ACHIEVEMENTS OF CHEMICAL INDUSTKY — DUISBERG. 243 



aside from carbolic acid, the aromatic hydrocarbons, l)enzole and its 

 homologuos, toluol and xylol, naphtalene and anthracene, play the 

 greatest part. 



I\lore recently carbazol has been isolated from tar on a large scale 

 and has become a most important raw material for the manufacture 

 of the color "hydronbluo" l)y Ivcopold Cassclla & Co., Frankfort on 

 the ]\Iain. Hydronblue is a sidphur dyestuff distinguished by its fast- 

 ness against wa,shing and chlorine. Acenaphthen, which also occurs 

 in coal tar as such, is the startmg material of a red vat dye "cibanon- 

 red," discovered by the Society of Chemical Industry hi Basle. It is 

 to be regretted that hitherto no technical use has been found for 

 phenanthrene, which is also one of the constituents of tar. 



Besides carbolic acid, its homologues, the various cresols, etc., are 

 being isolated by Dr. F. Raschig m Ludwigshafen on the Rhine. 

 These substances are largely employed in the manufacture of explo- 

 sives and coloring matters. 



As long as coal gas is produced for ilhnnmatmg and heating purposes 

 and as long as coke must be used for the reduction of u'on ores, tar 

 will alwa3''s remain the cheapest raw material for the manufacture of 

 these hydrocarbons. But smce it may become necessary in the 

 future — -as is already possible to-day — to use coal in a more rational 

 way, at the same time producing hydrocarbons, the coal-tar color 

 industry need not fear a scarcity of this miportant raw material, the 

 less so as certain kinds of petroleum, e. g., Borneo petroleum, contain 

 large quantities cf aromatic hydrocarbons from, which the Rheinische 

 Benzmwerke, m Reisholz near Dusseldorf, has already isolated 

 toluene m the form of nitro-toluene m a commercial way. If, how- 

 ever, a still greater demand for these hydrocarbons shoidd occur, other 

 methods of obtainmg them must be found. We shall then surely 

 succeed in producing them synthetically either directly from the 

 elements carbon and hydrogen or mdirectly from carbide of calcium 

 by passing acc>tylene through glowmg tubes — a reaction which was 

 already carried out successfully m the early sixties of the last century 

 by Berthelot and recently by Richard Meyer. At the present time 

 about one-quarter of Germany's annual output of coal is converted 

 mto coke, viz, 20 per cent for foundry purposes and 4 per cent in gas 

 works, whilst ui England the quantities are 12 per cent and 6 per 

 cent, respectively. 



DISTILLATION OF TAR. 



The point of greatest importance in the distillation of tar is still the 

 separation and isolation, in the cheapest possible way, of the different 

 hydrocarbons in their purest form. The stills have been continually 

 enlarged, those employed to-day having a capacity of 60,000 to 

 80,000 liters (13,000 to 17,500 gallons). On the other hand, a con- 



