AROMATIC ACIDS AND THEIR DERIVATIVES. 297 



The preceding graphic formulas show that 



Benzene, C 6 H 6 , is a saturated hydrocarbon. 



Phenol, C 6 H 5 HO, is an alcohol obtained from benzene by replace- 



ment of one atom of hydrogen by hydroxyl. 



Picric acid, C 6 H 2 (N0 2 ) 3 HO, is phenol in which three hydrogen atoms are re- 



placed by three NO 2 . 



Nitro-benzene, C 6 H 5 N0 2 , is benzene in which one hydrogen atom has been 



replaced by NO. 2 . 



Aniline, C 6 H 5 NH 2 , is benzene in which one hydrogen atom has been 



replaced by N H 2 . 



Benzoic acid, C 6 H 5 CO 2 H, is benzene in which one hydrogen atom has been 



replaced by carboxyl, CO 2 H. 



Bitter almond oil, C 6 H 5 COH, is the aldehyde of benzoic acid, or benzoic acid 



from which one atom of oxygen has been 

 removed. 



Salicylic acid, C 6 H 4 .HO.CO 2 H, is benzene in which one hydrogen atom is re- 

 placed by hydroxyl and one by carboxyl. 



Gallic acid, C 6 H 2 .(HO) 3 .C0 2 H is benzene in which three hydrogen atoms are 



replaced by hydroxyl and one by carboxyl. 



rp . . , C 6 H,(HO)o.CO\ is formed from two molecules of gallic acid bv 



j.anmc acici, /~i TJ /Tj/~i\ c*d / ' i / TT V 



l - / 6 tl 2l- clv - 7 /3' l - yVj '/ removal of one molecule of water, or gallic 



acid in which the hydrogen of the hydroxyl 

 has been replaced by another gallic acid radical. 



Carbolic acid, Acidum carbolicum, C 6 H 5 HO = 94 (Phenol). 

 Crude carbolic acid is a liquid obtained during the distillation 

 of coal-tar between the temperatures of 170-190, and con- 

 taining chiefly phenol, besides kresylic acid, C 7 H 7 HO, and other 

 substances. It is a reddish-brown neutral liquid of a strongly 

 empyreumatic and disagreeable odor. 



By fractional distillation of the crude carbolic acid, the pure 

 acid is obtained, which forms colorless, interlaced, needle-shaped 

 crystals, sometimes acquiring a pinkish tint; it has a charac- 

 teristic, slightly aromatic odor, is deliquescent in moist air, 

 soluble in 20 parts of water, and very soluble in alcohol, ether, 

 chloroform, glycerine, fat and volatile oils, etc. ; it has. when 

 diluted, a sweetish and afterwards burning, caustic taste; it 

 produces a benumbing and caustic effect, and even blisters on 

 the skin; it is strongly poisonous, and a powerful antiseptic 

 agent, preventing fermentation and putrefaction to a marked 

 degree; fusing-point 42, boiling-point 182, specific gravity 

 1.065. 



Phenol, though generally called carbolic acid, has a neutral 

 reaction, and the constitution of an alcohol, but it readily com- 



