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JOURNAL O F CHEMICAL EDUCATION
The fiosl chapter, on chemurgic rtpplicstions of agricultural products (J. R. Clopton), is much too short (11 pages) to cover adequately industrial uses of agricultural products. The elimination of these two chapters from the book would not have materially detracted fromits value. A comparison with the companion Volume I on "P~inciples" reveals a minimum of duplication of materials in spite of the intimate connection between these two books in subject matter. The volume being reviewed suffers, however, in comparison with the former, through s m d , difficult-t+read type used in the makeup of tables. The format of the book otherwise, is excellent. It has been carefully proofread; only one error was noted. This book should fill a long felt need for a general reference text in the field of practioal applications of agricultural chemistry. Its value is enhmced by the bibliographies appended to each chapter.
magnitude which may be stated in terms of m y unit of electricity coulomb, faraday, etc.) which is appropriate. That fact is explained to the student and he is frequently given values of j in coulombs. Each time that j is substituted in an equation, however, it is stated in equivalents, i.e., in fmadays. Only rarely, however, is the conversion factor 5 (coulombs per equivs~ lent) also inserted. The reviewer believea that the student should he shown repestedly that he can rely on obtaining the correct answer in the unit he desires when he writes the units associated with each number introduced into an equation and succeeds in the cancellation of units so as to leave the particular one he wants. Even when the conversion factor 5 is inserted it is called "joules per volt g-eq" rather than coulombs per equivalent (see page 538). The author has missed a rich pedagogical a p portunity; the treatment of units and dimensions deserved more attention in a book of such basic and elementary character. The treatments of methods used for the measurement of surE. A. FIEGER face tension are surprisingly detailed for a text on chemical Lomarax* STAT*UNIYERB~TT thermodynamics. Some of the discussions are better than are BATON ROUGE. Lorns~m~ to be found in most treatises on physical chemistry. The description of the drop weight method, for example, presents the basic principles and the essential details correctly. The attempt 0 EXHIBIT TECHNIQUES to explain the method of maximum bubble pressure is less sucEdited by Helen Miles Davis. Science Service, Washington, cessful. The author explains haw the pressure in a closed system D. C., 1951. ii 112 pp. 26 figs. 1.45 X 20.5 em. Paper, $1; increases as a meniscus is depressed in a capillary by the injection of more and more air. When the line of contact of the doth, $2. meniscus with the wall of the tube reaches the end of the capillary the explanation falters and the hypothetical bubble bursts. The SCIENCE fairs, exhibits, and open-house days require today's science teacher to know more than science. This little book volume of a real bubble continues to increase as more air is forced into it. Simultaneously the pressure continues to increase, supplements a facet of the teacher's versatility. The ways to present a science project to the public are illus- soon reaches a maximum, and then decreases sharply. Not only trated by case histories. We find details about science fairs, is the description of the behavior of the bubble incorrect but it museum methods, and successful projects presented in a way conceals the phenomenon for which the method of "mrtximum that should stimulate the imagination of students and teachers bubble pressure" is named. The selection, at the beginning of alike. I t is a "must" for participants in fairs and science proj- the discussion, of pressure as the independent vmiable made it 0f difficultto discuss pressure as a two-valuedfunotionof the quantity edr4 ..~ ..ftll ~ l k . The hook fulfils its purpose, "to aid teachers and club sponsors of gas in the bubble. Similarly, as a ring is lifted from the surface of a liquid the pull who are asked questions by their students." required rises to a maximum and then decreases. It is this maximum pull which is measured in correct applications of the method. It is themaximum pull which was measured by Harkins, Young, and Cheng, which was discussed explicitly, by Dorsey, which was measured by Harkins and Jordan, and which was calculated by Freud and Freud. Yet the description in "Principles of Chemical Thermodynamics" contains no mention of the 0 PRINCIPLES OF CHEMICAL THERMODYNAMICS m i m u m pull on the ring. The explmation given for the tearMartin A. Paul, Professor of Chemistry, Harpur CoUege, State ing of the ring from the surface is incorrect. The implication University of New York, Endicott, New York. McGraw-Hill Book on page 275 that the method is only a relative one is no longer 740 pp. 64 figs. 61 tahles. true. Since the publication of the Freud and Freud paper the Co., Inc., New York, 1951. viii 15.4 X 23 cm. $7.50. method is-in principle-absolute, Fortunately,the teaching of thermodynamics is not greatly T K I is ~ a large book of more than 700 pages. I t is written in excellent style by an author who is clearly an experienced and affected by these defects in the explanations of methods for painstaking teacher. Typicd of the careful pedagogical planning measurement of surface tension. The reason, of course, is that k the sharp distinction between "molecular weights" and "for- the subject is not essential for the purpose. The reviewer agrees mula weights." Chapter 9 on the Thermodynamics of Cells that surface energy is an excellent example of a free energy and contains many examples of thoughtful pedagogical efforts. that s. discussion of it is appropriate. Methods of measurement, The principles of measurement (but not irrelevant details) however, oould well be omitted from a hook on chemical therare discussed for the benefit of the students for whom the book modynamics and should be omitted unless they can be discussed correctly. was writtm; those who hxvc tnkrn s course or two in physirnl The most serious fault in "Principles of Chemical Themodychrmistry but who h a w studied little or no thermodynxmivs. namics" is lack of attention to mathematical tools--especially rtacro) The clla~ter(72 . . - contain* a scrieaof illuatrat~onaoiactunl investigations of electrical cells. These examples can give the the meaning of partial differentiation and the interrelations of student a notion of some of the practical diioulties encountered partial derivatives. The author is so careless in the handling and may well aid in the development of a critical attitude toward of these subjects that some of his ablest students will be confused. the results of experiment. The associated references may also The reader encounters trouble as early as page 167 where he is serve to show how recently our knowledge of the thermodynamics first introduced to partial molar quantities. He is offered the of solutions was obtained and may lead some students to do following startling definitions of partial molar enthdpies of the respective constituents of a binary solution: ~ufficientlyextensive reading to learn that our present knowledge . is but, an introduction to what lies ahead. (3) and (dH) In this reviewer's opinion there is a serious flaw in Cbaptepter dn, T,p, d m T,p . 9; the treatment of units is not good. The symbol j is used to denote "the quantity of electricity flowing through the cell." The explanation of the subscdpt c is even more amazing; it Like other letter symbols, j represents not a number, but a "denotes that the compositionis regarded asessentially constant.''
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