76 Royal Society. 



the constitution of which, as far as my experiments go, may be re- 

 presented by the formula 



[C 7 (H J N J ')0][C,(H„H 2 N)0] 1 



There are not less than three other compounds known which em- 

 pirically may be represented by the same formula as amidobenzoic 

 acid, viz. nitrotoluol, salicylamide, and anthranilic acid. The two 

 former substances differ from amidobenzoic acid both physically and 

 chemically in a marked manner ; anthranilic acid, on the other hand, 

 is so closely allied to the benzoic derivative, that special experiments 

 were required to distinguish these two bodies. Gcrland, when he 

 submitted the two acids to Piria's well-known reaction, observed that 

 both are converted by nitrous acid into non-nitrogenated acids, which, 

 although still isomeric, essentially differ in their properties ; amido- 

 benzoic acid being transformed into a new acid, — oxybenzoic acid, 

 whilst anthranilic acid yields salicylic acid. 



It appeared of some interest to try whether the substitution of ni- 

 trogen for hydrogen in anthranilic acid would furnish a compound 

 isomeric with the double acid obtained from amidobenzoic acid. A 

 current of nitrous acid, when passed into a cold alcoholic solution of 

 anthranilic acid, rapidly transforms this substance into a compound 

 crystallizing in white prisms, which is easily obtained by allowing 

 the alcohol to evaporate at the common temperature. The new body 

 is extremely soluble in water, insoluble in ether. By analysis it was 

 proved to contain C H N O 



The new compound is thus seen to be far from isomeric with the 

 derivative of amidobenzoic acid produced under similar circumstances, 

 with which, in fact, it shows no analogy whatever. I have not yet 

 arrived at a definite view regarding the molecular construction of 

 this body ; nevertheless its deportment with water shows even now 

 that the nitrogen in it exists in two different forms. Gently heated 

 with water, the new compound disengages torrents of nitrogen ; on 

 cooling, the liquid solidifies into a crystalline mass of salicylic acid, 

 free nitric acid remaining in solution. This metamorphosis is repre- 

 sented by the equation 



C u H N 5 O 7 + 2H 2 O=N 4 + HNO 3 + 2C 7 H 6 O 3 , 



New body. Salicylic acid, 



which has been controlled by quantitative experiments. The idea 

 suggests itself to assume one-fifth of the nitrogen in the form of nitric 

 acid, when the new body might be viewed as a salt- like compound of 

 the formula 



the action of the water consisting simply in the replacement of the 

 monatomic nitrogen by the elements of water, which would produce 

 salicylic acid, nitric acid being liberated. 



I avail myself of this opportunity of mentioning the deportment of 



