LaMotte PHOSPHONATE TEST KIT OP-DC - 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:
A.
Fill the test tube (0822) to the 10 mL line with sample water.
B. 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.
C. Add *Hydrochloric Acid (6130) one drop at a time, mixing
between drops. Count the number of drops and continually
compare the color of the sample against the two pH color standards
in the pH Low-High 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.
D. 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. Discard this sample.
L Mott