Bottled gas

Bottled gas is a term used for substances which are gasous at Standard temperature and pressure (STP) and have been compressed and stored in steel bottles. There are three cases: the substance remains a gas at standard temperature but increased pressure, the substance liquifies at standard temperature but increased pressure, and the substance is liquified at reduced temperature and increased pressure. In the last case the bottle is constructed with an inner and outer shell separated by a vacuum so that the low temperature can be maintained by evaporative cooling.

Case I: the substance remains a gas at standard temperature but increased pressure:

1. acetylene black cylinder
2. air
3. argon brown cylinder
4. helium brown cylinder
5. oxygen green cylinder

Case II: the substance liquifies at standard temperature but increased pressure:

1. butane silver cylinder
2. propane silver cylinder

Case III: the substance is liquified at reduced temperature and increased pressure:

1. liquid helium
2. liquid nitrogen
3. liquid oxygen (LOX)