Hanna Instruments HI934 Bedienungsanleitung Seite 123

Figure 5 shows the titration of 50 mL of 0.1N NaCl with 0.1N AgNO
and is plotted as pCl (- log [Cl ]).
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2.2.4. COMPLEXOMETRIC TITRATIONS
A complex is a species where a central metal ion is covalently bonded to one or more electron donating groups called ligands.
In a complexometric titration, metal ions are titrated using a titrant that binds strongly to it. Often these titrants contain EDTA
or CDTA, polydentate ligands that form very stable coordination compounds with metal ions. The complexation reaction must
be fast in order to be useful for direct titration. Some metal ions react too slowly with EDTA for a direct titration.
An indicator electrode that responds to the metal ion can be used to monitor the titration progress. The titration curve
will appear similar to a usual potentiometric titration. Complexation indicators change color at the endpoint as all metal
ions are "consumed", or complexed by the titrant.
The titration curve will appear similar to a potentiometric titration, when using an indicator electrode that responds to
the metal ion (see Figure 6).
Figure 5
. The potentiometric signal is from a chloride ISE,
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Figure 6
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