The Romance of Modern Chemistry

VALUABLE SUBSTANCES The share borne by the residuals in defraying the cost of making coal gas has an important bearing on the question of gas versus electricity for lighting purposes. No doubt electricity has replaced gas to a considerable extent, but apart from the fact that gas is now largely employed for heating, the constant discovery of new uses for the by-products of gas manufacture tends to cheapen the cost of production. For long after the introduction of coal gas the tar was a nuisance, a disagreeable by-product the removal of which involved the manufacturer in considerable expense. The demand for it was exceedingly small and far short of the quantity which was turned out of the gasworks. Two men who carried on the distillation of tar in these early days have left it on record that the gas company gave them the tar on condition that they removed it at their own expense. The volatile spirit or “naphtha,11 which these two workers got by distilling tar, was employed by Mr. Mackintosh of Glasgow in dissolving indiarubber for the manufacture of the waterproof material which bears his name. In 1838 a patent was taken out for impregnating or “ pickling ” wood with heavy oil from coal tar, and this proved an important outlet for the gas manufacturer's refuse. Wood that has to be exposed to the action of water or to a moist soil will last much longer if it is steeped in this creosote oil; and for the treatment of railway sleepers, telegraph poles, and wooden beams for harbour works, &c., it is extensively used even at the present day. For the naphtha, however, which was distilled out of the tar before it was used for pickling timber there was a very limited outlet Some was used for dissolving 283