MELLITIC ACID. 371 



Paramide (Mellimide), C 12 H 3 ^ 3 6 = C 6 (g | KEl) * 



Ammonium mellitate, when heated to 160, is re- 

 solved into water, ammonia, paramide, and ammo- 

 nium euchronate. Paramide, which is insoluble in 

 water, can be freed of the euchronate by water. 

 White, amorphous mass, insoluble in water and alco- 

 hol ; is converted into acid ammonium mellitate when 

 heated with water to 200. 



Euchronic acid, C 12 m$T 2 8 = 



C 6 (JQ 1 NH V(CO.OH) 2 . Is separated from its ammo- 

 nium salt (see above, Paramide) by means of hydro- 

 chloric acid. Colorless, short prisms ; but slightly 

 soluble in cold water; heated with water to 200, it is 

 converted into acid ammonium mellitate. Its solution, 

 when brought in contact with zinc or nascent hydro- 

 gen from any. source, throws down a deep-blue, insolu- 

 ble body, euchron, which, when gently heated in the 

 air, is reconverted into colorless euchronic acid, and 

 dissolves in alkalies, forming beautiful, purple-red 

 solutions, which rapidly become colorless in contact 

 with air. 



Hydromellitic acid, C 12 H 12 12 . Is formed slowly 

 by the action of sodium amalgam on ammonium melli- 

 tate. Colorless, indistinct crystals ; easily soluble in 

 water ; hexabasic. When kept it is slowly converted 

 into isohydromellitic acid, C 12 H 12 12 ; the same change 

 takes place rapidly when it is heated with concentrated 

 hydrochloric acid to 180. Isohydromellitic acid crys- 

 tallizes in thick, four-sided prisms, is easily soluble in 

 water, and is precipitated from the aqueous solution 

 by hydrochloric acid. By heating hydromellitic acid 

 with concentrated sulphuric acid, there is formed, 

 under certain conditions, a third isomeric acid, meso- 

 hydromellitic acid, which forms voluminous needles, 

 very difficultly soluble in cold water. 



