Britain at Work
A Pictorial Description of Our National Industries

98 BRITAIN AT WORK. generally at the station meter house—draws the gas from the retort through all its mazy windings, a steam-jet injector being also used as exhauster in some works. After being scrubbed, the gas is made to pass through thick layers of fresh slacked lime in tanks to free it from the evil-smelling sulphuretted hydrogen, bisulphide of carbon, and carbonic acid. Other substances beside lime are sometimes used, such as slightly moist iron oxide, mixed with sawdust, or chaff, to render it porous. The object which must be obtained, however, is to bring up the gas to the Parliamentary standard of purity. The freedom from sulphuretted hydrogen should be shown, not only by the absence of its very unpleasant odour, but by the fact that ten cubic feet of gas shall not show a stain on lead paper ; furthermore, not more than twenty-two grains of sulphur, or four grains of ammonia, must be traceable in a hundred cubic feet. Passing from the lime tanks, the gas goes to the station meter house, where it is measured, and where the pressure instruments are kept; it is then at last allowed to escape to those immensely large round gas-holders which form the most prominent object of any gasworks. These huge vessels are built over great tanks of water, and in them the gas is stored and kept ready for use. It is important to notice that the lime purifiers are so constructed that when one part is saturated with impurities, the stream of gas can be directed to a freshly renewed portion, while the impure lime is removed. Indeed, this principle applies throughout, the apparatus being so arranged that some parts can be thrown out of action while other parts are continuing the work. The ingenuity of chemists and of engineers has enabled manufacturers to increase the volume and enrich the illumination by the use of water-gas and of vapour from mineral oils. The combination of these two products is known as carburetted water-gas, and it may be said without exaggeration that the pre- paration of this compound now enters very largely into the manufacture of gas. And so long as the product is up to the Parliamentary standard of fifteen or sixteen sperm candles in illuminating power and is free from poisonous AT THE GAS LIGHT AND COKE COMPANY’S WORKS, BECTON.