Theory: and practice

A precipitation gravimetric analysis must have several important attributes. Eirst, the precipitate must be of low solubility, high purity, and of known composition if its mass is to accurately reflect the analyte s mass. Second, the precipitate must be in a form that is easy to separate from the reaction mixture. The theoretical and experimental details of precipitation gravimetry are reviewed in this section. 

Solubility Considerations An accurate precipitation gravimetric method requires that the precipitate s solubility be minimal. Many total analysis techniques can routinely be performed with an accuracy of better than 0.1%. To obtain this level of accuracy, the isolated precipitate must account for at least 99.9% of the analyte. By extending this requirement to 99.99% we ensure that accuracy is not limited by the precipitate s solubility. 

Solubility losses are minimized by carefully controlling the composition of the solution in which the precipitate forms. This, in turn, requires an understanding of the relevant equilibrium reactions affecting the precipitate s solubility. Eor example, Ag+ can be determined gravimetrically by adding Ch as a precipitant, forming a precipitate of AgCl. 

Solubility of AgCI as a function of pCI. The dashed line shows the predicted SAgci, assuming that only reaction 8.1 and equation 8.2 affect the solubility of AgCI. The solid line is calculated using equation 8.7, and includes the effect of reactions 8.3-8.5. A ladder diagram for the AgCI complexation equilibria is superimposed on the pCI axis. 

If this is the only reaction considered, we would falsely conclude that the precipitate s solubility, SAgcb is given by 

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L. Ljung, T. Sbderstrbm, Theory and Practice of Recursive Identification, MIT Press, Cambridge, MA, 1983... 

Industrial Radiology, Theory and Practice, R. Halmshaw, Applied Science Publshers, London, 1982... 

Development of Theory and Practice of Liquid Penetrant Testing. 

A. L. Smith, Ed., Theory and Practice of Emulsion Technology, Society of Chemical Industry, London, 1976. 

Tang J and Albrecht A C 1970 Developments in the theories of vibrational Raman intensities Raman Spectroscopy Theory and Practice vol 2, ed H A Szymanski (New York Plenum) pp 33-68... 

Dayie K T, Wagner G and Lefeevre J F 1996 Theory and practice of nuclear spin relaxation in proteins Anna. Rev. Phys. Chem. 47 243-82... 

Weii J A, Boiton J R and Wertz J E 1994 Electron Paramagnetic Resonance Elementary Theory and Practical Applications (New York Wiiey)... 

Moor H 1987 Theory and practice of high pressure freezing Cryotechniques in Bioiogicai Eiectron Microscopy ed R A Steinbrecht and K Zieroid (Beriin Springer) pp 175-91... 

Clayton C R and Olefjord I 1995 Corrosion Mechanisms In Theory and Practice ed P Marcus and J Oudar (New York Dekker) p 175... 

Baeckman W v, Schenk W and Prinz W 1997 Handbook of Cathodic Corrosion Protection Theory and Practice of Electrochemical Protection Processes (Flouston, TX Gulf)... 

Ashworth V and Booker C J L (eds) 1985 Cathodic Protection Theory and Practice (New York Ellis Norwood)... 

Riggs O L and Locke C E 1981 Anodic Protection Theory and Practice in the Prevention of Corrosion (New York Plenum)... 

Being able to ntn direct dynamics calculations will add an extra, important, tool to help chemists understand photochemical systems. This chapter has outlined the present standpoint of the theory and practice of such calculations showing that, although much work remains to be done, they are already bringing new insight to mechanistic studies of photochemistry. 

A method for determining the SO, content of oleum is described in the author s Text Book 0/ Quantitative Inorganic Analysis Theory and Practice, Second Edition, 1951, p. 263 (Longmans, Green and Co. Ltd.). 

Bates, Determination of pH, Theory and Practice, Wiley, New York, 1964, pp. 121-122. t Elving, Markowitz, and Rosenthal, Awfl/. Chem., 28 1179 (1956). 

Isotherms of the type now characterized as Type IV have played an essential part in the development of adsorption theory and practice, as being the first kind of isotherm to be studied in detail. Already in 1888, half a century before the BDDT classification had appeared, van Bemmelen had... 

Gurrie, L. A., ed. Detection in Analytical Chemistry Importance, Theory and Practice. American Ghemical Society Washington, DG, 1988. 

Gy, P. M. Sampling of Particulate Materials Theory and Practice Elsevier Amsterdam, 1979. 

Pawliszyn, J. Solid-Phase Microextraction Theory and Practice, Wiley NewYork, 1997. 

Source Values taken from Bates, R. G. Determination of pH Theory and Practice, 2nd ed. Wiley New York, 1973. Concentrations are given in molality (moles solute per kilograms solvent). 

For a description of electrogravimetry, see the following resource. Tanaka, N. Electrodeposition, In Kolthoff, I. M. Living, P. J., eds. Treatise on Analytical Chemistry, Part I Theory and Practice, Vol. 4. Interscience New York, 1963. 

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