70 PROCEEDINGS OF THE AMERICAN ACADEMY 



which not only resembled naphtaline more closely than anthracene 

 did, but yielded diphenic acid and other undoubted derivatives of 

 diphenyl, and was therefore entitled to the first formula, leaving the 

 second for anthracene. This arrangement of the formulas was con- 

 firmed by Van Dorp's synthesis of anthracene from benzyltoluol, and 

 by some experiments by Graebe* which showed that phenanthrene- 

 chiuone gave diphenyl on distillation with soda-lime, while anthrachi- 

 none gave benzol and a very little diphenyl, indicating that there is 

 no direct union of the rings in the latter. 



Finally the syntheses from phtalic acid, and the formation of 

 phtalic acid by oxidation, or the action of sulphuric acid f on anthra- 

 chinone, established without doubt the ortho position of the connect- 

 ing atoms of carbon in one of the benzol-rings of anthracene, which 

 was still further confirmed by the syntheses from liquid benzyltoluol 

 and /8 benzoylbenzoic acid. 



At the end of 1873, therefore, the second formula had been uni- 

 versally adopted as that of anthracene, although the position of the 

 two connecting atoms of carbon in one of the benzol rings had not 

 been determined, and the researches of following years, while con- 

 firming the points already established, threw no more light on this 

 subject, t 



With phenanthrene the case is different, as the proof of the ortho 

 position of the two additional atoms of carbon has not been neglected. 

 In 1878 Schmitz § argued that this was probably the constitution 

 from the fact that diphenyleneketone and diphenylcarboxylic acid 

 were completely destroyed by oxidation ; while somewhat later in the 

 same year the poiut was proved by Schultz,|| and by Anschiitz and 

 Japp,l[ almost simultaneously. Schultz did this by converting Griess's 

 metadiamidodiphenic ** acid (made by the reduction of metanitroben- 

 zoic acid with tin and hydrochloric acid) into diioddipheuic acid, and 

 reducing this to a diphenic acid, which he proved was identical with 

 that from phenanthrene (a proof which he did not make perfectly 



* Ber. d. eh. G., 73, p. 63. 



t Weith and Bnidschedler, Ber. d. ch. G., '74, p. 1106. 



t Ajischiitz (Ber. d. oh. G., '78, p. 1213) made diphenyleneketone by heat- 

 ing antliracliinone witli calcic oxide, but proves in the same paper that this 

 reaction cannot be used as an argument in regard to the position of the C^Hj 

 group in anthracene. 



§ Ann. Chem. Pharm., cxctil. 115. 



II Ann. Chem. Pliarm., cxcvi. 1. Ber. d. ch. G., '78, p. 215. 



If Ber. d. ch. G., '78, p. 211. ** Ibid., '74, p. 1609. 



