Manual

Reagents and Equipment
YSI DPD No 1 Tablets
YSI DPD No 3 Tablets
YSI DPD Glycine Tablets
YSI DPD Acidifying Tablets
YSI DPD Neutralizing Tables
YSI 9300 or 9500 Photometer
Round Test Tubes, 10 ml glass (PT 595)
Test Procedures
1 Rinse a clean test tube with sample, then fill with sample to the 10 ml mark.
Add one Glycine tablet, crush and mix to dissolve.
2 Decant two or three drops of Glycine treated sample into a second clean test
tube. Add one DPD No 1 tablet and crush to disintegrate.
3 Add the remaining contents of the first test tube to the second test tube and mix.
4 Select Phot 7 on Photometer.
5 Take photometer reading (Result G) immediately (as result may drift on
standing), in usual manner - see Photometer instructions.
6 Multiply Result G by 5 to obtain the chlorine dioxide residual in terms of mg/;
Chlorine. To obtain the chlorine dioxide residual as mg/l ClO
2
, multiply
Result G by 1.9.
Test Procedures – Free and Combined Chlorine, and Chlorite
1 Rinse a test tube with sample leaving two or three drops. Add one DPD No 1
tablet, crush and then fill the test tube with sample to the 10 ml mark. Mix to
dissolve tablet.
2 Take the photometer reading on Phot 7 immediately (as result may drift on
standing), in usual manner (Result A).
3 Continue the test by adding one DPD No 3 tablet. Crush tablet, mix to dissolve
and then stand for two minutes.
4 Take photometer reading (Result C).
5 Continue the test by adding one DPD Acidifying tablet. Crush tablet, mix to
dissolve and then stand for two minutes.
6 Add one DPD Neutralising tablet, crush and mix to dissolve.
7 Take the photometer reading (Result D).
The results of the tests, in terms of mg/l chlorine, are calculated from the
observed results as follows :
Chlorine Dioxide = 5 x G Free Chlorine = A – G
Combined Chlorine = C – A Chlorite = D – (C + 4G)
Total Oxidizing Capacity = D