Maintenance
79
Alkaline Error
High concentrations of sodium ions interfere with readings in alkaline
solutions. The pH at which the interference starts to be signicant depends
upon the composition of the glass. This interference is called alkaline error
and causes the pH to be underestimated. Hanna’s glass formulations have the
indicated characteristics.
Sodium Ion Correction for the glass at ambient temperature
Concentration pH Error
0.1 mol/L
Na
+
12.5 0.05
13.0 0.11
13.5 0.16
14.0 0.20
1.0 mol/L Na
+
11.5 0.01
12.0 0.06
12.5 0.11
13.0 0.15
13.5 0.21
14.0 0.27
Rinse the probe with clean water after measurements. If a more thorough
cleaning is required, remove the probe sleeve and clean the probe with a cloth
or a nonabrasive detergent. Make sure to reinsert the sleeve onto the probe
properly and in the right direction. After cleaning the probe, recalibrate the
instrument.
The insulator used to support the platinum rings is made of glass. Use extreme
caution when handling this probe.
EC Probe
Maintenance
pH Probe
Maintenance
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