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Operator Manual
Appendix F: Glossary
Several of the terms used throughout this Operator Manual have specific meaning within high-
purity water applications. These unique terms include:
Conductivity A measure of the ability to conduct current through water. Conductivity,
very low with high-purity deionized water, is the reciprocal of resistivity and
is measured in microsiemens per centimeter (µS/cm).
High-Purity
Water (HPW) A term that differentiates between simple deionized water and the purer
water required for more critical processes. High-purity implies water that is
low in potential contaminants such as ions, microorganisms, organics and
particles.
Megohm (MW) A measurement of 1,000,000 ohms.
Microsiemens
(µS) A unit of conductance in the metric system equivalent to one millionth of an
ampere per volt (1 µS = 1 M.).
Organic Organic chemicals which include carbon atoms in complex molecules, but
do not include carbonate (CO
2
, HCO
3
, CO
3
) or cyanide (CN) related
compounds. Oxygen is very common in organics and they almost always
include hydrogen.
Oxidation The loss of electrons by a chemical species, typically with oxygen. Organic
carbon, for example, oxidizes to carbon dioxide and water.
Parts per billion
(ppb) A term used to report trace chemical analyses. It refers to the concentration
of the element or compound present within one billion parts of water. One
microgram per liter (µg/L) is equal to 1 ppb).
Resistivity Resistance, measured in megohmcentimeters (M
Ω
-cm), to the flow of
electrical current through high-purity water. Resistivity is a means of
continuously measuring the purity of the water and is the reciprocal of
conductivity.
Temperature
Compensation Conductivity and resistivity of electric current in water depend on the
temperature of the water. The lower the temperature, the lower the
conductivity and the higher the resistivity. Conductivity and resistivity
measurements typically are normalized to 25°C. In other words, they reflect
the values they would report at a sample temperature of 25 °C using a
model based on sodium chloride in water.
Total Organic
Carbon (TOC) A measurement of the organics present in water based on it carbon
content. High-purity water measures TOC in parts per billion (ppb). This
term is used interchangeably with total
oxidizable carbon.