LaMotte DPD-FAS TITRIMETRIC OUT FIT DT - Manual (Page 8)

3. Use the 100 mL graduated cylinder ((0419) to add 100 mL of
sample water to the flask (0433). Swirl until reagents are dissolved.
Wait 2 minutes. If Total Chlorine is present, solution will turn pink.
4. Use the 1.0 mL pipet (0354) to add 1 mL of *Sulfuric Acid, 5%
(6520) to the solution from the Combined Chlorine test. Mix. Wait
2 minutes.
5. Use the 1.0 mL pipet (0354) to add 5 mL of *Sodium Bicarbonate,
5.5% (6813). Mix.
6. Titrate rapidly with the diluted Ferrous Ammonium Sulfate
Solution. This is Reading D.
CALCULATIONS:
For a 100 mL sample, 1 mL of diluted Ferrous
Ammonium Sulfate equals 1 mg/L Chlorine, ppm Chlorine.
With Calculations as Follows:
In the Case of
Chlorine Dioxide:
Chlorine Dioxide = 5G1
Total ClO
2
Chlorine =
D – C + G2
(this figure should equal
5G1)
Free Chlorine = A – G2
Combined Chlorine = C – A
Chlorite
= D – C – 5G1 + G2
Total Chlorine = D
RESULTS WITH MODIFIED TITRIMETRIC PROCEDURE
The following results were obtained by Dr. A. T. Palin using solutions of
chlorine dioxide in distilled water.
Titrimetric Readings using Modified Procedure
(mg/L as Available Cl
2
)
G1 G2 A C D
0.16 0.16 0.19 0.20 0.82
0.33 0.33 0.46 0.55 1.83
0.54 0.57 0.78 0.86 3.06
0.80 0.97 1.28 1.49 4.69
0.84 0.95 1.30 1.50 4.81
1.22 1.45 1.83 2.02 6.73
The difference between G2 and G1 represents the extent of the errors
in titrations caused by slow color drift-back at end points due to the
slight activation of chlorite in neutral solution. The G readings are now
to be interpreted thus:
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