282 HISTORY OF CHEMISTRY. [LECTURE XIV. 



mont, 49 by Baeyer and Caro, 50 and by Piccard, 51 since it brings 

 out plainly the relations between phthalic anhydride and 

 anthraquinone. 



Further, the constitutions of fluorene, fluoranthene, chry- 

 sene, and retene, as well as their relations to benzene, are now 

 cleared up. Fluorene, C 13 H 10 , discovered by Berthelot, 5 ' 2 is 

 obtained by Fittig 53 by the distillation of diphenylketone with 

 zinc dust, and is thus recognised as diphenylene methane, 



)CH . Fluoranthene (idryl), C 15 H 10 , isolated by 

 C 6 H/ 



Goldschmiedt 54 from a semi-solid by-product obtained during 

 the distillation of the ores of mercury at Idria, and also occur- 

 ring in coal tar, 55 is probably represented by the formula 



CH-CH 



Chrysene, C 18 H 10 , is recognised, from a synthesis of it 



C (i H 4 CH 

 effected by Grabe, 56 as a naphthalene-phenanthrene 



that is to say, as phenanthrene in which one of the phenylene 

 groups is replaced by a naphthalene group. Finally, retene, 

 C 18 H 18 , according to the investigations of Bamberger and 

 Hooker, 57 is a methyl-propyl-phenanthrene 



CH C 6 H 4 



II I CH 



/"TT (~* TT ^ n 3 . 



V>. V^ G IT.Oy~( -WJ 



Hence, it can scarcely be doubted that the other hydro- 



49 Berichte. 5, 908. r>0 Ibid. 7, 972; 8, 152. 51 Ibid. 7, 1785. 



52 Annalen. Supplementband 5, 371. 53 Berichte. 6, 187; Annalen. 



193, 134. 54 Berichte. 10, 2022. 55 Fittig and Gebhard, ibid. 



IO, 2143; Annalen. 193, 142; Fittig and Liepmann, ibid. 2OO, I. 

 56 Berichte. 12, 1078. r ' 7 Ibid. 18, 1024 and 1750; Annalen. 229, 102, 



