Kinds of Titration

Updated July 20, 2017

Titration is a procedure used to determine the amount of reactant present in a chemical solution; it is used to cause a reaction in such a way that the reactant is not in excess. The process of titration involves carefully adding a solution in a standard, known concentration, using a burette (or burette), to the reactant. An indicator is then used to determine the endpoint of the reaction. There are many different types of titration, but the principal methods are acid-base, redox, complexometric and zeta-potential titrations.

Acid-Base Titration

Acid-base titration is the most commonly used titration. Depending on the solution that is undergoing titration, acid-base titration is used to form a neutralisation reaction until completion; that is, if the sample solution is acidic, the known, standardised solution added to the sample solution will be basic. At the point of completion, an equivalence point is found at which equal amounts of acid and base are present in the solution. The most common indicator used in acid-base titration is phenolphthalein, which changes the colour of the solution from colourless to magenta when the point of equivalence is reached.

Redox Titration

Redox (or reduction-oxidation) titration relies on the oxidation of the reactant; the known standard solution used in a redox titration is usually an oxidising agent such as permanganate ion (MnO4-) or dichromate ion (Cr2O72). These oxidising agents can be used as indicators for the reaction, as the reduced permanganate ions will turn from purple to colourless, and orange dichromate ions will turn green when reduced. The titration curve produced to determine the endpoint is formed by mapping the amount of electrode potential against the volume of the solution.

Complexometric Titration

In this process a coloured complex is used as an indicator to determine if there are different types of metal ions in the solution. EDTA (ethylenediaminetetraacetic acid) is commonly used for complexometric titration. EDTA can act as a Lewis base, but is primarily used in the reaction to form EDTA-metal ion complexes, since it is assumed that the formation of these complexes will drive the reaction to completion.

Organic indicators are mainly used in this titration process.

Zeta Potential Titration

Zeta potential titration is the process of titrating heterogeneous systems, such as colloids. There are high surface areas of solids in these systems, which is the main basis of study in a zeta potential titration. Different properties can be studied from the surface areas of the solids, such as the determining the isoelectric point and the optimum dose of surfactant that will achieve stabilisation. The titration indicator is the zeta potential, which can be calculated by microelectrophoresis, electrophoretic light scattering or electroacoustic phenomena.

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