Page:Popular Science Monthly Volume 90.djvu/890

 The Wonders of Coal Tar

No branch of industrial chemistry yields more widely appli- cable and varying products than the distillation of coal

By George M. Oaks

��IF you have ever tried to run a furnace you know that coal gives off gas when heated. Yes, and you probably know that most of our illuminating gas comes from coal in that way. In by-product coke ovens the coal is heated in closed vessels so that the coal is distilled and not burnt up. But did you realize that this is the basic operation leading to hundreds of common, everyday products: tar, coke, lampblack, creosote, carbolic acid, naphtha, sal-am- moniac, ammonia, varnish, photographic materials, explosives, drugs, mineral van- illa, dyes and many others?

Coal, when heated, is chemically dis-

��membered to form several new substances which can be recombined or united with other substances to form new products. A toy house, made out of a child's building blocks, can be taken apart and a new house built, either out of the same blocks or by adding others. This process, it should be borne in mind, is a mechanical one, and only serves to illustrate in a simple way the distillation of coal, which is a chemical process.

Synthesis, or the process of building up new products from simpler ones, is best illustrated in making dyes. There are now so many shades of the same color that we

���Coal is a precious mineral. Its value can be better appreciated by noting some of the products such as dyes, explosives, drugs and perfumes, obtained directly or indirectly from its distillation

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