Absorption
The penetration of matter in bulk into other matter, as in the  issolving of a gas in liquid.

Adsorption
The surface retention of solid, liquid, or gas molecules, atoms, or ions by a solid or liquid.

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).

British Thermal Unit (Btu)
The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.

Calorie
The amount of heat required to raise the temperature of one gram of water one degree Celsius.

Carrier Gas
Gas used with a gas chromatograph
used to carry the sample through the system.

CAS Number
A number assigned by the Chemical
Abstract Service which is unique to
each chemical and allows for more
efficient searching on other databases.

Catalyst
A substance that initiates a chemical reaction and allows it to proceed under different conditions than otherwise possible.

Chemiluminescence
A species which chemically absorbs
and emits light (usually) at low
temperatures).

Chromatogram
The record produced by the gas liquid chromatograph. It is also a measure of instrument performance.

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.

Halocarbons
Any hydrocarbon combined with any
of the five (F2, Cl2, Br, I At) elements in the VIIA group of the periodic table.

Heat of Fusion
The heat energy required to transform one mole of solid substance into one mole of liquid at one atmosphere of pressure.

Heat of Vaporization
The heat energy required to transform one mole of substance from the liquid phase to the vapor phase at one atmosphere of pressure.

Hydrocarbon
An organic compound containing
carbon and hydrogen.

Inert Gas
A gas that exhibits great stability and extremely low reaction rates under normal temperature and pressure conditions.

Inorganic Substance
Substances that do not contain carbon in their chemical structure.

Kelvin (K)
A unit of temperature related to the
triple point of water.

The Level of Detection
Practically defined as the amount of
sample in which the peak height is two or three times the noise height

Liquefied Compressed Gas
A gas which, under the charged
pressure, is partically liquid at a
temperature of 700F (21.10C).

Melting Point
The temperature at which the solid and liquid phase of a substance are in equlibrium (normally specified at one [1] atm).

Micron
One millionth of a meter.

Column
Part of the gas chromatograph system where the separation of the sample takes place (can be packed or capillary).

Compressed Gas
Any gas or gas mixture that, when
enclosed in a container, has a pressure exceeding 40 psia at 700F or regardless of the pressure at 700F, has a pressure exceeding 104 psia at 1300F, or any liquid  lammable material having a vapor pressure exceeding 40 psia at
1000F.

Compressed Gas Association (CGA)
An organization dedicated to the
development and promotion of safety standards and safe practices in the industrial gas industry. One of their focus areas is valve  onnections. The CGA and DISS outlet valves are governed by this system. CGA outlet valves are generally used with lowpurity
products.

Corrosive
A substance that erodes and deteriorates materials, such as metals, fabrics, and human tissue, upon contact.

Critical Density
The density of a pure material at its
critical temperature and critical
pressure.

Critical Pressure
At the critical temperature, the highest pressure at which a pure mateirla can exist as a gas in equilibrium with its liquid.

Critical Temperature
The highest temperature at which a gas can be liquefied.

Cryogenic Liquid
A liquid having a normal boiling point below - 2400F (-151.110C).

Density
The mass of a substance divided by its volume, or the mass of a substance per unit volume.

Dewar
Vessel which contains cryogenic liquid gases.

Molecular Weight
The sum of the atomic weights of all the atoms that constitute a molecule.

Nanogram (ng)
One billionth of a gram (10-9).

Nanometer (nm)
One billionth of a meter (19-9).

Oxidant or Oxidizing Agent
A substance that supports or causes combustion of other measures. Some common oxidizing agents are oxygen, nitrous oxide, and fluorine.

Pyrophoric
A substance that can spontaneously self-ignite when exposed to normal atmospheric conditions.

Pyrophoric Gas
A gas that can spontaneously selfignite when exposed to normal
atmospheric conditions.

Restrictive Flow Orifice (RFO)
A safety device place in the outlet of a cylinder valve that is intended to limit the release rate of a hazardous gas to a maximum specified range in the event of the inadvertent opening of the valve or failure of the system downstream of the valve outlet.

Sensitivity
Amount of response per amount of
analyze.

Specific Gravity
The ratio of the weight of one
substance compared to the weight of another substance which is used as a standard. Normally, liquids are
compared to water; gases are
compared to air.

Specific Heat
The ratio of the heat capacity of a
substance to the heat capacity of
water; or the quantity of heat
required for one degree temperature change in a unit weight of material.

Specific Volume
The volume occupied by a unit mass of a substance.

Dewpoint
The temperature at which air is
saturated with moisture, or the
temperature at which the water vapor in the air begins to condense.

Diameter Index Safety System (DISS)
DISS outlet valves are generally used with high-purity products, toxics, and corrosives. Valves equipped with DISS outlet assignment provide a metal-tometal
seal that creates low particles, a
permeation-free environment, and good leak integrity.

Dopant
An impurity added (usually in small
amounts) to a pure substance to alter its properties.

Eductor Tube
An eductor tube or dip tube permits the withdrawal of liquefied compressed gases in the liquid phase with the cylinder in the normal upright position, without having to invert the cylinder.
Air Products offers two types of eductor tubesgooseneck tubes, and full-length tubes.

Effluent Splitter
The part of the analytical instrument that splits the effluent stream into multiple detectors or some to vent for a lower volume of effluent.

Electron Volt (eV)
A voltage measurement.

Flammable Gas
As defined by the DOT, any compressed gas that either forms a flammable mixture with air at a concentration of 13% or less (by volume), or has a flammable range in air wider than 12%, regardless of the lower explosive limit (LEL).

Threshold Limit Valve-Ceiling
(TLV-C)
The airborne concentration of
asubstance that should not be
exceeded during any part of the
working exposure (ACGIH 1985-
1986).

Threshold Limit Value-Time
Weighted Average (TLV-TWA)
The time-weighted average airborne concentration of a substance for a normal eight-hour workday or a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.

Toxic
A substance that has the ability to
produce injurious or lethal effects
through its chemical interaction with the body.

Triple Point
The temperature and pressure at
which the liquid, solid, and vapor
phase of a substance are in
equilibrium.

Vapor Pressure
The pressure exerted by the vapor
above a liquid when the two phases
are in equilibrium. The valve depends on the temperature of the system.