PHTALIC ACID. 363 



with an excess of potassa or lime, it breaks up into 

 benzene and carbonic acid ; when 1 molecule of its 

 calcium salt is heated with 1 molecule calcium 

 hydroxide at 330-350, calcium benzoate is the result. 

 When heated with hydriodic acid, it undergoes the 

 same change. With phosphorus chloride it yields 

 phtalyl chloride C 6 H 4 (CO.C1) 2 , a light-yellow liquid, boil- 

 ing at 270. 



Barium phtalate, C 8 H 4 4 Ba, forms small laminae, 

 which are very difficultly soluble in water. 



Methyl and ethyl phtalate are colorless liquids. 



Dichlorphtalic acid, C 6 H 2 C1 2 (CO.OH) 2 , is prepared 

 by boiling dichlornaphthalene tetrachloride (which see) 

 with ordinary nitric acid. Slightly yellowish colored, 

 thick, intertangled prisms ; fusing point, 183-185 ; 

 easily soluble in ether, alcohol, and hot water. 



Tetrachlorphtalic acid, C 6 C1 4 (CO.OH) 2 , is obtained 

 by heating pentachlornaphthalene with dilute nitric 

 acid to 180-200. Colorless laminae, or hard, thick 

 plates; fuses at 250, at the same time breaking up 

 into water and anhydride. 



Monobromphtalic acid, C 6 H 3 Br(CO.OH) 2 . By 

 heating phtalic acid, for a long time, with an excess of 

 bromine and water at 180-200. White, crystalline 

 powder; fusing point, 136-138; easily soluble in 

 water, alcohol, and ether. 



Nitrophtalic acid, C 6 H 3 (^0 2 )(CO.OH) 2 . By digest, 

 ing phtalic acid with nitric-sulphuric acid. Pale yel- 

 low prisms ; fusing point, 208-210 ; easily soluble in 

 water, alcohol, and ether. When heated with tin and 

 hydrochloric acid it is converted into ineta-amidoben- 

 zoic acid, carbonic anhydride being given off. 



Hydro phtalic acid, C 8 H 8 4 . Is produced by con- 

 tinued action of sodium-amalgam on a cold solution ot 



