LaMotte 1200 Colorimeter - Manual (Page 12)

SAMPLE DILUTION TECHNIQUES & VOLUMETRIC
MEASUREMENTS
If a test result using the 1200 Colorimeter gives an
ER2 (over range) message, the
sample must be diluted. Then the test should be repeated to obtain a reading
which is in the concentration range for the test. (Note: This is not true for
colorimetric determination of pH.)
Example:
Measure 5 mL of the water sample into a graduated cylinder. Add demineralized
water until the cylinder is filled to the 10 mL line. The sample has been diluted
by one-half, and the dilution factor is therefore 2. Perform the test procedure,
then multiply the resulting concentration by 2 to obtain the test result.
The following table gives quick reference guidelines on dilutions of various
proportions. All dilutions are based on a 10 mL volume, so several dilutions will
require small volumes of the water sample. Graduated pipets should be used for
all dilutions.
Size of Sample
Deionized Water to
Bring Volume to 10
mL
Multiplication
Factor
10 mL 0 mL 1
5 mL 5 mL 2
2.5 mL 7.5 mL 4
1 mL 9 mL 10
0.5 mL 9.5 mL 20
If the above glassware is not available, dilutions can be made with the
colorimeter tube. Fill the colorimeter tube to the 10 mL line with the sample
then transfer it to another container. Add 10 mL volumes of demineralized water
to the container and mix. Transfer back 10 mL of the diluted sample to the
colorimeter tube and follow the test procedure. Continue diluting and testing
until a reading, which is in the concentration range for the test, is obtained. Be
sure to multiply the concentration found by the dilution factor (the number of
total 10 mL volumes used).
Example:
10 mL of sample is diluted with three 10 mL volumes of demineralized water; the
dilution factor is four.
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