328 Professor Arthur W. Crossley [Feb. 5, 



desired colour, and if it had not previously been made, lie would 

 know exactly the series of reactions by which it could be manufactured. 



It sometimes happens that accident or luck, as it is erroneously 

 called by some people, jjlays a very important part in research work, 

 and the manufacturer of anthraquinone derivatives is again able to 

 provide an example of what importance a chance observation may be, 

 if only it is made by a trained chemist, who allows no fact to escape 

 him unexplained, and who has the necessary scientific ability to follow 

 up and master such occurrences. 



In the preparation of a colouring matter called " sky blue ahza- 

 rine " (III), it was customary to heat dibromaminoanthraquinone with 

 para-toluidine, when the following reaction took place : — 



CO XHo CO XHo 



COO" ■"' "" "'"CCO 



CO Br CO NH.CkH^ 



(III) 



On carrying out this replacement in a new apparatus, but other- 

 wise under exactly the same conditions as previously, none of the sky 

 blue alizarine was obtained, but an entirely different derivative. 



How w^as the explanation of this fact to be sought ? Surely it 

 could not possibly have anything to do with the new apparatus. 

 Investigation showed, however, that such really was the case, for 

 whilst the old apparatus was made entirely of iron, the new one had a 

 copper lid, and it was soon proved that the presence of the merest 

 traces of copper exerted a very great influence on the course of the 

 above reaction, resulting in the formation of a derivative of ind- 

 anthrene. 



1- HN CO C7H7.HN CO 



.ceo POO 



CO H^Hi; I CO 1 NH 



ceo 



Dr; 



CO NH.C^Hy CO NH.C7H7 



It may seem very interesting, and perhaps wonderful, that^the 

 course of the reaction was thus established, and that a method 

 was thereby devised for the synthesis of indanthrene derivatives. 



