BENZOIC ACID. 333 



by boiling with water, yielding nitrogen, nitric acid, 

 and meta-oxybeiizoic acid. Explodes violently when 

 heated. 



Diazobenzoic-Amidobenzoic acid, C 7 H 4 N 2 2 -f 

 C 7 II 5 (OTi 2 )0 2 . Is produced by mixing aqueous solu- 

 tions of nitric-diazobenzoic acid and meta-amidobenzoic 

 acid. Can be prepared most readily by conducting 

 nitrous acid into an alcoholic solution of meta-amido- 

 benzoic acid, or by mixing this solution at 30 with 

 ethyl nitrite, the acid in this case being thrown down 

 immediately. Orange-yellow crystalline granules, or 

 small microscopical prisms. Inodorous and tasteless. 

 Almost insoluble in water, alcohol, and ether. Is de- 

 composed at 180, the decomposition being accom- 

 panied by a detonation. "Weak, bibasic acid. The 

 salts are easily decomposed in aqueous solution, nitro- 

 gen being evolved. Heated with hydrochloric acid 

 the acid is decomposed below 100, yielding chlorben- 

 zoic acid and meta-amidobenzoic acid hydrochlorate. 

 Hydrobromic and hydriodic acids cause an analogous 

 decomposition. 



Para-amidobenzoic acid conducts itself like meta- 

 amidobenzoic acid when treated with nitrous acid, and 

 yields diazo-compounds, which are isomeric with those 

 just described, and completely analogous to them. 



Meta-sulphobenzoic acid, C 7 H 6 S0 5 = 

 C 6 H 4 j gQ2Qjj Is formed, together with a small 



quantity of the para-acid, by the action of fuming 

 sulphuric acid on benzoic acid, and when the vapor of 

 sulphuric anhydride is conducted upon dry benzoic 

 acid. Separated from the barium salt, it forms a crys- 

 talline, colorless, very deliquescent, strongly acid mass. 

 Very stable bibasic acid. The neutral barium salt, 

 C 7 H 4 S0 5 Ba, is very easily soluble; the acid salt, 

 (C 7 IPS0 5 ) 2 Ba + 3IPO, crystallizes in difficultly soluble, 

 oblique rhombic prisms. 



