^4 Appendix. 



I I 



c c 



// -^ / \ 



— C C C— 



I II I 



Anthracene Ci^Hj^ ^ ^ ^ 



or C„H,,„_;„« Triple '^ / \ -^ ^ 



Hexagon C C C — 



I I II 



-C C- 



■^ / 



c 



From these hydrocarbons (?. e., from the hexagon, single, 

 double or triple) all the aromatic bodies are extended. Displac- 

 ing (one or more atoms of) 



H by OH, phenols are formed (as in carbolic acid). 



^ ( OH, acids " " (as benzoic acid). 

 H) rOH 



>by- ^fO , acids " " (as salicylic acid \ 

 H j ( ^|0H 



HbyN|| 

 Hi "JO 



V V 



amines " " fas anilin). 



rby^ I 

 H ' ) O, quinones " " (as anthraquinone). 



The aromatic hydrocarbons have been looked upon as 

 bodies of too simple chemical construction to exist in plants, 

 and this is certainly true of the lighter portion of them. The 

 first three members of the benzene series are not found in the 

 vegetable kingdom, and the fourth, cumene, or trimethylben- 

 zene, has been reported found only in Roman cummin oil. But 

 the fifth member of the series, cymene, or tetramethylbenzene — 

 a body having the molecular weight 134 and hence in vapor 67 

 times heavier than its bulk of hydrogen — a liquid closely ap- 

 proaching both in composition and in properties to turpentine 



