6 CHEMISTRY 



on research the German chemical works had per- 

 fected methods for manufacturing indigo from 

 coal tar products ; for this purpose sulphuric acid 

 in a more concentrated form than could be made 

 by the customary "chamber" process was required, 

 and German chemists developed a suitable process 

 for preparing so-called "fuming" sulphuric acid 

 by a "contact" process. The contact process had 

 been in use on a small scale in this country for many 

 years. A similar illustration is afforded by the 

 manufacture of artificial indigo, in which liquid 

 chlorine was required in large quantities ; a process 

 for preparing and liquefying this gas was worked out 

 on a -manufacturing scale by the Badische Anilin 

 und Soda Fabrik, and a very valuable scientific 

 contribution was made to our knowledge of liquid 

 chlorine by Dr Knietsch, a director of these works. 

 The familiarity which the German technologist 

 thus gained in manufacturing and handling liquid 

 chlorine, with the aid of which indigo was made 

 for dyeing our own naval uniforms, led directly 

 to the use of chlorine as an asphyxiating gas 

 during the present war. This particular instance 

 shows how, by the national neglect of such 

 pure chemical research as that directed towards 

 the manufacture of artificial indigo, England has 

 allowed Germany to destroy her once flourishing 

 indigo plantations, to make an inroad on her 

 sulphuric acid industry, and to gain a distinct, 

 if but temporary, military advantage. 



