The Romance of Modern Chemistry

CHAPTER XXV VALUABLE SUBSTANCES FROM UNLIKELY SOURCES THE last chapter will have shown the reader how waste products, sometimes merely embarrassing in their character, sometimes definitely obnoxious, can be brought to play their part in our industrial economy. We are encouraged to believe that everything has its place, could we but find it out, and that the waste material of our industries is frequently wealth in disguise. Perhaps in no case has the disguise been more complete than in the by-products of gas manufacture. Some reference has already been made to these in chapter xiii., but the lessons of the alkali trade may be suitably enforced by a study of the marvellous story of coal tar, and other equally unsavoury products of the gasworks. Here also science has shown how useful and beautiful substances can be obtained from the most unpromising material, and how so-called waste products can be made to contribute largely to revenue. The reader may remember that in the dry distillation of coal four products are primarily obtained, namely, coke, ammoniacal liquor, tar, and coal gas. Little more need be said about the coke and the gas except to point out again that even the sulphuretted hydrogen in the latter, which must be removed on account of its harmful character, is made to pay part of the cost of production. The 280