285 



action of heat upon urea (cyanuric acid), and described by him as 

 biuret ; the second is the guanidine of M. Strecker. A glance at 



their formulae, 



Cyanuric acid .... C 3 H 3 N 3 O 3 , 



Biuret C 2 H 5 N 3 2 , 



Guanidine C H 7 N 3 O, 



shows that these substances are similarly related to each other as the 

 derivatives of cyanuric ether, and appropriately selected methods 

 will not fail to arrest the reaction at the intermediate stages. 



Even now the cyanogen group is particularly rich in examples of 

 serial transformations, accomplished under the influence of success- 

 ively assimilated water-molecules. Liebig's celebrated researches 

 have shown that melamine before it is converted into cyanuric acid 

 undergoes a series of changes. Fixing water and losing ammonia 

 in the same proportion, melamine is successively converted into am- 

 melide, ammeline, and cyanuric acid. The latter, fixing water and 

 losing carbonic acid instead of ammonia, passes through the inter- 

 mediate stages, which I have endeavoured to trace, and is ultimately 

 resolved into carbonic acid and ammonia. 

 The equation 



C 3 H 6 N 6 + 6H 3 O = 6H 3 N + 3CO 2 



Melamine. Water. Ammonia. Carbonic acid, 

 represents the final result of the decomposition of melamine under 

 the influence of the hydrated alkalies, but the water which figures in 

 this equation is fixed, molecule after molecule, and the ultimate pro- 

 ducts are preceded by not less than five intermediate compounds, the 

 successive formation and decomposition of which is illustrated by the 

 following series of symmetrical equations : 

 Melamine . . . C 3 H 6 N 6 + H 2 O= H 3 N + C 3 H 5 N 5 O Ammelide. 

 Ammelide . . C 3 H 5 N 5 O + H 2 O= H 3 N + C 3 H 4 N 4 O a Ammeline. 

 Ammeline . . C 3 H 4 N 4 O 2 + H 2 O = H 3 N + C 3 H 3 N 3 O 3 Cyanuric acid . 



Cyanuric acid C 3 H 3 N 3 O 3 -f H 2 O = C O 2 -f C 2 H 5 N 3 2 Biuret. 



Biuret C 2 H 5 N 3 O 2 -f H 2 O = C O 2 + C H 7 N 3 O Guanidine. 



Guanidine . . C H 7 N 3 O + H 2 O = C O 2 -f H 9 N 3 Ammonia. 



In carrying out the experiments, which form the subject of this 

 Note, I have been most ably assisted by Dr. C. A. Martius, to whom 

 my best thanks are due for his zealous and skilful co-operation. 



VOL. XI. X 



