TJric Acid^ and their derivatives. 191 



If in the ureic residue of oxaluric acid we substitute hydro- 

 gen for hydroxyl, we get the formula for allanturic (lantanuric) 

 acid,C,H,N,0„ 



hLb 



U 



U 



and the mode in which this acid is produced from allantoine 

 by assimilation of water and separation of urea becomes evi- 

 dent if we give to allantoine, C.HgN^Og, the following form- 

 ula (2), viewing it as a di-ureide derivative of oxalic acid, 

 with which it appears in fact to be closely connected, producing 

 oxalates by heating with alkaline solutions, by fermentation 

 with yeast, &c. By reference to the formula proposed fur- 

 ther on for uric acid it will appear how this latter yields allan- 

 toine on boiling an aqueous solution with lead dioxide, the 

 middle carbon atom of the mesoxalic acid residue being re- 

 moved as carbon dioxide, and hydroxyl and hydrogen respect- 

 ively taken up from a molecule of water by the two ureic 

 residues, which at the same time assume a different mode of 

 attachment to the oxalic acid nucleus ; the further action of an 

 excess of lead dioxide decomposing the allantoine itself, with 

 formation of urea and lead oxalate. The formula of Gibbs for 

 allantoine (as for hydantoine and glycolurile) would lead us to 

 expect an acid character, whereas such compounds as are 

 formed by this body with metals and metallic oxides manifestly 

 are of the same order as those produced with similar substances 

 ty urea itself. In the other di-ureide, viz: mycomelic acid, 



Mycomelic acid (monobasic). 



A 



M 

 h i 



we have an example of what I agree with Professor Gibbs m 

 assuming as y^xj probable, namely, the similarity of function 



