What is COAL?

is supposed to be the residual product of the natural decomposition of forests and other vegetable matters during enormous periods of time, and is a very complex mixture of carbon compounds, containing generally some proportion of nitrogen. It is an indefinite and variable mixture of compounds insoluble in pyridine, cellulosic compounds soluble in pyridine but insoluble in chloroform, and another constituent of resinoid character which can be extracted by certain solvents, such as pyridine, and chloroform, while upon the relative proportion of these bodies the technical value and industrial applications depend. The following analysis of certain coals recently published by S. Roy Illingworth are given as some illustrations of their composition, which varies greatly: The No. 2 Llantuit coal is used for gasmaking and yields a very porous coke. The No. 3 Rhondda coal is carbonized to produce a metallurgical coke, which is dense. The No. 2 Rhondda coal is a “hardcoking” coal, and also yields a dense coke. Deposits of coal are tound in all parts of the world, and China is particularly rich, her coalfields being regarded as practically inexhaustible. It has been ascertained that coal undergoes oxidation by air, one experimental result, which has been published, showing a gain of 3*5 per cent, by weight in one month at ioo degrees C. Aniline used as a solvent is stated to furnish a moans of differentiating between grades of coal; the “fat” varieties yielding a relatively higher percentage of soluble matter as compared with the “lean” kinds. The soluble part is richer in hydrogen, poorer in ash, and gives a better coke than the insoluble part. There are many varieties, and they are roughly divided into hard and soft coals, the softer ones being used for fires and gasmaking, while the harder ones contain more carbon, give out more heat w hen burning, and are consequently mure useful for steam raising. Bituminous coal contains from 50 to 80 per cent, of carbon, and anthracite from 85 to 95 per cent. In burning, coal may be said to give back the heat and light which were originally taken from the sun by the plantlife from which coal is produced. When burned or roasted, the products of its destructive decomposition thus effected, vary according to the temperature employed and the proportion of air that gains access to the burning mass. It begins to yield free carbon at about 500 degrees C., although, of course, below this temperature decomposition proceeds, and it seems probable that the formation of this free carbon is due to the decomposition of the cellulogic constituents of the coal. About igo million tons of coal are annually consumed in the United Kingdom, of which about onefifth part is carbonized in gasworks or in cokeovens, and the total estimated output of coal in the United Kingdom in 1919 was about 230 million tons. As used for gasmakingso that it is not allowed to burncoal yields, in addition to the gas, watery ammoniacal liquor and tar which pass over in a vaporous condition and are condensed, leaving coke in the retorts. The coal tar, which has a sp. gr. of about Il to i

Link to This Definition
Did you find this definition of COAL helpful? You can share it by copying the code below and adding it to your blog or web page.
Definition of  COAL