Certainly those with graduate degrees will find the material enriching, but others will find it intimidating. The chemical engineering community will find this book most useful as a reference source or a graduate level text. Reference states, often a confusing topic, receive a clear and concise treat- ment. The text skillfully com- bines classical and statistical thermodynamics (although the coverage of statistical ther- modynamics ignores many topics of current interest). Virtually all important aspects of chemical thermodynamics appear with correct equations. On the positive side, this is an excellent reference text. For example, activity coefficient finds its introduction after all chemical equilibrium and in the last half of the last chapter on phase equilibrium. The most disturbing feature of the text for a chemical engineer is the tortuous path taken to arrive at the practical application rela- tionships for phase equilibrium. Finally, the section on fugacity receives a more- than-cursory treatment, although the subject is still in a very minor role. The sections covering lambda transitions and excess Gibbs energy formu- lations are more nearly up-to-date. Section 1.18 has a clearer explanation of the rela- tionship between molecules and the second law (avoiding the information theory trap this time). The primary changes in this edition are updated references in the footnotes. Those who have copies of the third edition need not rush to purchase this one, however, as most of the changes (which are few in number) are es- sentially cosmetic. This is the fourth edition of a classical text on thermodynamics which has in many ways set the norm for such texts. Denbigh, Cambridge University Press, 1981, 494 pages, $59.50 The Principles of Chemical Equilibrlum, 41h Ed.

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