60 ORGANIC CONSTITUENTS. 



the blue colour disappears : dilute sulphuric acid is then to be 

 added in excess. It falls in crystalline scales of a silky lustre ; 

 is insoluble in water and dilute acids, but is taken up by 

 ammonia and the fixed alkalies. 



If a solution of miu'exan in ammonia be exposed to the air, 

 it acquires a purple-red colour and deposits crystals of murexid : 

 with an excess of ammonia it again becomes colourless, and is 

 then found to contain oxalurate of ammonia. 



Its formula, according to Liebig and Wohler, is C^ H^ N„ O^; 

 according to Fritzsclie it is Cjg H^ N^ Oj^. 



The substances Avhich have been described are only a few of 

 the products of nitric acid on uric acid ; they have been selected 

 as having a more practical bearing than the others. The fol- 

 lowing table exhibits the principal results of Liebig and Wohler^s 

 admirable paper on this subject. 



(a) On treating uric acid with cold concentrated nitric acid, 

 we obtain alloxan, C^ H^ N^ O,,^ or 2 01 + 0,+ 4 HO. 



{b) On treating uric acid with cold dilute nitric acid, we obtain 

 alloxantin, C^ H^ N„ O,^, or 2U1 +0+ 5 HO. 



(c) On treating alloxan with sulphurous acid, we obtain thion- 



uric acid, C^ H^ Ng O^^ S„. 



(d) On treating thionuric acid, or thionurate of ammonia, with 



hydrochloric, or sulphuric acid, we obtain uraniil, 

 C, H^ N3 O,, or 2UI + NH3 + 2HO. 



(e) On treating alloxan with sulphuretted hydi'ogen, we ob- 



tain first, alloxantin, and subsequently dialuric acid, 

 C3H^N„0,, or 2UI + 4HO. 



(/) On warming uric acid in eight parts of nitric acid we ob- 

 tain |j«ra6a«ic acid, Cg N^ 0^ + 2H0. 



[ij) On boiling parabanic acid in ammonia, oxalurate of ammo- 

 nia is generated, from which we can obtain oxaluric 

 acid, C, N^ Hg O, + HO. 



(A) On the addition of an alkali to a concentrated solution of 

 alloxan, we obtain alloxanic acid, C^ H, N^ 0^ + 2 HO. 



[i) By the precipitation of a solution of alloxan Avitli boiling 

 acetate of lead, we obtain mesoxalic acid, C O . 



{j) By heating a solution of alloxan with ammonia, we obtain 

 mycomelinic acid, C^ H N^ O . 



{k) On heating uramil with dilute sulpluu-ic acid, we obtain 

 uramilic acid, C,,. H,, N O, . 



