408 EXCRETION 



It is without odor and of a cooling niter-like taste. It has neither an acid 

 nor an alkaline reaction, and deliquesces in a moist and warm atmosphere. 

 At 15 C. it requires for its solution less than its own weight of water. It is 

 soluble in all proportions of boiling water, and requires five times its weight 

 of cold alcohol for its solution. It is insoluble in ether. At 120 C. it melts, 

 and at a still higher temperature decomposes. 



Urea is decomposed by sodium hypochlorite or hypobromite or by nitrous 

 acid, with evolution of nitrogen. It forms compounds with acids, of which 

 the chief are urea hydrochloride, CON 2 H 4 .HCL; urea nitrate, CON 2 H 4 .- 

 HNO 3 ; and urea phosphate, CON 2 H 4 .H 3 PO 4 . It forms compounds with 



FIG. 293. Crystals of Urea Nitrate. FIG. 294. Crystals of Urea Oxalate. 



metals such as HgO.CON 2 H 4 , (or with silver, CON 2 H 2 Ag 2 ). Urea is iso- 

 meric with ammonium cyanate, NH 4 CNO, and was first prepared artificially 

 from that substance. 



The Formation of Urea. Proteins in the body have their nitrog- 

 enous moiety split off as ammonia, by what Folin considers essentially 

 a series of hydrolytic cleavages; this is then built up into urea, as described 

 more fully in the chapter on Metabolism. This last step is essentially a 

 synthetic process which, from the fact that ammonium carbonate introduced 

 into the blood is eliminated as urea, may be supposed to occur as follows: 



NH 2 NH 2 



/ / 



CO -H 2 =CO 



\ \ 



ONH 4 NH 2 



Ammonium Urea 



Carbamate 



Urea is present in varying amounts in all organs and fluids of the body, as 

 shown by the following determinations of Schoendorff on the dog: 



Organ Per urfa' f 



Blood 0.116 



Muscle o . 080 



Kidney 0.670 



Liver 0.112 



Heart 0.173 



Brain 0.128 



Spleen 0.122 



