The Romance of Modern Chemistry

THE VALUE OF THE BY-PRODUCT salt cake furnace. Weather permitting, the furnace was to be towed out to sea, and there allowed to do its worst, so far as pollution of the atmosphere was concerned. Gradually, as time went on, another method of dealing with the waste hydrochloric acid came into vogue. This gas is very easily soluble in water, so that by making it pass through a chimney or tower packed with coke over which water was constantly running, it was possible to absorb the greater part of the acid fumes. This was undoubtedly the right direction in which to go to work, but the absorption of the acid was never complete, and as the number of alkali works increased very rapidly, the public nuisance caused by the uncondensed acid vapours was as great as ever. It is estimated that even as late as 1860 the English alkali works were pouring out about a thousand tons of this corrosive hydrochloric acid gas every week. Besides, those manufacturers who went in for absorbing it were left with enormous quantities of the acid liquor on their hands. There was not much demand for this; it had little value, and the bulk of it was accordingly tipped into the nearest stream. Here the acid did fresh damage, for it killed all the fish; the people immediately concerned with the stream objected to its pollution, and complaints were very numerous. Altogether rather an awkward situation for the alkali manufacturers ! Yet within the space of a few years the whole aspect of affairs was altered. The hydro- chloric acid, which had been such an unmitigated nuisance to everybody since the start of the alkali industry, was discovered to be a valuable product. The alkali manu- facturer became very careful to keep and use every particle of the substance which a few years before he 275