LaMotte AM-21 Water Pollution Detection Outfit - Manual (Page 5)

Introduction
This kit employs two typical quantitative chemical test methods:
colorimetric comparison with standards of known value or titration of the
sample with solutions of known value. The reagent systems employed in
these testing sets can also be used to make simple qualitative tests where the
presence or absence (not the amount) of the factor being investigated is of
concern to the investigator. These qualitative tests can be conducted in the
field or in the classroom where the overhead projector can be used to project
the colorful reactions.
The colorimetric comparison outfits provide color standards of known
values. If the color of the test sample does not match the color of one of the
standards, but is between two color standards, the value assigned to the test
sample is the midpoint between the two standards that bracket the color of
the sample. For example, if the color of the test sample is between the colors
of 0.2 and 0.6 ppm, the result is read as 0.4 ppm. In the pH test, if the color
of the sample is between pH 7.6 and 7.8, the result is read as pH 7.7. When
the color of the test sample (other than pH) is greater than the standard of
the highest value, the test is repeated on a portion of the test sample that has
been diluted on a one-to-one ratio with distilled water. The values of the
color standards are multiplied by a factor of 2 to compensate for the dilution.
Dilutions of higher ratio can be made; however, it must be remembered that
the values of the standards must be multiplied by the ratio of the dilution. A
dilution procedure cannot be used when measuring pH.
The titration procedures are performed using a Direct Reading Titrator
which accurately measures the amount of titration reagent used. Carefully
read the enclosed instruction manual on the Direct Reading Titrator before
performing any of the titrations.
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