334 BENZOIC ACID. 



A mixture of concentrated nitric and sulphuric 

 acids converts it into nitrosulphobenzoic acid, C 6 H 3 (^s&quot;0 2 ) 



I SO 2 OH we ^ developed crystals, easily soluble in 

 water which, when treated with ammonium hydro- 

 sulphide, is transformed into amidosulphobenzoic acid, 



C 6 H 3 (^N&quot;H 2 ) j gQ 2 QJT radiating, colorless needles. 



When distilled with phosphorus chloride, sulphoben- 

 zoic acid yields metachlorbenzoyl chloride. 



Parasulphobenzoicacid, C 7 IPS0 5 =C 6 IP 1 ^ OH 



Is formed in varying quantities, together with the 

 preceding compound, in the preparation of the latter; 

 and by oxidizing parasulphotoluene with potassium 

 bichromate and sulphuric acid. The free acid is very 

 similar to the meta-acid ; is not, however, deliquescent. 

 The add barium salt, (C 7 H 5 S0 5 ) 2 Ba + 3II 2 0, crystallizes 

 in long, flat needles, which are very difficultly soluble 

 in water. 



Disulphobenzoic acid, C 6 H 3 j , g( j 2 QJ Is formed 



by the action of concentrated sulphuric acid and phos 

 phoric anhydride on benzoic acid in sealed tubes. 

 Crystalline, deliquescent mass. The neutral barium 

 salt, (C 7 H 3 8 2 8 ) 2 Ba 3 + 7H 2 0, crystallizes in small, well- 

 formed prisms. 



Thiobenzoic acid, C 6 IP.CO.SH. Is obtained by 

 the action of benzoyl chloride on an alkaline solution 

 of potassium sulphite and precipitation with hydro 

 chloric acid. White, radiating, crystalline mass. Fus 

 ing point, 24. But slightly soluble in warm water. 

 Not distillable alone, but very easily with water va 

 por. In ethereal solution, in contact with the air, it 

 easily becomes oxidized, forming benzoyl disulphide 

 (C 6 IP.CO) 2 S 2 . 



A thiobenzoic acid, C 6 IP.CS.OH, isomeric with the 

 foregoing, is formed, together with benzoic acid, by the 



