User Guide

16
8. Dispense the titrant into the beaker in
small increments. Note the downward
reading on the amperometric titrator.
Record the display reading that corre-
sponds exactly to the mL of the titrant
added. Record at least 3 points before and
3 points after the End Point.
9. Construct a titration graph using the PL 100 graph paper.
10.Draw the best-fit line
through each set of
points. The end
point is determined
by the intersection of
the two best lines
through the points.
11.Read directly the free chlorine concentration on the
top of the graph by drawing a straight vertical line through
the End Point or read the volume of titrant used until the
End Point and multiply by 2 when titrant (a) 0.00564N
PAO is used or multiply by 0.2 when titrant (b) 0.000564N
PAO is used.
mL
(till End Point)
x 2
(or 0.2)
= mg/L Free Cl
2
.
Method B: Total Chlorine Forward Titration (PL 101 only)
1. Fill the bottle of the automatic burette with
0.000564N PAO solution (HI 70471)
for titrations up to 1500µg/L Cl
2
or use
the 0.00564N PAO solution (HI 70466)
for titrations up to 15000µg/L Cl
2
. Fill the
10 mL automatic burette to the zero mark.
2. Use a 100 mL volumetric pipet to transfer 100mL of sample
to a 250 mL beaker and add about 100 mL chlorine free
water.
3. Add one spoon of potassium iodide from the bottle (HI
70468) and swirl to dissolve. Place the stirbar into the
beaker.
4. Add 1 mL of pH 4 acetate buffer solution
(HI 70467) into the beaker.
5. Turn on the speed controlled stirrer and
place the beaker on the top of the PL 101.