1015] on Science and Industrial Problems p>25 



been achieved ? Simply by systematic " compound making " on the 

 part of hundreds of highly trained organic chemists. 



As it had been shown that the introduction of the hydroxyl 

 group into the molecule of anthraquinone gave rise to a colouring 

 matter, organized science at once became inquisitive, and was 

 anxious to know if the hydroxyl group was the only grouping which 

 was capable of producing this result. If not, what other groups had- 

 similar effects ? Was a variety of colours produced by the intro- 

 duction of different groups ? Did the number and position of these 

 groups in the molecule give rise to marked differences of shade in 

 the resulting dye stuffs ? 



Answers have been supplied to all these questions in a manner 

 which fills a chemical soul with nothing but admiration. Such work 

 has cost thousands upon thousands of pounds, provided largely by 

 manufacturers who, while not seeing any possibility of immediate 

 return for their money, still appreciated to the fullest possible extent 

 that pure scientific research work, carried out in the laboratory, is 

 the soul of industrial prosperity. 



In the first place the methods by which the following- groups 

 could be introduced into the anthraquinone molecule were fully 

 investigated : — 



CI, Br, NO,, OH, SH, NH,, NHCH3, NHOeH, ; 



and, secondly, the influence on. the shade or colour of the substance 

 resulting from the introduction of one or more of these groups into 

 different positions in the anthraquinone molecule. As a result it has- 

 been definitely proved that the colour of a derivative of anthra- 

 quinone depends on two factors : — 



1. The nature of the substituting groups. 



2. The number and position of these groups. 



The influence of the substituting group is shown by the fact that 

 on introducing in the para position to the amino group, in amino- 

 anthraquinone, a chlorine atom, a nitro or a methoxy group, little or 

 no effect is produced, so that the following substances have all an 

 orange or brick-red colour : — 



CO NHo CO NHo 



000 000 



CO CO Cl or NOo oi" OCH3 



Orakge to Brick-Red. 



But when a hydroxyl group enters the molecule, para to the amino- 



