The distinction between the aliphatic and the aryl free radia l s of Gomberg is so big that the authors confine their brief mention of these latter compounds to the historical treatment which makes up the introduction to the subjeet. In several aspects this book shows a marked parallelism to that of "The Free Energy of Organic Compounds," Parks and Huffman, Chemical Catalog Co , although the two books deal with entirely different, but equally important fundamental fields of chemistry. Both books deal with transformations in the field of organic chemistry; both emphasize pyrogenic reactions (this book more than that of Parks and Huffman): both have a marked similarity in construction: and both are of fundamental importance to the organic chemist. While the one book deals with energy relationships, the other is concerned with the velocities of chemical reactions and the rBle that aliphatic free radicals play in the interpretation of these reactions. Both books deal with chemical "reactivity" but from entirely different points of view. I n this hook one finds complete chapters on the preparation, identification, properties, and reactions of aliphatic free radicals. and a chapter on the activation energies of elementary organic reactions with their interpretation in terms of bond strengths. The later chapters deal with the application of these principles to the pyrogenic reactions of the paraffin hydrocarbons, ketones and aldehydes, olefins, alicyclic compounds, and other compounds of larger and complicated molecules. The last chapter deals with reactions in the liquid phase and the possible place of aliphatic free radicals in the interpretation of these reactions. A valuable table of the activation energies of some 200 reactions constitntes one of the aonendices. .. llesides making a compihtion of the systemalic work that has bwn wnied out in pyrogcnic and rclatcd reactions the authors have made it one of their purposes t o give reasonable mechanisms b y which the products of most pyrogenic reactions can be predicted. Not the least of the authors' purposes has been to point out the possible importance of free radicals as intermediaries in many organic reactions that are now interpreted in other ways. As a textbook this volume can oulv be used advantaewuslv , in more advanced and specializd courses. As a general referrncr book for the chemist the reviewer regards it as one of the noteworthy achievements of chemical litrraturc.
T o continue, "For example, potassium amide, which is a derivative of ammonia in the same sense that potassium hydroxide is a derivative of water, shows all the properties of a base. Acetamidine, as the nitrogen analog of acetic acid, meets our expectations in its behavior as an acetic acid. Acetamide shows the properties of a mixed acetic acid derived simultaneously from water and ammonia. Calcium cyanamid and cslcium cyanate are just as certainly calcium carbonates as is the familiar limestone. The first salt belongs to the nitrogen system, the second is derived a t the same time from ammonia and water, the third belongs to the oxygen system. Acids, bases, and salts, alcohols, aldehydes, and representatives of other classes of compounds containing nitrogen as their dominating element exhibit all the familiar properties of their analogous oxygen compounds." A thorough study of the monograph demonstrates beyond any doubt to the reader that these relationships are not formal in character, but real and significant. Thus a primary amine in ammonia solution exhibits properties which are ch&acteristic of alcohols, and the amidines are really acids. An entirely new point of view is introduced here when one considers the chemistry of these nitrogen compounds in relation to a nitrogen system. I t enables one to predict the behavior of nitrogen compounds from the standpoint of their chemical properties; and it should serve to stimulate, as well as t o guide, investigators in this field. This paint of view alone is an important contribution to chemistry. In the &st chapter of the monograph the physical properties of ammonia solutions are discussed. A few chapters follow dealing with the inorganic nitrogen compounds and nomenclature. The following chapters are concerned chiefly with the chemistry of organic nitrogen compounds. Of especial interest t o the reader are the chapters on the ammono-carbanous. -carbonic, -nitric, and -phosphoric acids. An appendix of more than 20 pages illustrates and describes the manipulations in the handling of liquid ammonia solutions in the laboratory. Frequent references are made t o the literature throughout the monograph. O* CBICAOO TABUNIVBP~LIY c e ~ c m o ILL , WARRENC. JOENSON
TEE POETRYOP MATBEMATICS AND OTAER ESSAYS. David Eugene Smith, Professor Emerituq of Mathematics. Columbia University. Swipta Mathematica'Library, Yeshiva College. New York City, 1934. v 93 pp. 12.5 X 18.5 em. $0.50 in paper, $0.75 in cloth.
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SYSTEM OF COMPOUNDS.Edward Curtk FrankT m NITROGEN lin, Stanford University, California. American Chemical Society Monograph No. 68. Reinhold Publishing Corporation, New York City, 1935. 339, pp. 12 tables. 26 figs. 15.5 X 23 cm. $7.50. Those interested in the chemistry of nitrdgen compounds and, in particular, liquid ammonia solutions have been Looking forward to the appearance of this monograph for many years. An examination of the text reveals that the demands of even the most critical observer have been fulfilled. The monograph represents a scholarly presentation of the results of researches conducted by the author and his students, as well as by workers in other laboratories, in this field during the past forty years. These researches are interpreted on the basis of a nitrogen system of compounds being quite analogous to the mare familiar compounds of the oxygen system. As a solvent ammonia takes the place of water in this system, and the compounds may be regarded as derived from the parent solvent. Thus Franklin states, "Of all known liquids ammonia most closely approaches water in all those properties which give to water its outstanding place among solvents. In its capacity as a solvent for salt liquid ammonia is secondary to water. though some salts, for example the iodides of mercury, lead, and silver, which are insoluble in water, dissolve abundantly in liquid ammonia. It approaches water in its power of ionizing electrolytes. Solutions of salts in liquid ammonia are excellent conductors of electricity. It unites with salts as ammonia of crystallization, ,even surpassing water in its capacity for forming solvates. Like water it is an associated liquid."
It is only fair t o prefacecomment on this Littlevolume of essays with the statement that it suffered the handicap of rather high expectations on the part of the reviewer. The title essay, in particular, elects one phase of a topic In which the reviewer has always felt a warm and sympathetic ihrest-the esthetic aspects of science. Unfortunately, the reviewer's own powers of expression are incommensurate with his capacity far appreciation in this field, and he hopes, all the more eagerly on that account, to find sometime that someone has said well a few of the things which he despairs of saying. One of the paramount difficulties which confronts any commentator on esthetics is that of selecting words which may be used in their dictionary senses or which, indeed, may be used consistently in any one sense throughout the course of a discussion. We have become reconciled to this difficulty in connection with esthetic criticism in music and the graphic arts and t o some extent in literature, and we make concessions to the commentatarconcessions which are often abused to the end that much solemn nonsense is perpetrated and solemnly applauded. As we progress from those branches of esthetics which are predominantly sensory in their appeal toward those whose beauties are purely intellectual, it becomes increasingly more difficult for the commentator to choose his language with precision, and correspondingly more =cult for the reader to overlook or condone errors of choice. The present author has been particularly unfortunate (or misguided) in making the same collection of letters do duty for two different (and sometimes it seems to the reviewer two totally unrelated) ideas. The effect is sometimes as shocking as that of
