MURIATE OF AMMONIA. 83 



muriate of lime is left. Carbonate of ammonia pos- 

 sesses the peculiar pungent smell of pure ammonia, 

 though far less powerfully ; because, being but partial- 

 ly neutralized by carbonic acid, and united to it by 

 but a feeble affinity, it is constantly gradually escap- 

 ing from its compound, and evaporating into the air. 

 Like the carbonates of potash and soda it possesses 

 the property of reddening many vegetable yellows, 

 though less powerfully than the pure alkali. 



156. The muriate of ammonia, commonly called 

 sal-ammoniac, which used also formerly to be obtained 

 by burning animal substances, is now procured from 

 the refuse of the gas-works, which contains carbonate 

 and other salts of ammonia. They are first of all 

 converted into a sulphate, by the action of oil of vitriol, 

 which expels the carbonic and other weaker acids; 

 and the sulphate thus obtained is decomposed by mix- 

 ing it with cogimon salt, and heating the mixture. 



157. The nature of this operation is very simple. 

 Sulphate of ammonia, water, and common salt, or 

 chloride of sodium, are heated together, and are de- 

 composed, because sulphuric acid has a stronger affi- 

 nity for soda than it has for ammonia ; a portion of 

 water is decomposed at the same time with the salt, 

 supplying oxygen to the sodium to form soda, and 

 hydrogen to the chlorine to form muriatic acid ; the 

 former unites with the sulphuric acid, whilst the latter 

 combines with the ammonia. 



158. Muriate of ammonia, like many other of the 

 salts of ammonia, is volatile at a certain heat ; that 



