414 
Book II. 
ALKALIES. 
ammonia is immediately exhaled. The nitric acid and 
the water which it contains are decomposed ; the oxy 
gen of each unites with the tin, and reduces it to the 
state of an oxide ; and at the same time the hydrogen 
of the water combines with the azot of the acid, and 
forms ammonia, which is driven off by the stronger af 
finity of the potass or lime. Dr Austin succeeded also 
in forming ammonia by several other methods. He 
introduced into a glass tube filled with mercury a little 
azotic gas, and then put into the gàs some iron-filings 
moistened with water. The iron decomposes the wa 
ter and combines with its oxygen; and the hydrogen, 
meeting with azot at the moment of its admission, com 
bines with it, and forms ammonia. This experiment 
shews, that the gaseous state of the azot does not pre 
vent its combination with hydrogen.