UREA. 227 



needles. The free acid, separated from this salt by 

 means of hydrochloric acid, is solid, easily soluble in 

 water, alcohol, and ether. Exceedingly unstable. 



{TS^TT P2TT5 

 g'' The 



crystalline ethylamine salt (fusing point, 103) of this 

 acid is formed by adding carbon bisulphide to an alcoho- 

 lic solution of ethylamine. It is easily soluble in water. 

 From its solution metallic salts precipitate the salts of 

 ethylsulphocarbamic acid. When these are boiled with 

 water, they are resolved into sulphides, sulphuretted 

 hydrogen, and ethyl mustard-oil (p. 214). 



Carbamide (Urea). 

 = CO(NH 2 ) 2 . 



Occurrence. In many of the animal fluids, especially 

 in urine. (See Animal Chemistry Urine). 



Formation. From ammonium cyanate by the eva- 

 poration of its aqueous solution ; from cyanamide by 

 assimilation of the elements of water (p. 217); by the 

 action of ammonia on phosgene or carbonic ether ; from 

 oxamide by means of heating with mercury oxide ; by 

 heating ammonium carbamate or commercial ammo- 

 nium carbonate to 130-140. 



Preparation. 1. Extraction from urine. Urine is 

 evaporated to syrupy consistence, and, when cool, mixed 

 with an excess of strong nitric acid. Urea nitrate 

 separates in the form of dark brown crystalline masses. 

 It is now filtered off, pressed, and purified by recrystal- 

 lization from moderately strong nitric acid. It is most 

 easily obtained colorless, but not without loss, by 

 gradually adding small quantities of finely powdered 

 potassium chlorate to the hot concentrated solution in 

 nitric acid, then allowing to cool and recrystallizing 

 the almost colorless crystals which now separate, either 

 from water or nitric acid. The urea nitrate, purified 

 in this manner, is now decomposed by heating with 

 water and barium carbonate, the filtrate evaporated to 

 dry ness and the urea extracted from barium nitrate by 



