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8: Gravimetric Methods

Last updated

Sep 12, 2021
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- 7.11: Chapter Summary and Key Terms
- 8.1: Overview of 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, in a sense, making a gravimetric determination of your mass. Mass is the most fundamental of all analytical measurements and gravimetry unquestionably is the oldest quantitative analytical technique. Vannoccio Biringuccio’s Pirotechnia, first published in 1540, is an early example of applying gravimetry—although not yet known by this name—to the analysis of metals and ores; the first chapter of Book Three, for example, is entitled “The Method of Assaying the Ores of all Metals in General and in Particular Those That Contain Silver and Gold.” Although gravimetry no longer is the most important analytical method, it continues to find use in specialized applications.

8.1: Overview of Gravimetric Methods
The page provides an overview of gravimetric analysis, which utilizes the measurement of mass as an analytical signal to determine the quantity of an analyte. It discusses methods including direct analysis, where the analyte is weighed directly, and indirect analysis, where the analyte is measured by a change in mass.
8.2: Precipitation Gravimetry
Precipitation gravimetry is an analytical technique where an insoluble compound forms by adding a precipitant to a solution containing the analyte. The precipitate's low solubility, high purity, and known composition are essential for accurate analysis. Minimizing solubility losses and impurities, controlling particle size, filtering, rinsing, drying, and ensuring the precipitate's composition are crucial steps. The technique is reliable but time-consuming, requiring simple equipment.
8.3: Volatilization Gravimetry
Volatilization gravimetric methods involve decomposing a sample thermally or chemically and measuring the resultant change in mass. This approach is essential where a volatile species is released. Thermogravimetry is used to monitor sample mass changes with temperature, aiding in identifying decomposition reactions. Equipment ranges from simple crucibles to complex setups for trapping volatile products.
8.4: Particulate Gravimetry
The page discusses various gravimetric methods, particularly focusing on particulate gravimetry. It covers direct precipitation and the method of separating analytes already in particulate forms using filtration and extraction techniques. Filtration uses different filters based on the particle size, while extraction involves separating analytes from a matrix using a suitable solvent.
8.5: Problems
This page contains a series of complex chemistry problems involving gravimetric analysis, solubility, equilibrium constants, and various chemical reactions. The tasks include verifying equations, constructing solubility diagrams, analyzing chemical precipitates, and determining chemical compositions through specified methods.
8.6: Additional Resources
This page provides a list of references introducing students to the applications of gravimetry through various experiments and historical resources. It includes experiments such as the dehydrochlorination of PVC and gravimetric analysis techniques for nickel, calcium, phosphates, and crude fat. Additionally, it offers resources on the history and methodologies of gravimetry, and a review article on isotope dilution mass spectrometry.
8.7: Chapter Summary and Key Terms
The chapter discusses gravimetric analysis, which involves measuring mass to gain quantitative information about an analyte. It explains precipitation gravimetry, where a reaction creates a precipitate linked to the analyte, and volatilization gravimetry, where decomposition leads to mass measurements of residue or volatilized products. It also touches on particulate gravimetry for direct analysis of analytes in a separable form.

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