catalysed reaction is to occur.
Coherent precipitate. A precipitate in a solid alloy system which is still bonded directly to the parent lattice and does not have a distinct grain boundary. Generally associated with high strength in the alloy.
Coke. A form of carbon made by the destructive distillation of coal. Coke is used for blast-furnaces and other metallurgical and chemical processes requiring a source of carbon. Lower-grade cokes, made by heating the coal to a lower temperature, are used as smokeless fuels for domestic heating.
Coking. Relatively severe cracking processes converting residual materials such as pitch or tar into a mixture of gases, naphtha, kerorine, gas oil and coke. The gas oil is used mainly as feedstocks for catalytic cracking.
Coking coal. Coal which, after carbonization, will give a marketable coke.
Colemanite. CaB3O4(OH)3, H2O. An important source of borates.
Colligative properties. Properties that depends on the concentration of particles (molecules, ions, etc.) Present in a solution, and not on the nature of the particle. Examples of Colligative properties are osmotic pressure (See osmosis), lowering of vapour pressure, depression of freezing point, and elevation of boiling point.
Colloidal system. Any system consisting of a colloid distributed throughout a dispersion medium, e.g., milk, foam, aerosols.
Colloids. The particles dispersed in a dispersion medium with a size ranzing 10Aº to 2000ºA. The colloided solution is heterogeneous, scatter light, having charge and moves in all directions (Brownian movement), i.e., Zig-Zag motion.
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