| Water Testing
There are two general methods used to determine
the levels of impurities and the type and amount of treatment necessary
to eliminate corrosion, scale and loss of heat transfer ability. These are
titration and colorimetric tests. The
colorimetric is the easiest to perform for plant engineers, so compliance
with routine testing is usually higher with this type of test.
- The colorimetric test is based upon the
development of a color in a sample proportional to the amount of the substance
present. Concentration of substance in the sample is found by comparing
its color with color standards of know concentration. Some comparators
have color standards in sealed glass ampoules (CHEMetrics): others use
standard colored disks.
- To perform a titration test, standard solutions
from a burette, drop test kit, or calibrated container are added to the
water sample. When the endpoint is reached, usually signalled by a color
change in the sample, the burette solution level is noted or number or
drops counted, if a drop test is used. The reading is proportional to the
amount of the particular impurity present.
There are three options to determine water
"hardness", including gravimetric analysis for calcium and magnesium,
colorimetric titration and soap tests, of which the latter two are the most
popular.
Conductivity is another method of measuring the total solids found
in a water sample. Pure, distilled water, is a poor conductor of electricity,
therefore the less dissolved solids in the water, the lower will be the
conductivity. The instrument used for this measurement is a conductivity
meter and the results are measured are micromhos (umhos).
When taking a sample for water testing, please
observe the following:
- Use a clean, rubber-stoppered, resistant
glass bottle or a new plastic bottle
- Either thoroughly wash and rinse used bottles
or use new bottles for samples
- Before taking samples through metal lines
and valves, allow water to run for several minutes to wash out the system.
This is necessary to make certain the sample taken is representative and
not contaminated with a disproportionate amount of any one impurity.
- Rinse the container throughly with the water
that is to be analyzed before taking a sample.
|
