Molecular Thermodynamics; Donald A. McQuarrie and John D. Simon. (1999) University Science Books, 55D Gate Five Road, Sausalito CA 94965, USA. 672 pp $78.00, ISBN 1-891389-05-X

This book is back-to-front - or so it might appear. The harmonic oscillator model of molecular vibration is introduced early in chapter one, molecular partition functions are discussed in chapter three, and symmetry numbers and normal coordinates shortly thereafter. In contrast, such apparently elementary concepts as enthalpy, work, and the First Law make an initial appearance two hundred pages into the book.

To many readers this will seem a very unconventional approach. In chemistry courses, classical thermodynamics is generally studied well before statistical thermodynamics. The latter is mathematically more challenging, and its links to experiment are more difficult to appreciate. Thus, students are often taken first through experimental thermochemical data, and then on to the interpretation of easily recognized observables such as heat and temperature changes; classical thermodynamics is presented as a rationalization of such data. To start with quantum mechanics would be madness, faculty might argue. And yet, it works. There are, of course, solid reasons why this is so. Quantum theory and statistical thermodynamics can indeed form a productive route into classical thermodynamics. Statistical thermodynamics is the more "fundamental" branch of the subject, allowing one to derive the values of macroscopic parameters from the motion and energetics of individual molecules. Indeed, one might argue that one can only really understand thermodynamics as a whole through an appreciation of how changes at the molecular level are responsible for changes in state functions.

The style of Molecular Thermodynamics recalls the authors' successful text Physical Chemistry: A Molecular Approach; indeed, there appears to be significant overlap between the two books. As one delves into Molecular Thermodynamics, the authors' decision to use quantum mechanics as a platform on which to build thermodynamics becomes progressively more understandable and persuasive. The authors address themselves firmly to honours chemists. Only the best students majoring in other subjects will find the book straightforward, even with the help of the inserts that introduce relevant mathematics. However, to the target market of the committed chemist the book has much to offer. The writing is exceptionally clear, and explanations are lucid and sound. Plenty of examples are used to illustrate the arguments, and figures are pertinent. I was a little concerned, however, that a few of the figures might be misleading. For example, in the figures showing the phase diagrams of water and carbon dioxide, the line separating solid and liquid phases is exactly vertical, (though students are warned obliquely in the legend that this is a consequence only of the scales used). Similarly, in the same figures, the lines separating gas from liquid, and gas from solid, are drawn as curves with continuous smooth first derivatives, which is incorrect for these substances. Nevertheless, most diagrams are simple, correct and relevant.

A welcome feature is the use of informative subsection headings. For example:

• 1.1 The Electronic Energy of Atomic Hydrogen is Quantized
• 2.1 All Gases Behave Ideally if they are Sufficiently Dilute
• 6.2 Nonequilibrium Isolated Systems Evolve in a Direction That Increases Their Disorder

This is a simple but effective device that should be used more widely.

This is a chunky book: more than 600 pages on thermodynamics sounds like pretty indigestible stuff, but it is surprisingly palatable. Sales may suffer from the reluctance of students to pay a fairly high price for a book that may appear to deal with only a small section of the syllabus (though the coverage is actually considerably broader than its title might suggest). Although Molecular Thermodynamics may not appear on the shopping list of every chemistry student, it would certainly be a useful addition to the bookshelf of every physical chemistry lecturer.