LaMotte DISSOLVED OXYGEN TEST KIT - Manual (Page 4)

TITRATION
1.
Fill the test tube (0608) to the 20 mL line with the “fixed” sample
and cap.
NOTE:
For more precise oxygen measurements, fill graduated
cylinder (2-2297) to 20 mL line with sample. Transfer to test tube
(0608). Cap.
2. Fill the Direct Reading Titrator (0377) with *Sodium Thiosulfate,
0.025N (4169).
3. Insert the Titrator into the center hole of the test tube cap. While
gently shaking the tube, slowly press the plunger to titrate until the
yellow-brown color is reduced to a very faint yellow.
NOTE:
If the color of the “fixed” sample is already a very faint
yellow, skip to Step 4.
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). Sample
should turn blue.
5. Replace the cap and Titrator. Continue titrating until the blue
color just disappears. Read the test result directly from the scale
where the large ring on the Titrator meets the Titrator barrel.
Record as ppm dissolved oxygen.
NOTE:
Each minor division on the Titrator scale equals 0.2 ppm.
6. If the plunger tip reaches the bottom line on the Titrator scale
(10 ppm) before the endpoint color change occurs, refill the
Titrator and continue the titration. When recording the test result,
be sure to include the value of the original amount of reagent
dispensed (10 ppm).
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