LECTURE XIV.] HISTORY OF CHEMISTRY. 28 1 



formula for benzene being assumed). This view concerning 

 naphthalene leads to the assumption of two isomeric mono- 

 substitution products. Faraday had, in fact, prepared two 

 naphthalene mono-sulphonic acids, 44 and many similar cases 

 have been observed since then. It has even proved possible 

 in the cases of naphthalene derivatives to carry out determina- 

 tions of the positions of the atoms with. a very high degree of 

 probability ; and here, also, after a detailed study of the naph- 

 thalene series, a marked agreement between fact and theory is 

 observed. 45 



Anthracene, the starting point in the preparation of so many 

 interesting compounds and valuable dyes, was early recognised 

 as a closed carbon chain, and as " a nucleus derivable from 

 benzene." Grabe and Liebermann, 46 in their first communica- 

 tion on the connection between alizarine and anthracene, pro- 

 posed a formula for the latter, in accordance with which it is 

 represented as tribenzene ; that is, as made up from three 

 molecules of benzene and as having four of its carbon atoms 

 common to two different hexagons. Besides this, in their 

 detailed paper they afterwards advanced another similar 

 formula for anthracene, which, however, seemed to them to 

 be less probable. After the discovery of phenanthrene (which 

 is isomeric with anthracene) and the special study of it, for 

 which we are indebted to the almost simultaneous investigations 

 of Grabe and Glaser 4r and of Fittig and Ostermeyer, 48 the first 

 anthracene formula was recognised as representing phenan- 

 threne and the second one was retained for anthracene. The 

 latter formula meets all requirements, and this is a matter 

 which is really astonishing, in view of the numerous isomerisms 

 in the anthracene group. It is also capable of giving a clear 

 representation of the neat syntheses of anthraquinone, alizarine, 

 quinizarine, and purpurine, effected by Kekule and Franchi- 



44 Phil. Trans. 1826, 140; Ann. Chim. [2] 34, 164. 45 Compare 

 especially Reverdin and Nolting, Ueher die Constitution cles Naphtalins, 

 Genf 1880; also Liebermann and Dittler, Annalen. 183, 228. 46 Berichte. 

 I, 49. 47 Ibid. 5, 86 1 and 968; Annalen. 167, 131. 48 Berichte. 

 5, 933; Annalen. 166, 361; compare also Hayduck, ibid. 167, 177. 



