j8 Appendix. 



The phenols are formed by substitution of OH for H at- 

 tached directly to the C of the ring. The first phenol, known 

 ..-■... as purest grade of carbolic acid, is obtained 



by gentle decomposition of many plant con- 

 stituents. Cymophenol, C,j,Hj30H, is 

 i found in the oil of thyme, from the Gym- 



j nospermae. Of the diatomic phenols, pyro- 



..- catechin, Cr,H4(OH)2, is readily obtained 



from tannins by distillation and exists read\ 

 ■ OH formed in Ampelopsis Hederacea. Creo- 



sote, obtained by destructive distillation of many bodies, con- 

 tains two homologous phenols, diatomic and triatomic, each 

 bearing methyl : 



Guaiacol, C7H|^02 = C,jH^ [ OH '* 



) CH,, 

 Creosol, C,H,oO., = C«H, V O. CH, 

 ' ) OH 



Pyrogallol (pyrogallic acid, largely used as a deoxidizing agent 



by photographers) is a triatomic phenol, C6H:j(OH)3, and is 



readily formed from tannins and from gallic acid ; while its 



isomer, phloroglucin, is obtained from resins and from glucos- 



ides by heating with potassa. 



The orcins, isomers of C^H^O^, substitutions of two mole- 

 cules of hydroxyl and one of methyl for three atoms of hydro- 

 gen in benzene, are found ready formed in lichens. The dyes 

 archyl, cudbear and persio contain orcins, — as also litmus, from 

 Leconora Tartarea. Aloes, treated with potassa, yields orcins. 



And now, in 1872, Schiff ascribes \.o gallic acid, C,HyO-,, a 



rational formula consisting of the introduc- {nS^ 



\ \ OH 

 tion of one carboxvl and three hydroxyl „ ' 



C ,; H 3 < U H 



molecules in place of tour of the hydrogen 1 qjj 



atoms of benzene." Farther, he presents and [OH 



maintains a rational formula for fermentable tannic acids, the 

 natural source of gallic acid.'" Having at last synthesized tan- 



(9) Ann. Chem. Phar., clxiii, 209 ; Jour. Chem. Soc, 1H72, 820. 



(10) Jolir. Chem. Soc, 1872, 215, 1019, 1098, ; 1874, 267. 



