LaMotte PHOSPHONATE TEST KIT OP-DR - Manual (Page 2)

USE OF THE OCTET COM PARA TOR
The Octet Comparator contains eight
permanent color standards. A test sample is
inserted into the openings in the top of the
comparator. The sample can then be compared
to four color standards at once, and the value
read off the comparator. For optimum color
comparison, the comparator should be
positioned between the operator and a light
source, so that the light enters through the
special light-diffusing screen in the back of the
comparator. Avoid viewing the comparator
against direct sunlight or an irregularly lighted
background.
pH AD JUST MENT
Prior to performing the actual test titration, the pH of the test sample
must be adjusted to approximately pH 2.6. The pH adjustment is made
by adding *Hydrochloric Acid to the test sample. The amount of
*Hydrochloric Acid to be added is determined as follows:
1.
Fill the test tube (0822) to the 10 mL line with the sample water.
2. Add 14 drops of Meta Cresol Purple Indicator (2202). A color
somewhere between yellow and purple will develop, depending on
the pH of the sample.
3. Add *Hydrochloric Acid (6310), one drop at a time, mixing
between drops, counting the number of drops, and continually
comparing the color of the sample against the two pH color
standards in the Low-High pH Comparator (7712). When the
sample color is between these two standard colors, the sample has
been adjusted to the proper pH. The sample color must not be too
yellow or too red.
4. Record the number of drops of *Hydrochloric Acid used in Step C.
The same number of drops will be added to the sample in Step 3 of
the Test Procedure.
5. Discard this sample.
L Mott