ABSTRACT
For titration of a metal ion with a complexing ligand, the formation constant of the complex must be large so that the titration reaction will be stoichiometric and quantitative. A variety of substances, often called metallochromic indicators, are available for this titration procedure. The most common indicator used in complexometric titration is Eriochrom Black T. Titration with standard EDTA is used throughout most of the world to determine the amount of hardness in water. The development of modern analytical methods such as spectroscopy has somewhat reduced dependence on oxidation-reduction titrations for inorganic analysis. Direct iodine titrations are usually carried out in neutral or acidic solution. At pH value higher than 11, the stoichiometry of iodine titrations is erratic. Direct iodine titration is the Karl Fisher method for water.
