280 HISTORY OF CHEMISTRY. [LECTURE XIV. 



which was eventually furnished by E. and O. Fischer, 35 the way 

 having been prepared by Hofmann. 30 



The manufacture of other classes of dyes has also arisen 

 independently of this theory, although no doubt advanced by 

 means of it. Examples of these substances are the phenol 

 dyes, of which the first representative is rosolic acid, discovered 

 by Kolbe and Schmitt 3 " and simultaneously J. Persoz ; 3S and 

 this group was greatly enlarged by the phthale'ines, discovered 

 and studied by Baeyer. 39 Other examples are the azo-dyes, 

 which are, almost without exception, connected with the im- 

 portant researches ot Griess. 



The influence which Kekule's conception of the aromatic 

 compounds exercised upon the views concerning the more 

 complicated hydrocarbons is much more direct. 



Erlenmeyer, 40 in an interesting paper on aromatic acids, 

 which contains a criticism of Kekule's views, assigns to naph- 

 thalene, C 10 H S , the formula : 



H H H H 



I I ! 



= cc=c c = c 



'- I i 



-H C C H 



II II 

 H C C H 



In accordance with this formula, naphthalene could be con- 

 ceived as composed of two benzene hexagons with two carbon 

 atoms common to both of them. Grabe rendered this concep- 

 tion very probable by means of experimental investigations and 

 theoretical considerations. 41 Aronheim's synthesis of naphtha- 

 lene from phenyl butylene 42 also tells in support of it, and so, 

 especially, does Fittig's synthesis of a-naphthol 43 (the hexagon 



35 Annalen. 194, 242. M J. pr. Chem. 87, 226 ; Jahresbericht 1863, 

 417; 1864, 819; Annalen. 132, 160 and 289. ^ Ibid. 119, 169. 

 38 French Patent, 2ist July 1862. <<J9 Annalen. 183, I ; 202, 36. 

 40 Ibid. 137, 327. 41 Ibid. 149, I. 42 Ibid. 171, 233. 43 Fittig and 

 Erdmann, Berichte. 16, 43 ; Annalen. 227, 242. 



