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NEW BOOKS B y F. H. MacDougall. 22X 15 CVL; New York: John Wiley and Sons, 1921. Price: $5.5o.-In the

Thermodynamics and Chemistry.

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+ 391.

preface the author says: “No one can write on thermodynamics without being deeply influenced by Willard Gibbs and Max Planck. The writings of the former will always be the admiration (and sometimes the despair) of the student of thermodynamics on account of the extreme rigor and completeness with which he discusses the subject, while Planck in his Lectures on Thermodynamics has given a treatment which is a model of conciseness, accuracy and logic. It has been my endeavor to write a book which, in addition to being accurate, logical and sufficiently rigorous, will furnish the student with numerous examples of the application of the principles of the science. It is with this object in view that four chapters have been devoted to the phase rule and its applications.” “This book has been written to meet the needs of advanced students of Chemistry. While a course in thermodynamics is indispensable to students of physical chemistry it is no less desirable for the organic chemist, who finds that, to an ever increasing degree, he must make use of physico-chemical methods and laws, the full significance of which will hardly be clear to one who is not familiar with their thermodynamic foundations. Moreover, the instructor in general of analytical chemistry, if he is not already acquainted with the principles of thermodynamics, will find that a knowledge of them will be of great service to him, both in the class-room and in the laboratory. Many of the laws which we meet with in text-books of Chemistry are valid only under certain definite conditions. Chemical literature is full of instances in which writers have employed these laws in cases in which they are no longer valid. An exact knowledge of the conditions under which these laws may be applied would have prevented this waste of time and energy.” The subject is presented under the following heads: temperature; actual gases; heat; the first law of thermodynamics; applications of the first laws; thermochemistry; the second law of thermodynamics ; deductions from the first and second laws ; thermodynamic functions and thermodynamic equilibrium; fusion; evaporation, and sublimation; the phase rule; applications of the phase rule; chemical equilibrium; chemical equilibrium in liquid solutions; electromotive force; surface tension and adsorption; radiation, quantum theory, Nernst heat theorem. This is a perfectly good book and the author has done what he tried to do, except that he has left out Storch’s formula on p. 296 and that he states on p. 344 that we only measure adsorption because we cannot measure the surface tension of solids. The point that interests the teacher of chemistry is not whether this or any similar book is good of its kind; but whether it is the kind of book that is good for the student. On this great question the reviewer admits that he is an extremist and that his opinion is not that of the majority. The modern thermodynamical chemist appears to be a purely formal creature who writes pages of formulas instead of putting the subject clearly in relatively few words. To men like the author thermodynamics is an end in itself. To the reviewer thermo-

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dynamics should be an instrument of research. We have had a good. many years of thermodynamical chemistry in America and it seems to the reviewer that the results obtained in the last quarter-century are pitifully scanty although the gross output is enormous. Old results have been rewritten and new terms have been coined; but that is not what the reviewer wants. We do not know anything quantitative about the relation between the heat of dilution and apparent osmotic pressure a t constant temperature. In our so-called rigorous thermodynamical relations for the distribution law, we ignore the changing miscibility of the two solvents. We write equations for the chemical potentials; but we do not deduce a theoretical formula for the dineric equilibrium between benzene, alcohol, and water to take the simplest experimental case. We use Henry’s law for one component and the relation is specific. We use the van’t Hoff-Raoult formula for the other component and the relation is general. The thermodynamical formulas for the partial pressures of mixtures of two liquids contain no term for the molecular weights in the liquid phase. We treat a dissolved substance exclusively as a gas even though we know that in most respects it behaves like a liquid. That precludes any adequate discussion of the Soret phenomenon. We do not discuss the question whether there is a real difference between solvent and solute because we put in the definition that the solute is the substance which does not pass through the semipermeable membrane which is not there. When this fails us, as in three-component systems, we speak qualitatively of thermodynamic environment and let it go a t that. We know that the Gibbs formula for the lowering of surface tension applies only to true solutions and we proceed to apply it to colloidal solutions. We find experimentally that certain colloidal solutions do show marked surface concentrations; but we turn in vain to the mathematical chemist for a quantitative or a qualitative explanation. This sort of definite criticism might be continued indefinitely. Thermodynamics should be a most important and valuable instrument of research; but the only possible reason today for urging a chemist to study thermodynamics is that we may some day find a man who can learn to handle his thermodynamics without losing his creative instincts. There have been such men. Van’t Hoff was one, and the modern mathematical chemist speaks of him pityingly as not being very strong in thermodynamics. That is true; but van’t Hoff knew that one must feed ideas into the thermodynamical machine if one is to get new results out of it. The men who improve on him have forgotten this essential point. This screed is not directed against Mr. MacDougall’s book but rather against the whole group of books of which this is merely one. One may however criticize the author legitimately for the way in which he has side-stepped the w7ho.e question of the degree of ionization. He not only does not commit himself a t all; but he does not even tell the student that it is a vital problem. On p. 284 he says that in all methods of determining the degree of ionization “the correct interpretation of the results is conditioned by correct assumptions as to the nature of the substances present in the solution.” On p. 286 he says that “if we assume that the degree of ionization of a solution of a binary electrolyte is given accurately by the relation . . . . .” That is hardly the accurate, logical and sufficiently rigorous application of the principles of science which we were

