Oxygen gas characteristics
Oxygen gas (O2) has a boiling point of −183°C at normal atmospheric pressure. If the pressure is increased, the boiling point will also increase. At normal temperature O2 is therefore only available in gas form. Liquid oxygen is light blue without odour; the density of the liquid is 1.15 × 103 kg/m3 at boiling point, while the density of the gas is 1.36 kg/m3 at 15°C and normal atmospheric pressure. One litre of liquid oxygen will therefore expand 820 times when changing phase to gas at 15°C.
Liquids with boiling point below −100°C are commonly called cryogenic liquids. Handling cryo-genic liquids involves certain elements of risk:
· Extremely low temperature can result in frost injures on the skin when handling; the cold gas may also cause internal injuries
· Materials that come into contact with the liquid easily become brittle
· There is a danger of explosion when uncontrolled transformation from liquid to gas is allowed to occur in closed volumes.
By itself, O2 is inflammable but oxygen supports a fire and is normally the limiting factor for fire development. If much oxygen is available in the atmosphere, only a small spark can create an explo-sive fire. Care should therefore be taken when handling oxygen gas.