The Romance of Modern Chemistry

NATURE’S STORES OF FUEL lignite. Peat, again, is vegetable matter—chiefly moss— which has been undergoing decomposition and carbonisa- tion for a very much shorter time, and which, being on the surface, has not been subjected to the same pressure as coal, and is therefore less compact. A few figures will show how the amounts of hydrogen and oxygen diminish regularly as we pass from wood to a hard coal like anthracite. To make the figures com- parable, the amount of carbon is put as equal to 100 in each case. Wood. . , Carbon. Hydrogen. Oxygen. . 100 12 83 Peat . . . 100 9 56 Lignite . . 100 8 42 Bituminous coal . . 100 6 21 Anthracite . . 100 3 2 Corresponding to the gradual alteration in composition, there is a change also in the way these fuels behave when they are burned. For a brightly blazing fire there is nothing like wood, the reason being that, when it is heated, quantities of inflammable gas are given off; hence wood catches fire much more easily than the other solid fuels, and when it has ignited it bums with a larger amount of flame, for flame is simply burning gas. The inflammable vapours given off from heated wood consist to a large extent of hydrocarbons—that is, compounds of carbon and hydrogen. Wood, therefore, which has undergone an age-long decay, and which has in the process lost the greater part of its hydrogen, will be able to yield little or no inflammable gas when heated. Take anthracite, for example—a species of coal which is largely mined in Wales; it contains a very high proportion of carbon, and 133