Glossary of Terms

1. Absorption
   The penetration of matter in bulk into other matter, as in the dissolving of a gas in liquid.
2. Adsorption
   The surface retention of solid , liquid, or gas molecules, atoms or ions by a solid or liquid.
3. Boiling Point
   The temperature at which the vapor pressure of the liquid is equal to the prevailing pressure of the atmosphere. The normal boiling point is the temperature at which the vapor pressure of the liquid is 14.7 psia (1 atm).
4. British Thermal Unit (Btu)
   The amount of heat required to raise the temperature of one pound of water one degree Celsius.
5. Calorie
   The amount of heat required to raise the temperature of one gram of water one degree Celsius.
6. Carrier Gas
   Gas used with a gas chromatograph used to carry the sample through the system.
7. Catalyst
   A substance that initiates a chemical reaction and allows it to proceed under different conditions than otherwise possible.
8. Chromatogram
   The record produced by the gas chromatograph. It is also a measure of instrument performance.
9. Column
   It is a part of the gas chromatograph system where the separation of the sample takes place (can be packed or capillary).
10. Compressed Gas
    Any gas or gas mixture that, when enclosed in a container, has pressure exceeding 40 psia at 70° F or regardless of the pressure at 70° F, has a pressure exceeding 104 psia at 130° F, or any liquid flammable material having a vapor pressure exceeding 40 psia at 100° F.
11. Critical Density
    The density of a pure material at its critical temperature and critical pressure.
12. Critical Pressure
    At the critical temperature, the highest pressure at which a pure material can exist as a gas in equilibrium with its liquid.
13. Critical Temperature
    The highest temperature at which a gas can be liquefied.
14. Cryogenic Liquid
    A liquid having a normal boiling point below –240 °F (-151.11 °C).
15. Density
    The mass of a substance divided by its volume, or the mass of substance per unit volume.
16. Dewar
    Vessel which contains cryogenic liquid gases.
17. Dew-point
    The temperature at which the water vapor in the air begins to condense.
18. Eductor Tube (Dip Tube)
    A tube fixed to the cylinder valve either straight or curved towards the wall of the cylinder permitting the withdrawal of the liquid phase of a liquefied gas.
19. Electron Capture Detector
    A detector used in a gas chromatograph system which is very sensitive to halogen containing compound.
20. Flammable Limits
    The concentration of flammable vapor in air, oxygen, or other oxidant that will propagate flame upon contact. The lower explosive limit (LEL) is the concentration below which a flame will not propagate. The upper explosive limit (UEL) is the concentration above which a flame will not propagate. A change in temperature or pressure may vary the flammable limits.
21. Flash Point
    The lowest temperature at which a flammable liquid will give off enough vapor at or near its surface to form an ignitable mixture with air.
22. Flow Meter
    An instrument used to measure flow rate. The measurement is either by floating ball (Rota-meter) or by heat transfer (Mass Flow-meter).
23. Hydrocarbon
    An organic compound containing carbon and hydrogen.
24. Halocarbons
    It is a general name for organic compound containing Carbon and Fluorine, Chlorine or Bromine. Trade name includes FREON, HALON, and UCON.
25. High Purity
    The gases of higher purity than industrial gases with guaranteed specification (impurity levels).
26. Inert Gas
    A gas which does not take parts any reaction under most or all conditions.
27. Inorganic Substance
    Substances that do not contain carbon in their chemical structure.
28. Liquefied Compressed Gas
    A gas which, under the charged pressure, is partially liquid at a temperature of 70 °F.
29. Manifold
    A system of valve and piping that allows several cylinders to be connected to a common line and direct the flow of gas.
30. Molecular Weight
    The sum of the atomic weights of all the atoms that constitute a molecule.
31. Oxidizing Gas
    A gas that supports combustion and that can lead to fire or explosion when it comes into contact with combustible material.
32. Pyrophoric
    A substance that can spontaneously self-ignite when exposed to normal atmospheric conditions.