936 ACIDS DERIVED FROM CARBONIC OXIDE. 



tions. Neutral mellitate of ammonia undergoes a remarkable 

 decomposition by heat, which has been lately investigated by 

 Woehler. Heated for some time between 302 and 320, it 

 loses ammonia, and is transformed into a pale yellow powder, 

 which water decomposes into two substances, one of which, 

 paramide, is white and insoluble, and the other a soluble am- 

 moniacal salt, of which the acid is named euchronic (from 

 tvxpoos, of a fine colour). The composition of paramide is 

 C 8 HNO 4 ; it appears to be formed from 2 atoms of mellitate of 

 ammonia, C 8 H 8 N 2 O 8 , by the loss of 1 atom of ammonia and 

 4 atoms of water. By boiling with water, particularly under 

 pressure at 392 (200 centig.), it is converted into acid mellitate 

 of ammonia. 



Euchronic acid, 2HO,C 12 NO 6 + 2HO, is separated from the 

 above acid ammoniacal salt by nitric or hydrochloric acid. It 

 crystallizes in very small, colourless, rhomboidal prisms, which 

 have a strong acid taste, and dissolve with difficulty ; they lose 

 2HO at 392. It fuses and is decomposed above 536. When 

 crystallized euchronic acid is heated to 392, in a glass tube 

 hermetically sealed, with a quantity of water insufficient to dis- 

 solve it, a complete solution is obtained, in which, however, the 

 euchronic acid is converted into acid mellitate of ammonia. 

 Euchronic acid is distinguished from all other organic com- 

 pounds by the way in which it comports itself with metallic 

 zinc. A slip of zinc dipt in a solution of this acid, immediately 

 becomes of a magnificent blue colour at its surface ; this colour 

 becomes at the boiling point nearly as intense as that of indigo. 

 Washed and dried, it forms a black mass which contains no 

 zinc. When slightly heated, even upon paper, it becomes im- 

 mediately completely white, and is changed anew into euchronic 

 acid. M. Wcehler applies the name euchroneto the blue compound, 

 and considers that the action of zinc in its formation is a deox- 

 idating one, euchrone being an inferior degree of oxidation of 

 the radical of euchronic acid, or that radical itself ; but from 

 want of material this singular and most interesting body was 

 not fully investigated. (Ann. de Chim. &c. 3 ser. ii, 78). 



Mellitate of silver undergoes a particular decomposition at 

 356, losing an atom of water, and becoming Ag,C 4 O 4 . 



Mellitate of alumina, native mellite or honeystone is com- 

 posed of A1 2 O 3 ,3C 4 O 4 H-H8HO, according to Wcehler. It 



