XXII 



ACIDS, BASES, AND SALTS 



307 



and fills two-thirds of the volume of the tube, the gas remaining 



being nitrogen. As chlorine combines with an equal volume of 



hydrogen the volume of 



nitrogen in the ammonia 



is only one-third that of 



the hydrogen, that is, the 



gas is NH 3 , or N 2 H 6 , &c. 



The density of the gas 



(8 '5), however, indicates 



that the simplest formula 



must be taken. 



The white fumes formed 

 in the above experiment 

 and by the action of the 

 gas on hydrochloric acid 

 are fumes of ammonium 

 chloride, NH 4 C1, and its 

 production may be repre- 

 sented by the equation 



The solution of am- 

 monia has been already 

 shown to behave in a 

 manner closely analogous 

 to caustic soda, and if 

 added to a solution of a 

 magnesium salt, it also 



precipitates magnesium hydroxide. The solution therefore 

 behaves like a soluble hydroxide and we may regard it as such, 

 viz., as NH 4 OH, which results from the solution of the gas in 

 water : 



Fio. 141. Tube for Determining the 

 Composition of Ammonia. 



Ammonium. The formation of salts from ammonia is then 

 completely analogous to the formation of salts from caustic soda, 

 and the equation may be rewritten with the substitution of 

 NH 4 for the Na, thus : 



NH 4 OH + HC1 = NH 4 C1 + H 2 O. 



To this group of elements NH 4 , which we may regard as exist- 

 ing in these salts, the name ammonium is given, but it should 



r 2 



