118 ANIMAL OXIDES WITH AZOTE NOT OILY. 



beautiful cantharides green crystals constituting the purpurate of 

 ammonia of Prout. But we do not obtain them, if we conti- 

 nue the heat beyond a certain time; the solution even loses 

 the property of becoming coloured with ammonia. The reason 

 of these phenomena is obvious : the solution of alloxantin treat- 

 ed with a certain quantity of nitric acid and ammonia furnishes 

 the green crystals. But when all the alloxantin is converted 

 into alloxane by the action of the nitric acid, these crystals cease 

 to make their appearance. 



Nitrate of silver converts alloxantin into alloxane, by giving 

 out an atom of oxygen, which forms water with the additional 

 atom of hydrogen, while the silver is precipitated in the metal- 

 lic state. 



SECTION VI. OF URAMILE. 



Pure uramile* is obtained by boiling for some minutes a mix- 

 ture of thionuric acid or thionurate of ammonia, and dilute sul- 

 phuric or muriatic acid. The solution, even though dilute, con- 

 cretes at that temperature into a white magma consisting of very 

 minute brilliant needles. This magma is easily washed, and di- 

 minishes enormously in volume when dried. 



Uramile may be prepared exceedingly beautiful by dissolving 

 thionurate of ammonia in cold water, heating the solution to the 

 boiling point, adding the requisite quantity of muriatic acid, 

 keeping the mixture boiling for a few minutes, and then allowing 

 it to cool. In this case the uramile is formed slowly, and crys- 

 tallizes in long brilliant hard needles, having a feathery form. 



Dr Gregory of Aberdeen has given the following process for 

 preparing uramile : Dissolve thionurate of ammonia in boiling 

 water, add a small excess of dilute sulphuric acid, and boil for a 

 short time. Even while hot uramile is deposited in large quan- 

 tity. It is to be collected and dried by pressure. 



Dry uramile is white, has a satiny lustre, is insoluble in cold 

 water ; but slightly soluble in boiling water, from which it sepa- 

 rates as the liquid cools. It dissolves in ammonia and is thrown 

 down unaltered by the addition of acids to the solution. When 

 boiled with ammonia it is decomposed ; the liquid becomes yel- 

 lowish, and acquires the property of assuming a deep purple co- 

 lour and of depositing green crystalline needles. Uramile con- 



* Ann. de Chim et de Phys. Ixviii. 261. 



