xni THE DECOMPOSITION OF THE ALKALIS 285 



since the gas after sparking gave a cloud of sal-ammoniac when 

 mixed with hydrogen chloride ; he was even able to recombine 

 a mixture of hydrogen and nitrogen by sparking it in presence 

 of hydrogen chloride. 



3H 2 4- N 2 + 2HC1 -> 2NH 4 C1 



(Sal-ammoniac.) 



The presence of an inflammable constituent in ammonia had 

 already been recognised in 1774 by Scheele who found that the 

 mineral "manganese" could be dissolved by acids when combined 

 with ammonia, in the same way that it was dissolved in presence 

 of combustible substances. In this process the non-inflammable 

 constituent was liberated as an inactive gas : 



3MnO 2 +2NH 4 NO 3 -> Mn(NO 3 ) 2 +2MnO + 4H 2 O + N 2 



(Manganese (Ammonium (Manganous (Manganous (Water.) (Nitro- 



dioxide.) nitrate.) nitrate.) oxide.) gen.) 



The same inert gas was liberated when ammonia was oxidised 

 by the calx of gold during the detonation tf fulminating gold, an 

 explosive compound obtained by precipitating gold chloride 

 with ammonia. 



Au 2 O 3 ,2NH 3 -> 2Au + 3H 2 O + N 2 



(Fulminating (Gold.) (Water.) (Nitro- 



gold.) gen.) 



The gas prepared from fulminating gold was used by Ber- 

 thollet, when he sparked the inactive constituent of ammonia with 

 oxygen, and showed that it was diminished in the same way as 

 atmospheric nitrogen. Berthollet also showed that the inflam- 

 mable constituent was really hydrogen ; he oxidised ammonia 

 with nitric acid, by heating crystalline ammonium nitrate, and 

 collected the water produced 



NH 4 NO 3 -> 2H 2 O + N 2 O ; 



(Ammonium (Water.) (Nitrous 



nitrate.) oxide.) 



the other product was pure nitrous oxide. 



The discovery of the composition of ammonia, together with 

 that of muriatic acid (hydrogen chloride) showed that hydro- 

 salts could be produced by combining two hydrides, e.g. 



NH 3 + HC1 -> NH 4 C1 



(Am- (Hydrogen (Sal 



monia.) chloride.) ammoniac.) 



