1008 CYANOGEN COMPOUNDS. 



is deposited in crystals, which are purified by new crystalliza- 

 tions. 2. From alloxan. It is produced in large quantity by 

 carrying a stream of sulphuretted hydrogen into a solution of 

 alloxan. Sulphur is first deposited, and then the whole 

 becomes a thick mass of crystals of alloxantin, which are 

 separated from sulphur by solution in boiling water. The 

 alloxantin crystallizes by evaporation in a state of purity. 

 3. On exposing a solution of alloxan to the action of the voltaic 

 battery, oxygen is evolved at the zincoid, and alloxantin is de- 

 posited on the chloroid in crystalline crusts. 



Alloxantin crystallizes in oblique prisms of four sides, which 

 are colourless or slightly yellow, hard and easily reduced to 

 powder ; they become red in air impregnated with ammonia and 

 acquire a green metallic lustre. They are not altered at 

 212, but at 302 (150 centig.) lose three atoms of water; are 

 sparingly soluble in cold water, more soluble in boiling water ; 

 the solution reddens litmus. Alloxantin heated in chlorine- 

 water, or in strong nitric acid, is changed into alloxan ; with 

 salts of silver, it produces a black precipitate of metallic 

 silver. It is decomposed by alkalies ; barytes-water produces 

 in its solution a violet precipitate, which is made colourless by 

 heat, and in the end disappears entirely. By the action of 

 boiling sulphuric acid, 2 atoms of alloxan are converted, with 

 the concurrence of 2 atoms of water, into.l atom of alloxantin, 

 3 atoms of oxalic acid, 2 atoms of ammonia, and 2 atoms of 

 carbonic acid. 



The circumstances of the formation of alloxantin are thus 

 explained by M. Liebig. By the action of nitric acid, the urile 

 of the uric acid combines with 1 atom of oxygen and with the 

 elements of 5 atoms of water, giving rise to 1 atom of allox- 

 antin and to peroxide of nitrogen, NO 4 , which in contact with 

 water is converted into nitrous and nitric acids ; the nitrous 

 acid is decomposed with half of the urea set at liberty, while 

 the other half of the urea forms with nitric acid, nitrate of urea. 

 In the process again with sulphuretted hydrogen, 1 atom of 

 oxygen of the alloxan combines with hydrogen from the sulphu- 

 retted hydrogen to form water which remains in the constitution 

 of the alloxantin ; the sulphur set free is deposited. 



Products of the decomposition of alloxantin. When a stream 

 of sulphuretted hydrogen is carried into a boiling solution of 



