TOLUIC ACIDS. 339 



dies ; fusing point, 90-93. Chromic acid oxidizes it, 

 forming isophtalic acid. 



Calcium meta-toluate, (C'H 7 2 ) 2 Ca + 2H 2 0. Nee- 

 dies, easily soluble in water. 



Brommeta-toluic acid, C 6 H 3 Br Is formed 



together with the isomeric compound, brompara-toluic 

 acid, when the mixture of brommeta- and brompara- 

 xylene, obtained by the action of bromine on xylene 

 from coal-tar, is boiled for a long time with potassium 

 bichromate and dilute sulphuric acid. By preparing 

 the barium salt, which is comparatively difficultly solu- 

 ble in water, it can be readily separated from the para- 

 acid. Crystalline powder, difficultly soluble even in 

 boiling water. Fusing point, 205-206. 



3. Para-toluic acid. Is produced from parabrom- 

 toluene by the simultaneous action of sodium and car- 

 bonic acid ; from para-xylene or cyrnene by boiling for 

 several days with dilute nitric acid (mixture of 1 vol- 

 ume nitric acid .of specific gravity, 1.4 with 2-3 vol- 

 umes water), in a flask connected with a reversed con- 

 densing apparatus. The acid, that separates on cool- 

 ing, still contains impurities in the form of nitro-sub- 

 stitution-products. In order to free it from these, it is 

 suspended in water and this distilled, the acid passing 

 over with the vapors ; or the crude acid is heated for 

 some time with tin and concentrated hydrochloric acid, 

 and the undissolved portion crystallized from boiling 

 water. Fine, colorless, needly crystals. But slightly 

 soluble in cold water, comparatively easily in boiling 

 water, but less so than benzoic acid, very readily solu- 

 ble in alcohol. Fuses at 176, and sublimes easily. 

 Chromic acid oxidizes it, forming terephtalic acid. 



Calcium para-toluate, (C 8 H 7 2 ) 2 Ca + 3H 2 0, crystal- 

 lizes in lustrous, colorless needles, that are easily soluble 

 in water. 



