Coal-Tar Industry. At the present time, this industry is in a state of high fever. Tar is the generic name for all that part of coal which does not remain behind as coke, on dis tillation, and which does not go through the gas into the gasometer. It consists of a large series of bodies, from benzole, which is lighter than water, to pitch. The pitch is used for roofing and very lately an American proc ess has been developed for coking it. The lighter bodies are used for preserving woods, and, with the still lighter ones, as the starting point for a vast variety of chemical products. These include the long list of coal-tar colors, explosives, photographic and pharmaceutical preparations, synthetic perfumery and innumer able other products.
Despite the great use of coal in the United States, the country has not been as large a producer of tar as might be expected, because petroleum water gas has been greatly used in cities, and this produces practically no tar. The coke for the iron industry (to our shame be it said) has been made chiefly in ovens of the so-called beehive type in which everything, all the precious content of the coal except the coke, is wasted. This condition is in process of correction; by-product ovens are rapidly supplanting the beehive type and the amount of available tar is increasing. At pres ent it is estimated that nearly one-half of the coke produced in the United States is still made in beehive ovens. Until the outbreak of the war, the principal use for tar in the United States was for some of the pitch, the other bodies being exported or used to enrich city gas or wasted. In fact, the light oils from nearly all coal tars found their way to Germany, if they were saved at all, for there was the great coal-tar color and product industry of the world. Then came the war, the closing of German ports and general anarchy of trade. Within an area the size of the State of New York a great part of the dye-stuffs, all of a certain kind of medicines, many pho tographic materials in fact, the bulk of the coal-tar product industry, was located. But the very same things needed to make dyes, etc., are needed to make munitions. The same raw materials are needed for both. What .the color maker wanted the explosives works needed, and the latter were willing toany price. This is what gave the by-product coke-oven industry, which was slowly developing in America, its rapid development. The coal-tar
industry has since then grown in the United States by leaps and bounds. At the outbreak of the war, there were six factories making dye-stuffs from intermediate products im ported from Germany. Now, after less than four years, there are nearly 100 concerns mak ing finished products with the old ones greatly enlarged, and over 40 factories making inter mediates. What the future of the industry will be when the demand for the lighter oils of tar for munitions ceases, it is hard to tell. Benzole, it may be recalled, is an excellent fuel for ex plosion engines and it will probably become a rival to gasoline.
Medicines. The advances made in physi ology in connection with physical chemistry have enabled intelligent physicians to compre hend the reactions which take place with many medicines, and thus to proceed with greater understanding and less doses. When the chemical structure and reactions of a body are known it is desirable that it be dispensed in a pure state, and this need has brought about marked improvements in pharmaceutical chem istry. Many synthetic bodies, built up under careful supervision and with knowledge of their structure, have supplanted indefinite decoctions made by extracting all the soluble juices of plants and letting them go as the concentrated extract of something chemically unknown.
Rubber. Synthetic rubber has been pro duced by causing certain hydrocarbons to polymerize, which is, in effect, to cause their molecules to join in large groups. But very little has been produced and in view of the im proved culture of gum-producing trees and plants, and the better harvesting of the latter, the question is still debatable whether the syn thetic product will replace the natural one, eco nomically, as was the case with indigo before the war.
Perfumes. A growing knowledge of the structure of the molecules of organic com pounds has enabled chemists to provide ethers and esters of great olfactory power and by mixing these to obtain odors desired. Musk and other standard perfumes are now produced synthetically in factories. The sense of smell, what olfactory phenomena are, and what their relation to life is, remains unstudied. The medieval Saracens were far ahead of us in the understanding of this sense.