191 5] B. Horowits 165 



No relationship seems to have been worked out with reference to 

 the influence of the position, of the " auxochrome " relative to that 

 of the " chromophore " group. In some cases when the two are in 

 the Ortho position with respect to one another, the intensity of color 

 seems most marked ; in others, exactly the reverse is noticed. 



Even this brief outline of Witt's theory suffices to show its many 

 shortcomings, though its suggestiveness cannot be questioned. In 

 1888 Armstrong put forward his quinone theory of color.''' In 

 some respects this theory has shown a distinct advance over Witt's 

 conception. Bearing in mind the fact that dyestuffs in general can 

 be reduced to their colorless leuco bases by the addition of hydro- 

 gen, Armstrong traced all these Compounds to colored quinone, and 

 its reduction product, hydroquinone : 



O 



li — > I 



I II TT I I 



HC /CH O \/ 



Y O« 



II 

 O 



and he came to regard ortho- and para-quinone as the parent 

 substances : 



II - 



There have been many objections to various phases of this 

 theory. Hartley,^ as a result of a careful study of absorption 

 spectra, concludes that color and change of structure do not neces- 

 sarily go hand in hand, nor is a quinoid nucleus essential in a colored 

 substance. Baeyer's studies of tri-phenyl methyl have led him to 

 similar conclusions, in contradistinction to Gomberg.® Silberrad^" 



7 Armstrong : Chem. Soc. Proc, 1888, iv, p. 27 ; 1892, viii, pp. loi, 143, 189, 194. 



^Hartley: Kayser's Handbuch der Spectroscopie, 1900, iii, p. 170; quoted by 

 Cohen, Organic Chem., 1913, ii, p. 364. 



^Gomberg: Jour. Amer. Chem. Soc, 1914, xxxvi, p. 1161. An excellent 

 critical review of this intricate question is given here. 



1° Silberrad : Jour. Chem. Soc, 1906, Ixxxix, p. 1787. 



