TheMellitates — Euchronic Acid. 4*3 



H« O, O O) - (N 2 H 6 + H 8 O) m O H 2 N 2 O. How- 

 ever, the process is not simple, on account of the simulta- 

 neous formation of euchronic acid. By boiling with water 

 paramid takes up 2 atoms and forms 1 atom ammonia and 

 2 atoms of mellitic acid, C s H 2 N 2 O + H* O 2 = 2 O O 3 

 + N 2 H^ 



The metamorphosis takes place best at 200°; at 100° eu- 

 chronate of ammonia is formed, and at this temperature remains 

 unchanged. Paramid is soluble in alkalies, and when heated 

 with them becomes voluminous, and is dissolved on addition 

 of water. If hydrochloric acid be instantly added, unchanged 

 paramid is precipitated ; if, however, it be allowed to stand, 

 ammonia is evolved, and the solution then contains at first 

 euchronic acid, and at a later period mellitic acid. This 

 change takes place instantly on the application of heat. By 

 dissolving paramid in ammonia and instantly precipitating by 

 nitrate of silver, a compound of paramid with oxide of silver 

 was obtained, which did not lose water at 150°; this shows 

 that paramid does not contain water, and cannot therefore be 

 O N 2 O 3 + H 8 O. 



Euchronic Acid. — That part of the product obtained by heat- 

 ing mellitate of ammonia, which is soluble in water, is acid eu- 

 chronate of ammonia; if the decomposition be not completed 

 it contains acid mellitate ; if the temperature is too high it 

 is yellow, and contains the yellow bitter matter. It is de- 

 posited in white scarcely crystalline crusts, reacts strongly 

 acid, is not very soluble in cold water, and the paramid must 

 therefore be edulcorated for a long time. To obtain the acid, 

 the salt is dissolved in the smallest possible quantity of hot 

 water, and the hot solution treated with nitric or hydrochloric 

 acid ; on cooling the acid separates as a white crystalline pow- 

 der. It may be purified by re-solution in boiling water, and 

 may be obtained in small crystals. It is very strongly acid, 

 tastes like bitartrate of potassa. The crystals lose water when 

 heated, and become opake. If crystallized from a solution 

 containing sal-ammoniac, it often contains a trace of ammonia, 

 and is then of a yellowish colour. It loses 2 atoms of water 

 at 200°. Can be heated to 280° without change ; further 

 heated is decomposed, and gives cyanide of ammonium and a 

 deep green bitter sublimate. Heated with but very little 

 water to 200° in a closed tube it is dissolved, and in the 

 solution is found acid mellitate of ammonia. If a piece of 

 metallic zinc be put into a solution of euchronic acid, it be- 

 comes instantly covered with a layer of a splendid blue colour ; 

 if the plate of metal be dipped into dilute hydrochloric acid, 

 the blue deposit is separated, and may be washed and dried. 



