YSI 9300 Photometer - Manual (Page 86)

Reagents and Equipment
YSI DPD No 4 Clear Tablets
YSI DPD Glycine Tablets
YSI 9300 or 9500 Photometer
Round Test Tubes, 10 ml glass (PT 595)
Separation of Ozone Residuals
The photometer is programmed for both ozone and the correction procedure. Use
program Phot 25 Ozone (+Chlorine), then select the ‘Follow On’ option on
screen to continue test using program Phot 26 Correction Procedure. The
corrected ozone residual is calculated automatically and displayed.
Test Procedure
1 Rinse test tube with sample leaving two to three drops of sample in the tube.
2 Add one DPD No 4 tablet, crush tablet and then fill the test tube with sample
to the 10 ml mark. Mix to dissolve tablet.
3 Select Phot 25 on photometer.
4 Take photometer reading in usual manner (see photometer instructions).
5 The result represents the ozone residual as milligrams per litre.
The test may be terminated at this stage for systems treated with ozone alone.
For waters containing both ozone and chlorine or bromine, a correction should be
made as indicated in the following section. Select ‘Follow On’ option on screen to
continue the test program.
Correction for Chlorine or Bromine
1 Fill a test tube with sample to the 10 ml mark. Add one DPD Glycine tablet,
crush and mix to dissolve.
2 Take a second clean test tube and add two to three drops of solution from
the first tube. Add one DPD No 4 tablet, crush and then add the remainder of
the solution to make up to the 10 ml mark. Mix to dissolve tablet.
3 Take photometer reading in the usual manner.
4 The photometer carries out the necessary calculation and displays the
corrected ozone residual as mg/l O
3
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