In an article which appeared in this _Journal_ in August 1876, entitled _The Age of the World_, we endeavoured to explain how coal was produced, and how it might be regarded simply as stored-up heat and light, derived from the sun ages ago.
Apart from the varied uses of coal in its ordinary state, we owe an immense deal to the products which by chemical means we obtain from it; and it is our purpose in this paper to briefly review these products, and to shew how we have adapted them to our several wants.
The manufacture of gas is undoubtedly the most important feature in the modern history of coal. Natural reservoirs of inflammable air exist in many parts of the world, and have in many cases been turned to profitable account. In China, for instance, the evaporation of salt has for many years been carried on by the heat obtained by the combustion of gas which issues from the ground. Streets and buildings there have also been lighted by the same means. In our own country too, such eruptions of natural gas—which have generally manifested themselves during the operation of well-boring—have not been uncommon. But the gas so obtained is not the same as that which we get from the distillation of coal, although it forms one of its chief constituents. It is commonly called marsh-gas, from its constant presence in bogs and places where decaying vegetable matter abounds. The treacherous Will o’ the Wisp owes its origin to this gas. It also issues in large quantities from coal-beds, and diluted with air forms the dreadful compound called ‘fire-damp.’
The first recorded experiment relating to the production of true coal-gas was as early as the year 1660, when a country clergyman distilled some coal, collected the gas in bladders, and burnt it from a jet, for the amusement of his friends. Although this very suggestive experiment was communicated to the Royal Society, no action seems to have been taken upon it until the beginning of the present century, when the matter seems to have attained a more practical form. At this time one or two factories in Manchester and Birmingham were for the first time lighted with gas. The idea of illuminating an entire town by means of a chemical vapour seems to have met with much ridicule, and it was found necessary to employ lecturers to go about the country to shew people how such an apparent impossibility could be carried out. However, in spite of much opposition, part of London was lighted by gas in 1812; and three years later, Paris adopted the same system. The delay in the acceptance of gas-making among the industrial arts was no doubt largely due to the expressed opinion of several eminent chemists and others, who considered that such a mode of lighting our towns could never be realised, because of the supposed danger which it involved. Modern experience teaches us that it is at once the cheapest as well as the safest mode of illumination that we can as yet command. In the manufacture of gas, the coal is placed in iron retorts, which are subjected to a high temperature for about six hours, when the operation is finished, and the retorts are ready for a fresh charge. A residue of nearly pure carbon, in the form of coke, remains in the retort, whilst the varied products of the distillation are carried off by pipes into suitable receptacles. For the sake of convenience, we will at present name only three of these products—ammoniacal liquor, tar, and the gas itself. The first is the principal source of ammonia, one of the most useful substances known. It may be almost said of ammonia, as it has been remarked of sulphuric acid, that the prosperity of a country may be known by the quantity which it consumes. It is used by colour-makers, calico-printers, and in the manufacture of most of the textile fabrics; in cleansing and extracting grease from various kinds of cloth, in the preparation of leather, in galvanising iron, and in pewtering. The chemist would be almost helpless without its aid; whilst in medicine it is used in about twenty different forms as a most valuable stimulant. It is almost needless to say that ammonia was in general use long before the era of gas-manufacture, for life could hardly go on without it. In fact its very name is derived from its manufacture hundreds of years ago from animal refuse in a district of Libya where the deity Jupiter Ammon was worshipped. The old alchemists too obtained it from the distillation of deer’s horns; hence one preparation of it is still called spirit of hartshorn. There are many other sources of ammonia, for its presence in nature is universal; but all have sunk into insignificance since the gas-works have yielded such plentiful supplies.