288 URINE. [CH. xn. 



Nitrous acid decomposes urea as follows : 

 CO(NH 2 ) 2 + 2HNO 2 = 2N 2 + CO 2 + sH 2 O. 



Hypobromites effect a similar decomposition. 

 CO(NH 2 ) 2 + 3 NaBrO = sNaBr + CO 2 + N 2 + 2 H 2 O 



Sodium 

 hypobromite. 



According to Werner* the reactions of urea are better 

 understood if it be supposed that it exists in two tauto- 

 meric modifications, the equilibrium between them 

 depending on the reaction 



/OH 



HN = C^ HN = C' x 



\NH 2 NH 3 



A. B. 



The A form exists in strongly acid solutions. It is 

 decomposed by nitrous acid, like all compounds with the 

 NH 2 group. The B form exists in neutral or alkaline 

 solutions and is not decomposed by nitrous acid. >For the 

 convincing evidence on which this view is based the 

 original papers should be consulted. 



333. To a watch-glass half full of distilled water add as much 

 solid urea as will lie on a sixpenny-piece. Note the solubility of urea 

 in water. 



334. Place a drop of the urea solution on a slide, add a single 

 drop of a saturated solution of oxalic acid, mix by stirring with a 

 needle or fine glass rod, cover with a slip and examine the crystals 

 of oxalate of urea that separate out. They vary considerably, 

 containing long, thin, flat crystals, often in bundles and rhombic 

 prisms. Draw the crystals. 



* Journal Chem. Soc. y cix.,,p. 1120. 



