LaMotte Dissolved Oxygen Water Quality - Manual (Page 11)

EPA COMPLIANCE
9
9.
Continue adding Sodium
Thiosulfate, 0.025N until
the blue color disappears
and the solution is
colorless.
10.
Read the test result directly from the scale
where the large ring on the Titrator meets the
Titrator barrel. Include the value of the original
amount dispensed (1 mL). If the reading is 2.0
+/-0.1 mL, the Sodium Thiosulfate, 0.025N
(4169) is satisfactory. If not, discard and
replace with new reagent.
While gently swirling the
tube, add Sodium
Thiosulfate, 0.025N until
the color fades to pale
yellow. It will be
necessary to refill the
Direct Reading Titrator.
7. 8.
Add 3 drops of
Starch
Indicator
Solution
(4170WT).
The solution
will turn blue.
2.0
3.0
Result:
2.0 ppm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0