There are three methods of obtaining oxygen:
1 From _potassium chlorate_, or, as it is commonly called,
chlorate of potash.
When potassium chlorate (KCLO₃) is heated in a closed vessel
(closed vessel means "closed at one end"), it breaks up into
potassium chlorid and oxygen; that is, KCLO₃ + heat = KCL + O₃.
Potassium chlorate is used in fireworks because it gives up
its oxygen readily. Potassium nitrate serves the same purpose in
gunpowder, which is a mixture of sulfur (S), charcoal (C), and
salt-peter or potassium nitrate (KNO₃). The explosion of gunpowder,
after a certain temperature has been reached, is due to the
formation of oxygen, which, combined with the potassium nitrate, is
set free by the very rapid burning of the charcoal and the sulfur.
Other gases formed by the explosion are nitrogen, and probably
sulfur dioxid (SO₂), and oxids of nitrogen, N₂O, NO₂, etc. Carbon
monoxid and carbon dioxid are sometimes formed. Potassium nitrate,
however, is the most active agent in gunpowder.