46
WT.050.311.000.DM.IM.0119
P7
Advanced
pH-value with Tablet
6.5 – 8.4
Fill a clean vial (24 mm Ø) with
10 ml of the water sample
and
perform zero calibration (see “Operation").
Add
one PHENOL RED PHOTOMETER tablet
straight from the foil to
the 10 ml water sample and crush the tablet using a clean stirring rod.
Close the vial tightly with the cap and swirl gently several times until
the tablet is dissolved.
Place the vial in the sample chamber making sure that the marks
are aligned.
Press the [ZERO/TEST] key.
The method symbol flashes for approx. 3 seconds.
The result is shown in the display as pH-value.
Tolerance:
± 0.1 pH
0.0.0
PH
Zero
Test
RESULT
Notes:
1. For photometric determination of pH-values only use PHENOL RED tablets in black
printed foil pack and marked with PHOTOMETER.
2. Water samples with low values of Alkalinity-m (below 35 mg/l CaCO
3
) may give wrong
pH readings.
3. pH-values below 6.5 and above 8.4 can produce results inside the measuring range.
A plausibility test (pH-meter) is recommended.
4. The accuracy of the colorimetric determination of pH-values depends on various bound-
ary conditions (buffer capacity of the sample, salt contents etc.).
5. Salt error
Correction of test results (average values) for samples with salt contents of:
Indicator
Salt contents
Phenol red
1 molar
– 0.21
2 molar
– 0.26
3 molar
– 0.29
The values of Parson and Douglas (1926) are based on the use of Clark and Lubs buffers.
1 Mol NaCl = 58.4 g/l = 5.8 %
PH
Methods
English
Содержание WALLACE & TIERNAN P7 ADVANCED
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