94 ANIMAL CHEMISTRY LECTURE IV. 



Hitherto the transformation of fatty into aromatic compounds 

 has not been accomplished according to any definite reaction; 

 but both phenene C6H6, and phenol or carbolic acid CeH^O, are 

 producible by transmitting the vapour of alcohol or fousel oil 

 through red-hot tubes. From the former of these bodies we 

 readily obtain aniline or phenylamine CgH-rN, which is recon- 

 vertible into both phenene and phenol. 



(100.) The 7-carbon fatty acid and alcohol are usually ob- 

 tained from castor oil. So far as I know, they have not yet been 

 produced artificially from inorganic materials, but undoubtedly 

 could be so produced at any moment. With the 7-carbon 

 aromatic compounds the case is different. By the general pro- 

 cesses already referred to, phenene has been converted into 

 benzoic acid C 7 H6O 2 , by Harnitzky and Kekule, and phenol into 

 salicic acid C 7 H6O 3 , by Kolbe. Benzoic acid readily yields 

 benzoic aldehyd or essential oil of bitter almonds, and also glyco- 

 benzoic or hippuric acid. Salicic acid, again, is readily oxidi- 

 sable into gallic acid, of which tannin constitutes the natural 

 glucoside, as shown by the following decomposition : 



Tannin Water Glucose Gallic acid 



C, 7 H W I7 + 4 H a O = C 6 H X ,0 6 + 



From salicic acid we may also obtain methyl-salicate or essential 

 oil of wintergreen, salicic aldehyd or essential oil of spirasa, and 

 saligenin or salicylic alcohol, a compound frequently mentioned 

 in my second lecture as a constituent residue of salicin and 

 populin salicin being, indeed, a glucoside of saligenin, much 

 in the same way that tannin is a glucoside of gallic acid, thus : 



Salicin Water Glucose Saligenin 



C I3 H I8 7 + H a O = C 6 H Ja 6 + C 7 HA 



Moreover, tyrosine a very remarkable product of tissue 

 metamorphosis though not yet produced from salicic acid, has 

 much the same relation thereto that leucine has to caproic, and 



