ACHIEVEMENTS OF CHEMICAL INDUSTRY DUISBERG. 245 



being more and more employed. Several decades ago it l^ecame 

 an important substance for tlie production of the urea of para- 

 amidobenzolazo-salicjdic acid, introduced into the market under 

 the name of "cotton yellow," <ns a beautiful yellow cotton color 

 of great fastness to light. It's principal use, however, was for the 

 manufacture of the bright but fugitive triphenylmethane colore. 

 It is now especially used to combme two molecules of aromatic com- 

 pounds with free amido groups, thus producing urea derivatives, 

 and if the starting material is an azo color, the resultuig urea deriva- 

 tive is, as a rule, much faster to light than the original color. Imi- 

 dazol, thiazol, and azimido compounds of the most varied kinds are 

 also manufactured and converted mto azo colors. 



In the series of the aldehydes and carboy3dic acids there are no 

 epoch-makuig discoveries to ])e recorded. Chemists still start from 

 hydrocarbons chlorinated in the side chain or dhectly oxidize the 

 homologues of benzole. Klobe's synthesis of salicylic acid, of which 

 large quantities are used in the color industrv, is also applied at an 

 ever-increasing rate for the i)roduction of the oxycarboxjdic acids. 

 But the direct introduction of the carl)0X3dic group into the benzole 

 molecule, unsubstituted by hydroxyl, is a greatly desired achieve- 

 ment, which, however, has not yet been attamed. It is also a matter 

 of greatest importance that in substitution reactions of the aromatic 

 nucleus we should be able to vary at will the ratio of the isomers 

 to be formed. 



Besides the biochemical production of ethylic alcohol from wood 

 waste and from the waste liquors of the sulphite cellulose industry, 

 I wish to mention the synthesis of organic compounds by the addi- 

 tion of water to acetylene. In this manner we produce in a simple 

 way acetaldehyde, which can be easily converted into acetic acid, 

 a very^ important starting material for the manufacture of munerous 

 products. 



The steady search for new raw materials and new intermediate 

 products to be utilized in the manufacture of colors has often been 

 crowned with success. We need only to recall the many mterme- 

 diate products which have Ijcen made available for the ])roduction 

 of the vat dyes and sulphur colors and which have led to the dis- 

 covery of new substances M-itli most valuable properties. Very often 

 new Imes of research are not always based upon preconceived theo- 

 retical ideas, but are opened u]) ])y mere accident. A keen ])ower of 

 observation, however, is the most necessary equipment of the chemist 

 who aims at success. 



COAL-TAR COLORS. 



In no l)raTich of technical chemistry has such intense work been 

 performed as in that of the coal-tar color industry. The outsider long 

 85300°— SM 1912 17 



