Methods
Dissolved Oxygen: Instructions for the use of Hach Kits
Fixing the Sample
1) After putting on gloves and safety glasses, carefully open the envelope marked "Reagent 1"
and add the contents to the bottle. This is the manganous sulfate. Recap the bottle and mix
the contents by turning the bottle over several times.
2) Using similar care, add the contents of the envelope marked "Reagent 2". Recap the bottle
and mix the contents by turning the bottle over several times. This is a combination of lithium
hydroxide, potassium iodide, and azide. A pale precipitate will form.
3) Set the capped bottle aside and wait for the precipitate to settle to the bottom half of the
bottle.
4) Gently mix the solution again, by slowly turning over several times.
5) Wait for the precipitate to settle to the bottom half of the bottle a second time.
6) Carefully open the third reagent package (small plastic tube), and add the contents to
the solution bottle. This is the sulfamic acid.
7) Recap the bottle and gently mix the contents by inverting the bottle several times.
At this point all of the precipitate should dissolve, and if oxygen is present the solution
will turn golden yellow. The sample is now fixed and can be analyzed later.
Analysis of the Sample
1) Wearing gloves and safety glasses, open the sample bottle and fill the small plastic test
tube provided to the top.
2) Empty the test tube into the small clear glass vial provided with your kit. Set the bottle
onto white paper.
3) Using the eye-dropper, add one drop of sodium thiosulfate to the sample and gently shake
the bottle to mix. Note the color of the solution.
4) Continue adding thiosulfate one drop at a time until the yellow color completely disappears.
5) Record the number of drops added to the sample. This is equal to the concentration (in mg/L)
of oxygen originally present in the solution.
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Instructions for the use of LaMotte Kits
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