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1 Overview
Coordination titration is a method of titration analysis using coordination reaction
Coordination reaction is a reaction in which a central ion or atom and a ligand form a coordination bond (coordination ion)
According to the different number of coordinating atoms contained in the ligands, it can be divided into single-base ligands and multi-base ligands, which form simple complexes and chelate complexes with metal ions, respectively
A simple complex refers to a compound formed by direct coordination between a single-base ligand and a central atom
A stable complex formed by a central atom and a multidentate ligand that has a ring structure and clamps the central ion with a double chelate is called an integrant
2.
(1) EDTA and disodium EDTA
When H 4 Y is dissolved in an aqueous solution with high acidity, its two carboxylates can accept H + , so EDTA is equivalent to a hexabasic acid, namely H 6 Y 2+
(2) The stability of EDTA integrants
(3) The acid effect of EDTA
Suppose the total concentration of EDTA is C Y =[Y'], then
The acid effect coefficient is only a function of [H], and has nothing to do with the concentration of the complexing agent.
(4) The lowest pH value and acid effect curve
The calculated minimum pH value required for titration of various ions with EDTA is the ordinate, and lgKMY is the abscissa, and then the acid effect curve is drawn, as shown in Figure 2.
Related Links: Titration Analysis-Precipitation Titration