25 May 2005
designation. These generic chemicals may be blended or used separately. They are
usually much less expensive than special chemical blends developed by manufacturers
under a trade name.
of water, chiefly due
to the existence
of carbonate and
sulfate (and occasionally the nitrite and chloride) salts of calcium, iron, and magnesium.
(b) Commonly computed from the amount of calcium and magnesium in the water and
expressed as equivalent calcium carbonate. (c) Causes "curding" of water when soap is
used, increased consumption of soap, deposition of scale in boilers, injurious effects in
some industrial processes, and sometimes objectionable taste in the water.
Hardness, Carbonate -- Hardness caused by the presence of carbonates and
bicarbonates of calcium and magnesium in water. Such hardness may be removed to
the limit of solubility by boiling the water. This is also called temporary hardness.
Hardness, Non-Carbonate -- Hardness caused by calcium and magnesium sulfates
and chlorides and compounds other than carbonates which cannot be reduced
materially by boiling the water. (Also called "permanent hardness".)
Hardness, Total -- The sum of carbonate and non-carbonate hardness.
Hydrogen Ion Concentration
-- Commonly expressed
pH value that represents
the logarithm of the reciprocal of the hydrogen ion concentration.
Inhibitor (applied to corrosion) -- A chemical substance or mixture that effectively
decreases corrosion when added to a liquid (usually in small concentrations).
Ion -- A particle, atom, or group of atoms, carrying either a positive or negative
electrical charge, formed when an electrolyte is dissolved in water.
Ion Exchange -- A process where water is passed through a granular material wherein
ions on the granular material are replaced by ions contained in the water. For example,
in the zeolite softening process, the sodium ions (Na+) of the granular zeolite are
replaced by the calcium ions (Ca++) in the water to leave the water free of calcium (the
cause of hardness), but with an increased amount of sodium.
Langelier Index (saturation index) -- An index based on the calcium hardness, total
alkalinity, total dissolved solids (TDS), temperature, and pH. It is used to classify waters
by their ability to either dissolve or deposit calcium carbonate. It is the algebraic
difference between the actual pH and the calculated pH of saturation (pHs) (LI = pH -
pHs). A positive value indicates a scale-forming tendency, a negative value indicates a
scale-dissolving tendency. It was one of the first indices developed for this purpose and
was designed specifically for municipal water flowing in distribution lines.
Makeup Water -- Water supplied to replace the loss in a system due to leaks,
evaporation, wind drift, bleed-off, blowdown, or withdrawal.