CONSTITUTION OF HIPPURIC ACID. 37 



a. Benzole acid C 7 H 6 O a 



/3. Oxiacetic acid C,H 4 3 



7. Ammonia H 3 N 



C 9 H I3 N0 5 

 - i. Water H 4 0, 



Hippuric acid C^Hg N0 3 



(36.) You observe that by subtracting two atoms of water from 

 the sum of the atoms of carbon, hydrogen, nitrogen, and oxygen 

 contained in the three molecules of benzoic acid, oxiacetic acid, 

 and ammonia, there is left a compound having the formula of 

 hippuric acid. Now there are few bodies about whose intimate 

 constitution greater varieties of opinion have been maintained than 

 with regard to this acid. Each successive chemist who has sub- 

 mitted it to examination has acted upon it with a different reagent, 

 and accordingly as the special reagent employed has attacked one or 

 other of the different residues entering into its constitution, so has 

 a different hypothetical formula been accorded to the unfortunate 

 body. Of the three constituent residues, the oxiacetic is the 

 most easily oxidisable, and accordingly when hippuric acid is 

 acted upon by oxidising agents, peroxide of lead for instance, the 

 acetic residue is destroyed, while the benzoic and ammonia residues 

 remain combined with one another in the form of benz amide. 

 Hence hippuric acid was represented as a compound of some form 

 of acetic acid with benzamide, which is. itself resolvable into ben- 

 zoic acid and ammonia. (Fehling.) 



o. Benzoic acid 

 7, Ammonia 



- Water H a O 



Benzamide C 7 H 7 NO 



(37.) Ammonia undergoes a very remarkable decomposition 

 when acted upon by nitrous acid, its hydrogen being transformed 



