Gravimetry is the quantitative measurement of an analyte by weighing a pure, solid form of the analyte. Obtaining pure solids from solutions containing an unknown amount of a metal ion is done by precipitation.
Since gravimetric analysis is an absolute measurement, it is a principal method for analyzing and preparing primary standards. A typical experimental procedure to determine an unknown concentration of an analyte in solution is as follows:
- quantitatively precipitate the analyte from solution
- collect the precipitate by filtering and wash it to remove impurities
- dry the solid in an oven to remove solvent
- weigh the solid on an analytical balance
- calculate the analyte concentration in the original solution based on the weight of the precipitate
Examples of Gravimetric Lab Procedures
Gravimetric Determination of Iron
- Determine constant weight of the crucibles
- Oxidation of iron sample
- Precipitation of iron hydroxide
- Ignition of iron hydroxide to iron oxide
- Determine constant weight of the crucibles plus iron oxide
- Calculation of iron in the sample
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