User Guide

20
Note: If the sample is pretreated at the sampling site with the PAO
and the acetate buffer as described before, transfer the sample
quantitatively to the beaker and add one spoon of potassium
iodide from the bottle (HI 70468)
22. Turn on the speed controlled stirrer and
place the beaker on the top of the PL 101.
23.Immerse the probe tip into the sample,
make sure the platinum electrodes are sub-
merged.
24.Dispense the titrant into the beaker in
small increments. Note the reading that
corresponds exactly to the mL of titrant
added. Record at least 3 points before
and 3 points after the End Point.
25.Construct a titration graph.
26.Draw a best-fit line through each set of points. The End
Point is determined
by the intersection of
the two best lines
through the points.
27. Read the volume of
titrant used until the
End Point. This is mL
sample.
28.Calculate the total chlorine concentration using the for-
mula:
4.00 - 4.00 x (mL sample)/(mL zero) = mg/L Total Cl
2
.
Note: If a negative value is found, the sample contains an excess of
de-chlorinating agent, such as sulfur dioxide, sulfite or
bisulfite.