The method of heating red mercuric oxide to obtain oxygen is not practical because mercuric oxide is expensive, and the amount of oxygen given off is too small. Also, the mercuric oxide has to be heated to a very light temperature before oxygen is liberated.
When compounds containing oxygen, e.g. potassium chlorate, potassium permanganate, potassium nitrate and sodium nitrate, are heated, oxygen is given off. The usual method of preparing oxygen in the laboratory is to heat potassium chlorate, a compound which contains a large amount of oxygen. When some white crystals of potassium chlorate are heated strongly in a hard glass tube, the crystals melt and a gas is given off. When a glowing wooden splinter bursts into the test tube, showing the gas is oxygen. The white residue left behind in the test tube is potassium chloride. Oxygen is a very active element because it readily combines with most other elements to form oxides. This chemical process is called oxidation. Burning, rusting and respiration are everyday examples of oxidation. Oxygen does not burn, but it supports combustion.
When compounds containing oxygen, e.g. potassium chlorate, potassium permanganate, potassium nitrate and sodium nitrate, are heated, oxygen is given off. The usual method of preparing oxygen in the laboratory is to heat potassium chlorate, a compound which contains a large amount of oxygen. When some white crystals of potassium chlorate are heated strongly in a hard glass tube, the crystals melt and a gas is given off. When a glowing wooden splinter bursts into the test tube, showing the gas is oxygen. The white residue left behind in the test tube is potassium chloride. Oxygen is a very active element because it readily combines with most other elements to form oxides. This chemical process is called oxidation. Burning, rusting and respiration are everyday examples of oxidation. Oxygen does not burn, but it supports combustion.