Principles of Analytical Chemistry

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Books

Principles of Analytical Chemistry Analytical Chemistry, 3rd ed. Douglas A. Skoog and Donald M. West, xii + 685 pages. Holt, Rhinehart & Winston, Inc., 383 Madison Ave., New York, N.Y. 10017. 1979. $17.95 Reviewed by Herbert A. Laitinen, Department of Chemistry, University of Florida, Gainesville, Fla. 32611 This third edition of a well-established text, like the first edition (1965) and the second (1974), is intended for a one-semester course for nonchemistry majors. T h e aim is to cover selected gravimetric and titrimetric procedures with an introduction to some of the basic instrumental measurements used in biological and medical sciences and engineering. Emphasis is on principles rather than on procedures or details. T h e book is designed for flexibility, allowing variations in the order of presentation and the omission of certain portions at the discretion of the instructor. A brief introductory section is presented as a review of principles, mainly stoichiometry and simple equilibrium calculations from general chemistry. Next comes a chapter on evaluation of data, which is intended for presentation when the first laboratory results are submitted. This strikes me as a good idea, especially in these days of the ubiquitous hand calculator when students tend to forget the concept of significant figures. A neat example calculation illustrates the origin of the familiar Gaussian curve for distribution of random errors. At this point, the third edition covers solubility equilibria and gravimetric analysis, followed by titrimetric analysis. Earlier editions had introduced here a section on chemicals, techniques and apparatus; in the third edition this section comes near the end, just before a concluding chapter, "Selected Methods of Analysis." This order of presentation represents a distinct improvement, not only for its logic, but for the psychological impact of stressing principles over routine details. A logical transition from "classical"

to "instrumental" is made through potentiometry and potentiometric titrations, and through electrodeposition and coulometry to polarography and amperometric titrations. T h e discussion of ion-selective electrodes, including solid and liquid membranes and gas-sensing electrodes is especially appropriate for the intended readership. In future editions, it is suggested t h a t enzyme electrodes might be included. The classification of optical methods does not seem entirely logical. A chapter entitled "Absorptiometric Methods of Analysis" includes all regions of the spectrum and perforce includes a section on generation of electromagnetic radiation as well as radiation detectors, which are used both in emission and absorption measurements. T h e other chapter on optical methods is entitled "Atomic Spectroscopy" and includes both emission and absorption methods. Atomic absorption is covered in both chapters. Finally, a chapter on analytical separations includes multiple extraction and chromatographic methods. It is not an easy matter to present analytical principles in an elementary fashion without doing violence to deeper understanding. For the most part, the authors have succeeded admirably, but in a few cases, this reviewer would take exception. On page 276, in discussing the signs of half-cell potentials, the authors state that "the choice as to which potential will be positive and which will be negative is purely arbitrary; however, the sign convention chosen must be used consistently." I would have preferred to say that whether one chooses the sign of the electrical charge on the metal or on the solution side of the double layer is purely arbitrary, but that the IUPAC system chooses the former. It is not arbitrary that zinc metal is negative with respect to hydrogen, and indeed it is this feature that makes the IUPAC system intuitively attractive. Another example is in using the Nernst equation to calculate titration curves even for thermodynamically

unstable and irreversible systems, such as in the region beyond the equivalence point of the permanganate-iron(II) titration. I believe an elementary presentation would be better restricted to reversible systems, or else t h a t further explanation is in order. A relatively minor suggestion is that the use of the symbol e~ rather than e for the electron is an aid in the balancing of half-reactions. Such details aside, this is a book worthy of serious consideration for a one-semester treatment of quantitative analysis for nonchemistry majors. T h e treatment emphasizes fundamentals, presents lots of good chemistry, and offers a selection of important chemical methods as well as an introduction to instrumental measurements.

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