206 CONJUGATED ACIDS. 



readily in hot water ; it is insoluble in alcohol ; with the alkalies it 

 forms acid and neutral salts ; this acid may be regarded as a com- 

 bination of the above mentioned hypothetical urilic acid with water; 

 3 atoms of urilic acid and 1 atoms of water forming 2 atoms of 

 hydrurilic acid. By nitric acid, this acid is converted into nitro- 

 hydrurilic acid, C 8 H 2 N 3 O 14 . 



Oxaluric acid. C fi HoN O 7 .HO : if a solution of uric acid in 



> O O ^ / 



dilute nitric acid be supersaturated with ammonia and evaporated, 

 the ammonia-salt of this acid separates in needles ; on separating the 

 acid from the salt by means of a more powerful acid we obtain it 

 as a glistening white crystalline powder with an acid taste ,and an 

 acid reaction ; when heated it becomes decomposed into 2 atoms 

 of oxalic acid and 1 atom of urea, for C 6 H 3 N 2 O 7 .HO==2C 2 O 3 + 

 C 2 H 4 N 2 O 2 . 



Crystallised oxaluric acid may therefore be regarded as a 

 combination of 2 atoms of oxalic acid and 1 atom of urea, for 

 C 4 6 +C 2 H 4 N 2 2 =C 6 H 4 N 2 8 . 



Parabanic acid when boiled with ammonia takes up 3 atoms of 

 water, and forms oxaluric acid, for C 6 N 2 O 4 + H 3 O 3 = C 6 H 3 N 2 O 7 . 



Thionuric acid^ C 8 H 7 N 3 S 2 O 14 , is formed by mixing a solution 

 of alloxan with an excess of aqueous sulphurous acid, supersa- 

 turating with ammonia and boiling for some time ; as the solution 

 cools, thionurate of ammonia separates in nacreous crystalline 

 scales ; on combining the acid of this salt with lead, decom- 

 posing the lead-salt by sulphuretted hydrogen, and evaporating 

 the filtered fluid, we obtain thionuric acid in the form of a white 

 crystalline mass with an acid taste, which is unaffected by exposure 

 to the air, dissolves readily in water, and is decomposed both by 

 simple boiling and on the addition of acids. The salts of this acid 

 saturate 2 atoms of base ; on the addition of concentrated sulphuric 

 acid, sulphurous acid is developed. 



Thionuric acid may be regarded as a combination of 1 atom of 

 alloxan with 1 atom of ammonia and 2 atoms of sulphurous acid, 

 for C 8 H 4 N 2 10 + H 3 N+ S ? O 4 =C 8 H 7 N 3 S 2 O I4 . 



Uramile, C 8 H 5 N 3 O 6 , is produced either by simply exposing 

 thionuric acid to ebullition, or by treating thionurate of ammonia 

 with an excess of hydrochloric acid; it forms minute, silky, glis- 

 tening needles, and on exposure to the atmosphere and to warmth, 

 assumes a rose-red tint. It is insoluble in cold water and only 

 dissolves slightly in boiling water ; the caustic alkalies and concen- 

 trated sulphuric acid dissolve, but do not decompose it : by simple 

 ebullition, however, its solutions become decomposed. The alkaline 



