Complex-formation titrations endpoint detection

In some complex-formation titrations, the endpoint is noted by the formation or disappearance of a solid phase. For example, in the titration of cyanide with silver ion, the solution remains clear, but the first excess of silver causes formation of a white solid that marks the endpoint. The electron-donor groups of most common ligands tend to combine not only with metallic ions but also with protons thus, the equivalence point in a complex-formation titration is often accompanied by a marked change in pH, which can be detected with an acid-base indicator. 

According to the type of chemical reaction used, methods based on the formation of precipitates and methods based on complex formation can be distinguished. Because of the necessity for handling precipitates, precipitation radiometric titrations are difficult to apply to less than milligram amounts and. therefore, have no special advantages over other volumetric methods. The sensitivity of complexometric titrations is limited by the sensitivity of the determination of the endpoint. However, the use of radiometric detection can substantially increase the sensitivity of this type of determination. For the separation of the product from the initial component, liquid-liquid distribution, ion-exchange, electrophoresis, or paper chromatography are most often used [2]. [63], [88], [93], [97]. 

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