2023 Online Catalog - Flipbook - Page 484
17 Glossary of Important Terms
Angstrom Unit:
A unit of wavelength of light equal to one tenth of a millimicron
or one ten-millionth of a millimeter.
Etching:
The deterioration by chemical change on the surface of
glassware caused by the action of high temperatures and
detergents, and it is more prevalent or intensified in soft or
softened water supplies. Very high water temperatures in
automatic dishwashers can cause detergent phosphate
compounds to change into even more aggressive forms. If
enough dish soil or water hardness is available, it will react
with the most aggressive of these sequestering phosphates.
Otherwise, however, the excessive detergent agents can
actually extract elements directly from the glassware
composition. In early stages, incipient etching appears as
a rainbow colored film similar to an oil-on-water film. As
etching progresses, this changes to opaqueness, which
appears similar to filming except that it cannot be removed or
repaired since etching is an actual eating away of the glass.
It is sometimes called “soft water filming”. The solution to
chemical etching is to use less detergent, water temperatures
below 140°F, and sufficient amounts of water during the
rinse cycle. (Poor rinsing can also be caused by overloading
the dishwasher.) Mechanical etching can occur when two
glasses rub against each other in the dishwasher. (See also
Water Spotting.)
Flux:
Gallons per day of permeate passing through each square foot
of membrane surface.
Iron Bacteria:
Organisms which are capable of utilizing ferrous iron, either
from the water or from steel pipe, in their metabolism and
precipitating ferric hydroxide in their sheaths and gelatinous
deposits. These organisms tend to collect in pipelines and
tanks during periods of low flow and to break loose in slugs
of turbid water to create staining, taste and odor problems.
Technical & Engineering
Jackson Turbidity Unit (JTU):
An arbitrary unit of turbidity originally based on a suspension
of a specific type of silica with the turbidity measured in a
Jackson Candle Turbidimeter. Now called a Nephelometer.
Langelier’s Index:
A calculated number used to predict whether or not a
water will precipitate, be in equilibrium with, or dissolve
calcium carbonate. It is sometimes erroneously assumed
that any water which tends to dissolve calcium carbonate is
automatically corrosive.
Micron:
A linear measure equal to one millionth of a meter or .00003937
inch. The symbol for the micron is the Greek letter “µ”.
Sequestering Agent:
A chemical compound sometimes fed into water to tie up
undesirable ions, keeps them in solution, and eliminates
or reduces the normal effects of these ions. For example,
polyphosphates can sequester hardness and prevent reactions
with soap.
Uniformity Coefficient:
The degree of variation in the size of the grains that constitute
a granular material; the ratio of (a) the diameter of a grain size
that is barely too large to pass through a sieve that allows
60 percent of the material (by weight) to pass through, to
(b) the diameter of a grain of a size that is barely too large to
pass through a sieve that allows 10 percent of the material
(by weight) to pass through. The coefficient is unity for any
material having grains all the same size, and it increases
above unity with variation in size of grain.
Virus:
The smallest form of life known to be capable of producing
disease or infection, usually considered to be of large
molecular size. They multiply by assembly of component
fragments in living cells, rather than by cell division, as do
most bacteria.
Water Hammer:
The shock wave or series of waves caused by the resistance
of inertia to an abrupt change (acceleration or deceleration)
of water flow through a water piping system. Water hammer
may produce an instantaneous pressure many times greater
than the normal pressure. For this reason, many building codes
now require the installation of a “water hammer arrestor,” a
device to absorb these shock waves and prevent damage to
appliances such as washing machines.
Water Spotting:
Cloudy milk-like film, spots, streaks, or heavy white deposits
left on surfaces after water has dried from them, especially
noticeable on clear glassware and cars after washing.
Spotting is caused by minerals that had been dissolved in the
water remaining behind after the water has evaporated. Soft
water spotting can be wiped off easily with a damp cloth or
rinsed off with a little fresh water. Hard water deposits, on
the other hand, are comprised of the more tenacious calcium
and magnesium salts. Hard water films typically require harsh
abrasives or an acid cleaner to remove them. A third type
of water residue film is due to silica (Si02) deposits. Silica
spotting is rare, but it is more difficult or impractical to be
removed when it does occur. If glassware films won’t dissolve
in acids such as vinegar or lemon juice, they may be due to
silica spotting or etching. If the spot won’t dissolve in acid,
but can be scratched off with a razor blade or pinpoint, it’s
likely a silica film. (See also Etching.)
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