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 saltpeter 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 mon-oxid and carbon dioxid are sometimes formed. Potassium nitrate, however, is the most active agent in gunpowder.

2 By the electrolysis of water.

By this method the oxygen and the hydrogen are separated by electricity.

3 By the liquefaction of air, which is a very recent and a very scientific method.

By this method the air is cooled down until it liquefies. At normal atmospheric pressure it liquefies at a temperature of - 312.6°F., but under pressure of about 585 pounds it liquefies at a temperature of - 220°F. After the air has been liquefied, it is allowed to go back to vapor by exposing it to the surrounding heat of the atmosphere, and this vaporization separates the nitrogen from the oxygen, as the nitrogen boils at a temperature of - 318°F., while the oxygen boils at a temperature of - 294°F. There is a difference of about 24° in the boiling points of these two gases, which at this low point amounts to more than the difference between the boiling points of alcohol and water, and this difference is sufficient to separate the oxygen from the nitrogen.

Production of oxygen by the liquefaction of air is the latest, cheapest, and most approved method, and is now becoming extensively used in obtaining both oxygen and nitrogen for commercial use.

Oxygen is tasteless and odorless. It is slightly heavier than air. When subjected to an extremely high pressure and low temperature it becomes liquid.