YSI 9300 Photometer - Manual (Page 87)

PHOTOMETER TEST INSTRUCTIONS
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pH measurement is one of the tests most frequently carried out on water and
aqueous solutions. The phenol red indicator method provides a simple colori-
metric means of pH determination for neutral and slightly alkaline waters over
the range 6.8 - 8.4 units. The Phenol Red pH test is particularly applicable to
testing swimming pools and spas.
Method
The YSI Phenol Red test uses a tablet reagent containing the precise amount of
phenol red indicator required for the test. Phenol red reacts in water at different
pH values over the range 6.8 - 8.4 to produce a distinctive range of colors from
yellow to red. The color of the test solution is indicative of the pH value and is
measured using a YSI Photometer.
Phenol red tablets contain a dechlorinating agent so that the test can be carried
out in water containing normal levels of chlorine or other disinfectant residuals.
Reagents and Equipment
YSI Phenol Red Clear Tablets
YSI 9300 or 9500 Photometer
Round Test Tubes, 10 ml glass (PT 595)
Test Procedure
1 Fill test tube with sample to the 10 ml mark.
2 Add one Phenol Red tablet, crush and mix to dissolve.
3 Select Phot 27 on photometer.
4 Take photometer reading in usual manner (see photometer instructions).
Photometer Method
AUTOMATIC
WAVELENGTH
SELECTION
6.8 – 8.4
PHOT.27.AUTO