THE CHEMISTRY OF WATEK. HYDEOGEX. 127 



but is obtained for 

 the chemist's use by 

 heating sal ammo- 

 niac (or ammonium 

 chloride) with lime. 

 The materials may 

 be mixed in a glass 

 flask, and a gentle 

 heat suffices. The 

 gas is lighter than 

 air, and may be col- 

 lected by upward dis- 

 placement, as repre- 

 sented in Fig. 48. 

 The reaction is as fol- 

 lows : 



Fig. 43. 



2(H 4 NC1) + CaO = CaCl 2 + H a O 4- 2(H,N) 

 Ammonium salts will be studied farther on. 

 163. Water of Ammonia. Water eagerly absorbs ammo- 

 nia, and can dissolve nearly five hundred times its bulk of 

 this gas. The gas, in thus uniting with the water, becomes 

 greatly condensed, for it occupies a space nearly five hun- 

 dred times as small as it did before it was dissolved. We say 

 nearly, for the water is somewhat increased in bulk by dis- 

 solving the ammonia, the specific gravity of the solution be- 

 ing .870 compared with water reckoned as 1. This solution 

 is prepared in the apparatus represented in Fig. 49 (p. 128). 

 The ammonia is generated in the first flask, and enters 

 the water contained in the three -necked bottles (called 

 Woulfe -bottles), saturating them successively. The pun- 

 gent odor of this water of ammonia when in its full strength 

 is exceedingly strong. If it be applied to the skin, its irri- 



