Ph-Value With Tablet - Lovibond CheckitDirect Manual De Instrucciones

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Methods
GB

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
0.0.0
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
are aligned.
Zero
Press the [ZERO/TEST] key.
Test
The method symbol flashes for approx. 3 seconds.
PH
The result is shown in the display as pH-value.
RESULT
Tolerance: ± 0,1 pH
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
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
boundary 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
Phenol red
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 %
CheckitDirect_Cl-pH-CyA-TA_2 09/2010
Salt contents
1 molar 2 molar
– 0.21 – 0.26
) may give wrong
3
3 molar
– 0.29
marks
29