TECHNOLOGICAL CHEMISTEY WITT. 259 



extent by the far-reaching transformation of the gas industry, which, 

 on account of extended and ingeniously interpreted experiments had 

 been developed into an entirely new process, characterized by the 

 employment of high temperatures of distillation. The momentary 

 embarrassment which fell on the dj^e industry led to the creation, 

 far-reaching in its consequences, of a new industry — distillation for 

 coke, which saA-es from destruction the riches contained in the bj^- 

 products of coke manufacture and which frees for a long time the 

 dye industry from any lack of raw materials. 



Among the products derived from coal tar may be mentioned 

 anthracene, carbazol, the xylenes and the cresols, coumarone and 

 pyridine, substances whose systematic manufacture is onh^ forty 

 5'ears old and which have found a steady commercial application. 

 Of many of the other of the tar derivatives, some have been only 

 recentl}^ discovered, while others have been rendered more available 

 than heretofore. 



It is to the improvement in its methods of operation, especially in 

 the apparatus, that the industr}' of tar distillation owes the thorough- 

 ness with which its products may be separated from such a complex 

 mixture as goes to make up tar. Column stills, filter presses, and 

 processes such as vacuum distillation are the means which have 

 enabled the modern tar industrj? to attain its present position. 



The most striking example of an industry working hand in hand 

 with scientific research, profitably applying all its results and in- 

 fluencing them in its turn, is afforded by the manufacture of coal-tar 

 colors. It is almost impossible to touch in these few words on the 

 most important stages of the triumphal progress of this industry. 



We may say that the foundation of the German Chemical Society 

 was coincident with the date when the newlj^ founded color industry 

 was emancipated from empirical methods and turned toward scien- 

 tific synthesis. The first great success obtained through this agency 

 was the creation of the alizarin industry, whose later development 

 has surpassed all expectations. The recognition of the close connec- 

 tion between constitution and properties of coloring matters found 

 its practical application in the introduction of azo dyes, which not 

 only brought into the industry an extraordinary variet}^ of colors, but 

 accustomed the dye chemist to develop almost quantitative methods 

 of work. In the group of phthaleins were found not only some of the 

 most striking coloring materials, but also some of the most permanent, 

 thus refuting the theory, not proved, but then current, that artificial 

 colors were ephemeral in the same proportion that they were brilliant. 

 Equally permanent dyes were found among the eurhodines, safra- 

 nines, oxazines, indulines, and thionines, the study of which is so 

 intimately bound up in that of nitrogen chains and the joining of 

 nuclei. The discovery by a mere chance of a fast alizarin blue, so 



