THE COAIr-TAR COLORS 1 



THE term "coal-tar colors" is applied to coloring matters 

 artificially prepared from coal-tar, chiefly from the hydro- 

 carbons extracted from it. 



The first observation of a colored compound of this class 

 was made by Runge in 1834; but the real beginning of the 

 great modern color industry dates from 1856, when W. H. 

 Perkin obtained a violet dyestuff by oxidizing impure ani- 

 line with chromic acid, took out a patent for it, and com- 

 menced manufacturing it in England. Many other dyes were 

 subsequently obtained from aniline and the substances related 

 to it, by A. W. Hofmann, Griess, Girard, Lauth, and many 

 others. But the most sensational step was the preparation 

 by Graebe and Liebermann (1868) of a natural dyestuff 

 viz., the coloring principle of madder-root from the anthra- 

 cene of coal-tar. In 1880 indigo was first prepared, not from 

 coal-tar products, but by a purely synthetic method, and other 

 natural colors have since been prepared in a similar manner; 

 so that natural dyestuffs reproduced by artificial means 

 need not necessarily originate from coal-tar. The artificial 

 indigo and alizarin are not mere substitutes for the natural 

 indigo and madder; they are chemically identical with them, 

 and surpass them in purity, and their adaptability to special 

 methods in dyeing and printing often makes them even more 

 desirable. But as the cost of manufacture is high, they com- 

 pete with the natural products on about equal terms. 



The color industry was first developed in England and 

 France, but the more thorough technical instruction at the 



1 Reprinted from the New International Encyclopaedia (Dodd. Mead & Co., New 

 York, 1912, 6, 74-77), by permission of the Publishers. 



