56 ANIMAL ACIDS CONTAINING AZOTE. 



When thionurate of ammonia is mixed with nitrate of silver, 

 the oxide is reduced to the metallic state, and the silver is depo- 

 sited on the inside of the tube, giving it the appearance of a mir- 

 ror. 



Thionurate of barytes, recently precipitated, even from a di- 

 lute solution, has the form of a gelatinous mass, which gradually 

 becomes opaque and crystalline. When boiled with nitric acid, 

 this salt gives sulphate of barytes, and no sulphuric acid remains 

 free. This shows that the salt is a compound of one atom thio- 

 nurie acid and two atoms barytes. 



The formation of thionuric acid from alloxane and sulphurous 

 acid is easily explained. 



1 atom alloxane is . C 8 H 4 Az 2 O 10 



1 atom ammonia, , , H 3 Az 



2 atoms sulphurous acid," ... O 4 S 2 



Making altogether, . C 8 H 7 Az 3 O 14 S 2 



1 atom thionuric acid, ;^ C 8 H 5 Az 3 O 12 S 2 



2 atoms water, . . H 2 O 2 



Making together, . C 8 H 7 Az 3 O 14 S 2 



From this we see that two atoms sulphurous acid and one atom 

 f ammonia unite with one atom of allophane, and the product 

 is one atom of thionuric acid and two atoms of water. 



Wohler and Liebig seem to be of opinion that the sulphurous 

 acid in thionuric acid is converted into sulphuric acid. But there 

 seems no evidence for this. We see only that the elements of 

 two atoms sulphurous acid and one atom ammonia unite with an 

 atom of alloxane, and form thionuric acid. If it existed in the 

 state of sulphuric acid, barytes surely would be able to detect its 

 presence. But we have seen that this is not the case. 



SECTION X. OF URAMILIC ACID. 



This acid also was discovered by Wohler and Liebig during 

 their important investigation of uric acid and its products in 

 1838.* 



It may be obtained by mixing a cold solution of thionurate of 

 ammonia with a small quantity of sulphuric acid, and evaporating 

 the mixture in a gentle heat. The uramile separates by little 



* Ann. de Chim. et cte Phys. lxviii.308. 

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