tion of acetaldehyde and acetic acid from acetylene.

It is impossible for the reviewer to ex- press anything but admiration for this work because of its very complete and remarkably well-balanced treatment of almost all of the phases of our knowledge of organic chemistry.

FRANK C. WHSCMORB '

Catalysis in Theory and Practice. E. K. RIDEAL AND H. S. TAYLOR. Macmillan and Co., Ltd., New York City. Second edition, 1926. xv + 516 pp. 13.5 X 21.5 cm. $6.00 net.

Any user of the first edition of this important work knows intuitively that he must have a copy of the second edition. The rapid advances in our knowledge of catalysis since 1919 insure that the new edition cannot help but be greatly im- proved.

Drs. Rideal and Taylor have taken full advantage of their opportunity. The whole work has been completely revised, rearranged, and expanded. Three chap- t e n have been added and the text of the book enlarged altogether by about thirty- five per cent. Although only twenty pages have been added, this has become possible through the use of smaller type Chapters II-Theoretical Iutmduction- and III-The Measurement of Reaction Velocity in Catalytic Processes--of the older edition have been expanded so as to cover Chapters I1 to VI in this edition. The titles of these chapten are Criteria of Catalysis; Homogeneous Reactions; The Theory of Heterogeneous Catalytic Re- actions; Promoters; Mixed, Supported, and Protected Catalysts; Catalyst Poisons; and the Inhibition of Homogeneous Chemical Reactions.

This serves to show where the growth of our knowledge of catalysis has occurred. The theoretical part of the book has, in consequence, been enormously improved. The concept of active moledes and re- lated topics has been expanded from three to twenty pages, the properties and he-

haviar of solid catalytic agents from ten to thirty-two pages, and negative catalysis from one and one-half to fifteen pages. There is a section showing the correlation of the data of catalysis with the thermo- dynamic properties of solutions, a section discussing the structure and probable mode of formation of unstable complexes, and a section going very thoroughly into the subject of promoters and promoter action.

But it is not the theoretical part alone that shows improvement. Many new processes are recorded and described. Notable among these are the new processes for synthetic methanol and for synthetic motor fuels. The Claude, high- pressure process for nitrogen fixation is discussed. The chapter on Catalysis by Radiant Energy has been expanded fifty per cent.

The book is replete with references. Although the authors disclaim any attempt a t bibliography compilation, one cannot help but feel that they have included enough. The paper, binding and printing are a decided improvement over the first edition. Catalysis in Theory and Prac- tice is without doubt destined to stimulate very greatly our interest in and investiga- tion of that subject.

MALCOLM M. HARWO

Equilibria in Saturated Salt Solutions. W. C. BLASDALE. A. C. S. Monograph Series. The Chemical Catalog Co., Inc., New York City, 1927. 197 pp. 15 X 22.5 cm. $4.50 net.

This book is a summary of studies made over a long period of years by many people on saturated aqueous salt solutions. It does not attempt to cover all the data available, nor is i t a compendium of liter- ature references. Only the more impor- tant systems are considered. Nevertheless it should prove an invaluable aid to every worker in this field.

Although this monograph covers all twes of salt solutions from 2 to 6 comDo- . . nents, its greatest duel ies in thetr&tment

of 3.4.5. and 6 component systems. This is really excellent. The discussion of P-T diagrams for binary salt solutions is very good and more extensive than one usually finds in the standard works on the phase rule. One wonders why the first chapter on the system water is included a t all. Use of Dr. Blasdale's work pre- s~pposes a thorough knowledge of the first principles of phase theory, and this chapter does not seem to add to it.

Especially commendable are the very thorough discussions of the various graph- ical methods in use to represent poly- component systems; the excellent review of the problem of the Stassfurt salt de- posits; and the many illustrations of the calculations of heterogeneous equilihrium. For example, there is a discussion of the use of phase diagrams in quantitative calculations, of calculations on four component systems, and of the changes occurring during the evaporation of sea water.

On page 47, Ahbegg should he changed to Abegg, and on pages 50, 52 and 53, the correct reference is Carpenter and Jette rather than Carpenter and Jelle. The equilibrium signs on page 50 and else- where should be * rather than -+. Aside from these points, the cuts, binding, printing, etc., are done in the excellent style of the other A. C. S. monographs. Altogether Dr. Blasdale is to be congratu- lated on his contribution to this valuable series.

MALCOLM M. HARING

Physico-Chemical Metamorphosis, and Some Problems in Piezo-Chemistry. ERNST cone^. McGraw-Hill Book Company, Inc., New York City, 1926. 190 pp. 15 X 23 cm. $2.50.

Dr. Ernst Coheu, University of Utrecht, is well-known in the United States not only through his great professional and scien- tific reputation hut also because of the charm of his personality and his ability to entertain his audiences. It is, therefore,

with a great deal of pleasure that we see the publication of Dr. Cohen's lectures a t Cornell University.

These lectures cover two subjects, one, physico-chemical metamorphosis, and the other piezo-chemistry. The text was originally written by Dr. Cohen in German and has been admirably translated into English by Dr. I,. F. ~udreith.

Dr. Cohen in the f i s t half of his hook brings out clearly an unappreciated fact; to wit, that most solid substances, elements, or compounds are capable of existing in two or more physical forms. This is brought out by numerous experimental investigations on various substances by the author and his co-work- ers. As he states, the importance of this fact is considerable if &takes into con- sideration that each physical type has its own physical properties and. therefore, many of the physical measurements whose results are shown in the handbooks and in the general literature are highly in error because they fail to state which physical form was tested. Discrepancies in re- parted results of physical measurements may be largely attributed to this cause. Not only is i t possible that separate in- vestigators used different physical types of the same substance but i t is also proh- able that may of them worked with mix- tures rather than with single pure physical types.

The reviewer would like to point out that i t is quite possible that future genera- tions of Cohens will discover that each physical form is capable of being separated into sub-physical forms which we will call for the moment "isotopes." For example, the alpha form of cadmium iodide will be found to have 42 sub-physical "isotopes" and after ten years of experimentation it will be possible to separate only one of the 42, number 23, in concentrations up to about 40%. In other words, without wishing to appear factitious, the broad idea of subdivision will go on indefinitely and from a philosophic standpoint there is no limit. Dr. Cohen, however, should be congratulated on his dear and fascinating