Absorption – The “soaking up” of gas, liquids or dissolved substances into a solid material.
Acid – A chemical compound that dissociates in aqueous solution to form hydrogen ions; a proton donor that reacts with a base to form a salt.
Adsorption – The condensation of gas, liquids or dissolved substances on the surface of solids.
Aerobic Gas Mixture – Gas mixture containing oxygen; used for incubation of microorganisms that require oxygen for life.
Air – The mixture of gases that surrounds the earth. The composition of air is 78.08% nitrogen, 20.95% oxygen, 0.03% carbon dioxide, and 0.93% argon. Standard air has a density of 0.075 lb/ft 3 (1.2 kg/m 3 ) measured dry at 70°F (21°C) and 760 mm Hg pressure, M.W. 28.3.
Anaerobic Gas Mixture – A gas mixture containing no oxygen, used for incubation of microorganisms that do not require free oxygen for life.
Anhydrous – A descriptive term meaning without water.
Balance Gas – A gas used to “top off” a gas mixture after individual component gases at specified concentrations are added.
Base – A chemical compound that can react with an acid to form a salt.
Boiling Point – The temperature at which the vapor pressure of a liquid equals the atmospheric pressure (usually given at 760 mm Hg).
Calibration Gas – A gas of accurately known concentration that is used as a comparative standard in analytical instrumentation.
Carrier Gas – Pure gases or gas mixtures used to move a sample to be analyzed through the gas analysis system at an even rate and provide a zero reference (baseline) when a sample is not being detected.
CGA – Short for Compressed Gas Association, an association that recommends cylinder valve outlet connections for specific gas services based on safety considerations.
Compressed Gas – Any material or mixture having in the container either an absolute pressure exceeding 40 psia (3 bar) at 70°F (21°C) or an absolute pressure exceeding 104 psia (7 bar) at 130°F (54°C).
Compressed Gas in Solution – A non liquefied compressed gas that is dissolved in a solvent.
Corrosive – Gases that corrode material or tissue with which they come in contact, or do so in the presence of water, are classified as corrosive. It is essential that equipment used for handling corrosive gases be constructed of proper materials. Proper protective clothing and equipment must be used to minimize exposure to corrosive materials.