LaMotte AG-104 Salt Water Aquarium - Manual (Page 10)

“Fix ing” the Wa ter Sam ple
NOTE:
Be careful not to introduce air into the sample while adding
the reagents in Steps 5 and 6. Drop the reagents into the test sample,
cap carefully, and mix gently.
5. Add 8 drops of *Manganous Sulfate Solution (4167) and 8 drops of
*Alkaline Potassium Iodide Azide Solution (7166). Cap and mix by
inverting gently several times. A precipitate will form. Allow the
precipitate to settle below the shoulder of the bottle before
proceeding.
6. Add 8 drops of *Sulfuric Acid, 1:1 (6141WT). Cap and gently
invert to mix, until both the reagent and the precipitate have
dissolved. A clear yellow to brown-orange color will develop,
depending on the oxygen content of the sample.
NOTE:
Following the completion of Step 6, contact between the
water sample and the atmosphere will not affect the test result.
Once the sample has been “fixed” in this manner, it is not necessary
to perform the actual test procedure immediately.
Test Pro ce dure
1. Fill the test tube (0608) to the 20 mL line with the “fixed” sample.
Cap.
NOTE:
If the color of the “fixed” sample is already a very faint
yellow, skip Step 3, perform Step 4, and begin the titration at
Step 5.
2. Fill the DRT (0377) with *Sodium Thiosulfate Solution (4169).
Insert into the center hole of the test tube cap.
3. While gently mixing the tube, slowly press the plunger to titrate
until the yellow-brown color is reduced to a very faint yellow.
4. Remove the Titrator and cap. Be careful not to disturb the Titrator
plunger, as the titration begun in Step 3 will be continued in
Step 5. Add 8 drops of Starch Indicator Solution (4170WT).
Solution will turn blue.
5. Replace the cap and Titrator and continue titrating until the blue
color just disappears. Read result directly from the scale where the
large ring on the Titrator meets the Titrator barrel. Record as ppm
Dissolved Oxygen. Each minor division equals 0.2 ppm.
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