86 



NON-METALS AND THEIR COMBINATIONS. 



Ammonia, NH 3 = 17. This compound is constantly forming 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 heating of non-volatile organic 

 substances in suitable vessels to such an extent that decomposition 

 takes place, the generated volatile products being collected in re- 

 ceivers. The manufacture of illuminating gas is such a process of 

 destructive distillation ; coal is heated in retorts, and most of the 

 nitrogen contained in the coal is converted into and liberated as 

 ammonia gas, which is absorbed in water, through which the gas is 

 made to pass. 



Apparatus for generating ammonia. 



Another method of obtaining ammonia is through decomposition 

 of ammonium salts by the hydroxides of sodium, potassium, or cal- 

 cium. Usually ammonium chloride is mixed with calcium hydroxide 

 and heated, when calcium chloride, water, and ammonia are formed : 



2(NH 4 C1) + Ca(OH) 2 = CaCl 2 + 2H 2 O + 2NH 3 . 



