NITROGEN. 75 



Ammonia, NH 3 = 17. This compound is constantly formed 

 in nature by the decomposition of organic (chiefly animal) 

 matter, such as meat, urine, blood, etc. It is also obtained 

 during the process of destructive distillation, which is the heat- 

 ing of non-volatile organic substances in closed vessels. The 

 manufacture of illuminating gas is such a process of destructive 

 distillation ; coal is heated in retorts, and the larger amount of 

 nitrogen contained in the coal is converted and liberated as 

 ammonia gas, which is condensed by passing the gases through 

 water. 



Another method of obtaining ammonia is the decomposition 

 of ammonium salts by the oxides or hydrates of sodium, potas- 

 sium, or calcium. Usually ammonium chloride is mixed with 

 calcium hydrate and heated, when calcium chloride, water, and 

 ammonia are formed : 



2(NH 4 C1) + Ca2HO = CaCl, + 2H 2 O + 2NH 3 . 



Ammonia is a colorless gas, of a very pungent odor, an alka- 

 line taste, and a strongly alkaline reaction. In pure oxygen it 

 burns, forming water and free nitrogen. 



By the mere application of a pressure of seven atmospheres 

 or by intense cold ( 40), ammonia may be converted into a 

 liquid, which at 80 forms a solid crystalline mass. Water 

 dissolves about 700 times its volume of ammonia, forming 

 ammonium hydrate : 



NH S + H 2 = NH 4 HO. 



Water of ammonia, Aqua ammonise (Spirit of hartshorn}. This 

 is a solution of ammonia gas in water or hydrate of ammonium 

 in water. The common water of ammonia contains 10 per 

 cent, by weight of ammonia, and has a specific gravity of 0.959 ; 

 the stronger water of ammonia contains 28 per cent., and has a 

 specific gravity of 0.900. Ammonia water has the above- 

 mentioned odor, taste, and reaction like the gas itself. 



Compounds of nitrogen and oxygen. Five distinct compounds 

 of nitrogen and oxygen are known. They are named and con- 

 stituted as follows : 



