8.S: Gravimetric Methods (Summary)

In a gravimetric analysis, a measurement of mass or a change in mass provides quantitative information about the analyte. The most common form of gravimetry uses a precipitation reaction to generate a product whose mass is proportional to the amount of analyte. In many cases the precipitate includes the analyte; however, an indirect analysis in which the analyte causes the precipitation of another compound also is possible. Precipitation gravimetric procedures must be carefully controlled to produce precipitates that are easy to filter, free from impurities, and of known stoichiometry.

In volatilization gravimetry, thermal or chemical energy decomposes the sample containing the analyte. The mass of residue remaining after decomposition, the mass of volatile products collected with a suitable trap, or a change in mass due to the loss of volatile material are all gravimetric measurements.

When the analyte is already present in a particulate form that is easy to separate from its matrix, then a particulate gravimetric analysis may be feasible. Examples include the determination of dissolved solids and the determination of fat in foods.

8.5.1 Key Terms

coagulation conservation of mass coprecipitate definitive technique digestion direct analysis electrogravimetry gravimetry homogeneous precipitation

ignition inclusion indirect analysis occlusion particulate gravimetry peptization precipitant precipitation gravimetry

quartz crystal microbalance relative supersaturation reprecipitation supernatant surface adsorbate thermogram thermogravimetry volatilization gravimetry

References

1. Smith, C. S.; Gnodi, M. T. translation of Biringuccio, V. Pirotechnia, MIT Press: Cambridge, MA, 1959.
2. Valacárcel, M.; Ríos, A. Analyst 1995, 120, 2291–2297.
3. (a) Moody, J. R.; Epstein, M. S. Spectrochim. Acta 1991, 46B, 1571–1575; (b) Epstein, M. S. Spectrochim. Acta 1991, 46B, 1583–1591.
4. Von Weimarn, P. P. Chem. Revs. 1925, 2, 217–242.
5. Bassett, J.; Denney, R. C.; Jeffery, G. H. Mendham. J. Vogel’s Textbook of Quantitative Inorganic Analysis, Longman: London, 4th Ed., 1981, p. 408.
6. Gordon, L.; Salutsky, M. L.; Willard, H. H. Precipitation from Homogeneous Solution, Wiley: NY, 1959.
7. Ward, R., ed., Non-Stoichiometric Compounds (Ad. Chem. Ser. 39), American Chemical Society: Washington, D. C., 1963.
8. Method 4500-SO₄^2– C and Method 4500-SO₄^2– D as published in Standard Methods for the Examination of Waters and Wastewaters, 20th Ed., American Public Health Association: Washington, D. C., 1998.
9. Jungreis, E. Spot Test Analysis; 2nd Ed., Wiley: New York, 1997.
10. (a) Ward, M. D.; Buttry, D. A. Science 1990, 249, 1000–1007; (b) Grate, J. W.; Martin, S. J. ; White, R. M. Anal. Chem. 1993, 65, 940A–948A; (c) Grate, J. W.; Martin, S. J. ; White, R. M. Anal. Chem. 1993, 65, 987A–996A.
11. Muratsugu, M.; Ohta, F.; Miya, Y.; Hosokawa, T.; Kurosawa, S.; Kamo, N.; Ikeda, H. Anal. Chem. 1993, 65, 2933–2937.
12. Sinha, S. K.; Shome, S. C. Anal. Chim. Acta 1960, 24, 33–36.
13. Adapted from Sorum, C. H.; Lagowski, J. J. Introduction to Semimicro Qualitative Analysis, Prentice-Hall: Englewood Cliffs, N. J., 5th Ed., 1977, p. 285.
14. Grote, F. Z. Anal. Chem. 1941, 122, 395–398.
15. Nawrocki, J.; Carr, P. W.; Annen, M. J.; Froelicher, S. Anal. Chim. Acta 1996, 327, 261–266.
16. Fat Determination by SFE, ISCO, Inc. Lincoln, NE.
17. Delumyea, R. D.; McCleary, D. L. J. Chem. Educ. 1993, 70, 172–173.18 Yao, S. F.; He, F. J. Nie, L. H. Anal. Chim. Acta 1992, 268, 311–314.

Contributors

• David Harvey (DePauw University)