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8: Gravimetric Methods

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  • Gravimetry includes all analytical methods in which the analytical signal is a measurement of mass or a change in mass. When you step on a scale after exercising you are making, in a sense, a gravimetric determination of your mass. Mass is the most fundamental of all analytical measurements, and gravimetry is unquestionably our oldest quantitative analytical technique. The publication in 1540 of Vannoccio Biringuccio’s Pirotechnia is an early example of applying gravimetry—although not yet known by this name—to the analysis of metals and ores.1 Although gravimetry no longer is the most important analytical method, it continues to find use in specialized applications.

    • 8.1: Overview of Gravimetric Methods
      Before we consider specific gravimetric methods, let’s take a moment to develop a broad survey of gravimetry. Later, as you read through the descriptions of specific gravimetric methods, this survey will help you focus on their similarities instead of their differences. You will find that it is easier to understand a new analytical method when you can see its relationship to other similar methods.
    • 8.2: Precipitation Gravimetry
      In precipitation gravimetry an insoluble compound forms when we add a precipitating reagent, or precipitant, to a solution containing our analyte. In most methods the precipitate is the product of a simple metathesis reaction between the analyte and the precipitant; however, any reaction generating a precipitate can potentially serve as a gravimetric method.
    • 8.3: Volatilization Gravimetry
      A second approach to gravimetry is to thermally or chemically decompose the sample and measure the resulting change in its mass. Alternatively, we can trap and weigh a volatile decomposition product. Because the release of a volatile species is an essential part of these methods, we classify them collectively as volatilization gravimetric methods of analysis.
    • 8.4: Particulate Gravimetry
      Precipitation and volatilization gravimetric methods require that the analyte, or some other species in the sample, participate in a chemical reaction. In a direct precipitation gravimetric analysis, for example, we convert a soluble analyte into an insoluble form that precipitates from solution. In some situations, however, the analyte is already present as in a particulate form that is easy to separate from its liquid, gas, or solid matrix.
    • 8.E: Gravimetric Methods (Exercises)
      These are homework exercises to accompany "Chapter 8: Gravimetric Methods" from Harvey's "Analytical Chemistry 2.0" Textmap.
    • 8.S: Gravimetric Methods (Summary)
      This is a summary to accompany "Chapter 8: Gravimetric Methods" from Harvey's "Analytical Chemistry 2.0" Textmap.

    Thumbnails: An analytical balance (Mettler ae-260) that is often used in gravimetric analysis Methods. Image used with permission (Public Domain; US DEA).