URIC ACID. 207 



solution of uramile on exposure to the air assumes a purple red 

 tint, and deposits green crystals with a metallic lustre. 



On simply boiling thionuric acid, 2 atoms of sulphuric acid are 

 ghen off, and uramile is formed; for C 8 H 7 N 3 S 2 O 14 -2SO 3 .HO=: 

 C 8 H 5 N 3 6 . 



Uramile may be regarded as uric acid in which the urea is re- 

 placed by 1 atom of ammonia and 2 atoms of water ; it is, therefore, 

 hypothetically composed of 1 atom of urilic acid, 1 atom of ammonia, 

 and 2 atoms of water, for C 8 N 2 O 4 + H 3 N + 2HO = C 8 H 5 N 3 O 6 . 



Uramilic acid, C 16 H 10 N 5 O 15 , is formed by boiling uramile either 

 with a solution of potash or with dilute acids ; it crystallises in 

 colourless, four-sided prisms, or silky, glistening needles, is soluble 

 in water, faintly reddens litmus, dissolves without the development 

 of gas, or the communication of colour, in sulphuric acid; is decom- 

 posed by nitric acid, and forms soluble salts only with the alkalies. 



Acids and alkalies expel 1 atom of ammonia from 2 atoms of 

 uramile, which, in its place, receive 3 atoms of water ; C 16 H 10 N 6 O 12 

 -H 3 N + 3HO=C I6 H 10 N 5 15 . 



Alloxantin, C 8 H 5 N 2 O 10 , is formed by boiling 1 part of uric acid 

 with 32 parts of water, then gradually adding dilute nitric acid, and 

 finally evaporating the fluid to one third of its volume: after some 

 time crystals of alloxantin separate themselves. It is prepared 

 from alloxan by the action of reducing bodies, as for instance, sul- 

 phuretted hydrogen, or hydrochloric acid and zinc. It crystallises 

 in oblique four-sided prisms, which at first are colourless, but on 

 exposure to the air become yellowish, and if acted on by the 

 vapour of ammonia, become red. It is slightly soluble in cold, but 

 dissolves readily in hot water, it reddens litmus, and is converted 

 by chlorine into alloxan ; with baryta-water it gives a violet- 

 coloured precipitate. 



When very dilute nitric acid acts on uric acid, the urilic acid 

 takes up 1 atom of oxygen from the nitric acid and 5 atoms of 

 water in order to form alloxantin (C 8 N 2 O 4 -f O -f 5HO= 

 C 8 H 5 N 2 O 10 ), while the hyponitric acid which is formed, becoming 

 decomposed into nitrous and nitric acids, partly combines with and 

 partly decomposes the urea of the uric acid. 



On treating alloxan with sulphuretted hydrogen, the sulphur 

 separates, while the hydrogen unites with the alloxan, and forms 

 alloxantin, C 8 H 4 N 2 O 10 + H = C 8 H 5 N 2 O 10 . 



Mureocide,C ie2 R^) s ,purpurate of ammonia, may be obtained 

 by several very different methods. The most simple means of 

 preparing it is by boiling equal parts of uramile and red oxide of 



