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GAS STATE IN CYLINDER There are four cases: either the substance remains a gas at standard temperature but increased pressure, the substance liquifies at standard temperature but increased pressure, the substance is dissolved in a Solvent , or 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 Case I: the substance remains a gas at '''standard temperature''' but '''increased pressure''': # Air - yellow cylinder # Argon - brown cylinder # Helium - brown cylinder # Nitrogen - black cylinder (US) # Oxygen - blue cylinder (EU); green cylinder (US) Case II Case II: the substance liquifies at '''standard temperature''' but '''increased pressure''': # Butane - silver or gray cylinder # Propane - silver cylinder (sometimes dark blue) # Carbon Dioxide # Nitrous Oxide - blue cylinder (US) Case III Case III: the substance is dissolved at '''standard temperature''' in a solvent. # Acetylene - black cylinder (EU)
Case IV Case IV: the substance is liquified at '''reduced temperature''' and '''increased pressure''': # Liquid Nitrogen (LN2) # Liquid Oxygen (LOX)
EXPANSION AND VOLUME 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. SPECIAL HANDLING CONSIDERATIONS Because the contents are under high pressure and are sometimes hazardous, there are special Safety regulations for handling bottled gases. These include chaining bottles to prevent falling and breaking, proper ventilation to prevent injury or death in case of leaks and signage to indicate the potential hazards. The Compressed Gas Association sells a number of booklets and pamphlets on safe handling and use of bottled gases. (Members of the CGA can get the pamphlets for free.) NOMENCLATURE DIFFERENCES U.S. usage typically refers to bottled gas when discussing liquified petroleum gas. The usage of 'bottled gas' is sometimes used in medical supply also especially for portable oxygen tanks. Commonly, other industrial gases stored in cylinders are called 'gas cylinders' in the US. The UK and other parts of Europe more commonly refer to 'bottled gas' when discussing any usage whether industrial, medical or liquified petroleum. COLOR CODING Different countries have different gas color codes. See the
Note: In the U.S., colour coding is not regulated by law. Do not trust the colour of a cylinder to indicate what it contains. Check the label (a.k.a. decal) for product identification. EXTERNAL LINKS
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