412 
Book II. 
ALKALIES. 
is decomposed by means of the oxides of manganese, 
arsenic, or gold, azotic gas is set at liberty, while the 
oxide is reduced*. Hence he concluded, that it is com 
posed of azot and phlogiston ; and Bergman coincided 
with him in opinion. Dr Priestley discovered, that 
when electric explosions are made to pass through this 
gas, its bulk is gradually augmented to thrice the 
space which it formerly occupied; and a quantity 
of hydrogen gas is produced. The same ingenious 
philosopher applied heat to the red oxides of mercury 
and lead confined in ammoniacal gas. The oxides were 
reduced, water was evolved, the ammoniacal gas disap 
peared, and, instead of it, there was found a quantity of 
azotic gast. These experiments, and those of Scheele, 
led to the conclusion, that ammonia is composed of 
azot and hydrogen : a conclusion which was fully esta 
blished by the experiments of Berthollet, published in 
the Memoirs of the French Academy for 1785. This 
acute philosopher repeated the experiments of Scheele 
and Priestley, and applied to them the theory of Mr 
Lavoisier, and added also several very decisive ones of 
his own. The most important of these is the mutual 
decomposition of ammonia and oxy-muriatic acid. When 
these bodies are mixed together, an effervescence takes 
place, azot is disengaged, a quantity of water formed, 
and the oxy-muriatic acid is converted into common 
muriatic acid. Now the substances mixed were am 
monia and oxy-muriatic acid, which is composed of 
oxygen and muriatic acid; the products were, muri 
atic acid, azot, and water, which is composed of oxy 
* Scheele, i. 95. and 155. French Transl.—Scheele on Fire, p. 137. 
t Priestley, ii. 396.