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9: Titrimetric Methods

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  • Titrimetry, in which volume serves as the analytical signal, made its first appearance as an analytical method in the early eighteenth century. Titrimetric methods were not well received by the analytical chemists of that era because they could not duplicate the accuracy and precision of a gravimetric analysis. Not surprisingly, few standard texts from the 1700s and 1800s include titrimetric methods of analysis.

    Precipitation gravimetry developed as an analytical method without a general theory of precipitation. An empirical relationship between a precipitate’s mass and the mass of analyte—what analytical chemists call a gravimetric factor—was determined experimentally by taking a known mass of analyte through the procedure. Today, we recognize this as an early example of an external standardization. Gravimetric factors were not calculated using the stoichiometry of a precipitation reaction because chemical formulas and atomic weights were not yet available! Unlike gravimetry, the development and acceptance of titrimetry required a deeper understanding of stoichiometry, of thermodynamics, and of chemical equilibria. By the 1900s, the accuracy and precision of titrimetric methods were comparable to that of gravimetric methods, establishing titrimetry as an accepted analytical technique.

    • 9.1: Overview of Titrimetry
      In titrimetry we add a reagent, called the titrant, to a solution containing another reagent, called the titrand, and allow them to react. The type of reaction provides us with a simple way to divide titrimetry into the following four categories: (1) acid–base titrations, (2) complexometric titrations, (3) redox titrations, and (4) precipitation titrations.
    • 9.2: Acid–Base Titrations
      Acid–base titrations, in which an acidic or basic titrant reacts with a titrand that is a base or an acid, is probably the most common titration used by students in laboratories. To understand the relationship between an acid–base titration’s end point and its equivalence point we must know how the pH changes during a titration. We will learn how to calculate a titration curve using the equilibrium calculations from Chapter 6.
    • 9.3: Complexation Titrations
      Complexometric titrations are based on metal–ligand complexation. Practical analytical applications of complexation titrimetry were slow to develop because many metals and ligands form a series of metal–ligand complexes.
    • 9.4: Redox Titrations
      Redox titration are here the titrant is an oxidizing or reducing agent. In contrast to acid/base titrations, it is convenient for redox titrations to monitor the titration reaction’s potential instead of the concentration of one species.
    • 9.5: Precipitation Titrations
      A reaction in which the analyte and titrant form an insoluble precipitate also can serve as the basis for a titration. We call this type of titration a precipitation titration.
    • 9.E: Titrimetric Methods (Exercises)
      These are homework exercises to accompany "Chapter 9: Titrimetric Methods" from Harvey's "Analytical Chemistry 2.0" Textmap.
    • 9.S: Titrimetric Methods (Summary)
      This is a summary to accompany "Chapter 9: Titrimetric Methods" from Harvey's "Analytical Chemistry 2.0" Textmap.

    Thumbnail: A Winkler titration to determine the concentration of dissolved oxygen in a water sample. The dissolved oxygen has been converted to an equivalent amount of iodine, which is being titrated with thiosulfate using a starch indicator. The blue color in the flask will disappear when all the iodine has been converted to iodide. Image used with permission (CC BY-SA 3.0; Will Woodgate (Cornwall College, UK)).