Bottled gas
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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 or composite bottles known as gas cylinders. 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 (dewar flask) so that the low temperature can be maintained by evaporative cooling.
Case I: the substance remains a gas at standard temperature but increased pressure:
- acetylene black cylinder
- air yellow cylinder
- argon brown cylinder
- helium brown cylinder
- oxygen green cylinder
Case II: the substance liquifies at standard temperature but increased pressure:
Case III: the substance is liquified at reduced temperature and increased pressure:
The general rule is that one unit volume of liquid will expand to approximately 800 unit volumes of gas at Standard temperature and pressure with some variation due to intermolecular force and molecule size compared to an ideal gas. Normal high pressure gas cylinders or bottles will hold from 200 to 400 atmosphere (unit)s. The atmosphere units pressure held by the bottle is equivalent to the number of volumes of standard temperature and pressure of the gas held by the bottle for an ideal gas.
Because the contents are under high pressure and are sometimes hazardous, there are special safety regulations for handling bottled gases.
Note: Different countries have different gas color codes. See the Virtual Anesthesia Machine (http://vam.anest.ufl.edu)
Categories: Anesthesia | Gases | Welding