Anthracene, when oxidized, yields anthra quinone, from which is obtained alizarine, and thence the whole large group of alizarine dyes. The fluid remaining after washing the light oils with sulphuric acid contains pyridine, and the other bases — the picolines, lutidines, etc. Ammonia gas is run into the liquid until the pyridine separates—as an oil. Quinoline is separated in the same way from the sulphuric acid washing of the heavy oils. It is used in making indigo.
These secondary products yield, besides the coal-tar colors, an extended list of medicinal drugs, perfumes, flavorings, disinfectants and preservatives, burning and lubricating oils, pig ments, photographic chemicals, etc. Only a few of these can be mentioned here.
From benzol are derived nitrobenzene, yield ing aniline and thence the aniline colors; ery throsine, used to render photographic plates orthochromatic; fluorescine, used in testing the purity of drinking waters; the flavoring °bitter almond oil," and a similar perfume; acetanilide, the basis of headache powders; and the hyp notic, acetophenone.
From toluol are derived the preservative ben zoic acid, and its salts; picric acid, trinitrotoluol and other high explosives; the benzaldehydes, and others; and the drug saccharine, 300 times sweeter than sugar.
From phenol come nitrophenol, and the amidophenol dyes; coumarin, the artificial vanilla flavoring; carbolic acid, the surgeon's sterilizer; and salicylic acid and its medicinal salts.
Xylol is the source of xylidine scarlet and other dyes.
Naphthalene yields naphthol and amido naphthol dyes; is vaporized to enrich and add to the brilliancy of coal-gas; and is burned to produce a high grade of lamp black.
From quinoline come antipyrine and other antipyretic medicines, and the photographic de velopers, hydroquinone, eikonogen, etc.
The pitch which forms 50 per cent of the bulk of coal-tar is the base of many water proofing and paving materials, and the source of most artificial asphalt.
When the European War broke out in August 1914, there were in the United States six factories making coal-tar colors. They employed about 400 operatives, and manufactured annually about 3,300 short tons of coal-tar dyes. The consumption in the United States was about 29,000 short tons, of which 22,000 tons came from Germany. At the close of 1915, there were 14 concerns mak ing finished dyestuffs in the United States, and a score or more making intermediates. Several of the larger textile mills also have established dye-making plants of their own. The aggre gate production for 1915 was about 15,000 tons, with a much larger output in sight for 1916. See CHEMISTRY, PROGRESS Or.
Bibliography.— Beacall, (Dyestuffs and Coal Tar Products> (1915) ; Gardner, 'The British Coal Tar Industry> (1915) ; Lewes, 'The Car bonization of Coal> (1912); Lunge, 'Coal Tar and Ammonia> (000); Wagner, 'Coal Gas Residuals> (1914) ; Warnes, 'Coal Tar Distil lation> (1913).