Choice of indicators
Analysis by volumetric procedures requires that some method be employer of indicating the stoichiometric and end point, that is, the equivalence point, of the titration. Internal indicators are greatly preferred. In any event, they should signal the reaching of the completed reaction as closely as possible. Improper choice of indicators can introduce serious errors into volumetric, acid-base, precipitation, adsorption, and oxidation-reduction, all type are used regularly for environmental analysis. Because of the variety, it is ordinarily best to discussed in the following.