COMPOUNDS CONTAINING NITROGEN. 545 



the change indicated above. Ammonia and carbon dioxide unite to 

 form ammonium carbamate: 



2NH 3 + C0 2 = NH 4 .NH 2 .CO 2 . 

 By removal f water this salt is converted into urea : 

 NH 4 .NH 2 .CO a = (NH 2 ) 2 CO + H a O. 



Amino-formic acid or carbamic acid, NH 2 .COOH, is the acid 

 which, in the form of the ammonium salt, is a constituent of the com- 

 mercial ammonium carbonate. It is formed by the direct action of 

 carbon dioxide upon ammonia, as shown above. 



Urethanes are ethereal salts of carbamic acid, a class of comr 

 pounds having hypnotic properties. The class name is derived from 

 one member, which is official and generally known as " Urethane." 

 It is ethyl urethane, or 



Ethyl carbamate, ^Jthylis carbamas, CO.OC 2 H 5 .NH 2 = 88.42. 

 Obtained by the action of alcohol on urea or on one of its salts : 



It is a white crystalline powder, readily soluble in water, alcohol, or ether. 

 Heated with solution of potassium hydroxide, ammonia is liberated, while the 

 addition of sodium carbonate and iodine causes, on warming, the precipitation 

 of iodoform. 



Several similar compounds have been introduced under specific names, 

 thus: Euphorin, or phenyl-urethane, C 6 H 5 NH.COOC 2 H 5 , a crystalline powder, 

 sparingly soluble in cold water; neurodin, or acetyloxyphenyl-urethane, 



pr > colorless, sparingly soluble crystals ; thermodm, or phe- 



nacetin-urethane, C 6 H 4 C^ * <COOC 2 H ' colorless > verv sparingly sol- 



O FT 



uble needles ; hedonal, ormethylpropylcarbinol-urethane, NH 2 .COOCH<Q jj 



a difficultly soluble white powder. 



The amino-acids and acid-amides are of considerable interest because many 

 products of animal and plant life belong to these classes of compounds. Some 

 of these are considered in the subsequent chapters on Physiological Chemistry, 

 but may be briefly mentioned here. 



Sarcosine, Methyl-glycocoll, CI^NH.CI^CC^H, a product of the 

 decomposition of creatine, which is found in flesh, and of caffeine, and may be 

 obtained by boiling these compounds with a solution of barium hydroxide. It 

 is much like glycocoll in properties. 



Cystine, (SC(CH 3 )NH 2 CO 2 H.) 2 , a derivative of a-araino-propionic acid, 

 sometimes found in the sediment of urine (see Index). 

 35 



