- 



AMMONIA 



303 



Sometimes, a stream of the gas is generated by warming com- 

 mercial ammonium hydroxide solution (aqua ammonia), and dry- 

 ing the gas as above. Liquefied ammonia is obtainable in small 

 iron cylinders, and is a convenient 

 source when much of the gas is 

 required. 



The liberation by hydrolysis of 

 nitrides, already noted (p. 287), is 

 interesting : 



Mg 3 N 2 +6H 2 0- 3Mg(OH) 2 +2NH 3 . 



Composition of Ammonia. 



That ammonia contains nitrogen may 

 be shown by passing the gas over 

 cupric oxide heated in a tube, and 

 collecting the nitrogen over water: 



2NH 3 + 3CuO - 3Cu + 3H 2 O + N 2 . 



FIG. 78 



The hydrogen may be liberated by drying the ammonia, if 

 necessary, with soda-lime, and leading it through a tube containing 

 heated magnesium ribbon : 



2NH 3 + 3Mg - Mg 3 N 2 + 3H 2 . 



Physical Properties. Ammonia is a colorless 

 gas. It has a soapy taste, and a very pungent odor. 

 Its density, recorded in the formula NH 3 , indicates 

 that it is only about Jialf as Jaeayy. bulk for bulk, 

 as_air (14 + 3 = 17 against 28.95). It is easily 

 liquefied, boiling at 38.5, and exerting a pressure 

 of 6 atmospheres at 10. The gas is exceedingly 

 soluble in water (1 vol. water dissolves 1300 vol. of 

 NH 3 at 0). A 35 per cent solution is sold as " con- 

 centrated ammonia." 



The extreme solubility in water may be shown by 

 the " fountain " experiment (Fig. 79). The flask is filled with am- 



FIG. 79 





