50 HOW CROPS FEED. 



feather wet with vinegar or dilute chlorlijdric acid becomes surrounded 

 with a dense smolce when approached to the mouth of the bottle, the 

 latter may be removed, corlced, and another put in its place. Three or 

 four pint bottles of gas thus collected will serve to illustrate its proper- 

 ties, as shortly to be noticed. 



Solubility in Water. — This character of ammonia is ex- 

 hibited by removing, under cold water, the stopper of o 

 bottle filled with tlie gas. The water rushes witli great 

 violence into the bottle as into a vacuum, and entirely fills 

 it, provided all atmospheric air had been displaced. 



The aqita ammotihi, or spirits of hartshorn of the drug- 

 gist, is a strong solution of ammonia, prepared by passing 

 a stream of ammonia gas into cold water. At the freez- 

 ing point, water absorbs 1,150 times its bulk of ammonia. 

 When such a solution is warmed, the gas escapes abund- 

 antly, sc that, at ordinary summer temperatures, only one- 

 half the ammonia is retained. If the solution be heated 

 to boiling, all tlie ammonia is expelled before the water has 

 nearly boiled away. Th« gas escapes even from very di- 

 lute solutions wlien they are exposed to the air, as is at 

 once recognized by the sense of smell. 



Composition. — When ammonia gas is heated to redness 

 by being made to pass through an ignited tube, it is de- 

 composed, loses its characteristic odor and other proper- 

 ties, and is resolved into a mixture of nitrogen and hydro- 

 gen gases. These elements exist in ammonia in the pro- 

 portion of one part by bulk of nitrogen, to three parts of 

 hydrogen, or by weight fourteen parts or one atom of 

 nitrogen and three parts, or three atoms of hydrogeiK 

 The subjoined scheme exhibits the composition of ammo 

 nia, as expressed in symbols, atoms, and percentages. 



Symbol. At. vj't. Per cent. 



N = 14 .. 83.39 



H3 = 3 .. 17.61 



NH3 = 17 .. 100.00 

 Formation of Ammonia.— 1. When hydrogen and ni- 

 trogen gases are mingled together in the proportions to 