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promised in the preface. The joke-or the sad part-of the thing is that the author has an improved dilution law and is therefore tremendously interested Wilder D . Bancroft in the degree of ionization. Relativity, the Electron Theory and Gravitation. B y E . Cunningham. Second edition. 22 X 15 cm; p p . vii 148. New York; Longmans, Green and Co., 1921. Pricf: $3.5o.-In the preface t o the first edition (1916) the author says that the monograph is an attempt to set out as clearly and simply as possible the relation of the Principle of Relativity to the generally accepted Electron Theory, showing a t what points the former is the natural and necessary complement of the latter. I n the preface to the second edition (1920) he says: “The first edition of this book was published while the General Principle of Relativity was being worked out, before i t seemed possible to arrive a t any confirmation from observation. Shortly after, however, i t was shown that the new Theory explained the motion of the perihelion of Mercury, and now the result of the Solar Eclipse expedition has clinched matters.” The book is divided into two parts, the first dealing with the special principle, and the second with the general principle of relativity. I n the first part the chapters are entitled: the origin of the principle; the relativity of space and time; the relativity of the electromagnetic vectors; mechanics and the principle of relativity; Minkowski’s four-dimension vectors. I n the second part the headings of the chapters are: the general theory; verification of Einstein’s theory; further generalization, Weyl’s theory of electricity. When discussing the Fitzgerald contraction, the author says, p. 65: “ I t is clear that there are two gaps in this argument. First, there is the obvious restriction that it must be assumed that, provided that the acceleration of the body is sufficiently slow, so as not to produce mechanical distortion, change of temperature or other disturbances, there is a unique configuration for a given grouping of electrons moving as a whole with a given velocity relative to the aether. This does not seem to offer any serious difficulty, though i t must be remembered that the external configuration of a material body must be thought of as a statistical one; that is, in view of a probable kinetic constitution, to a fixed external configuration will correspond a multitude of rapidly changing distributions of electrons in the interior; but this will not be considered here. The more important point for discussion is that the correlation which has been shown to exist in the case of the ‘field equations,’ must be assumed t o hold for all the other relations which play a part in determining the motions of the electrons. “It has been remarked that i t is enough for the purpose in hand t o supplement the field equations by a hypothetical relation between the distribution of the charge that constitutes the electron and its velocity. If this is done, it must be a relation which maintains its form in the correlated moving system that we have built up. Since it is a purely geometrical relation it must be a relation which is invariant under, or is a consequence of, the fundamental transformation (A). Hence Lorentz’s assumption that the electron, which is naturally thought of as symmetrical round a centre when it is a t rest, is, when in motion, of spheroidal shape, being obtained from the spherical stationary electron by the simple application to it of the FitzGerald contraction. If this is not assumed, the correlation between the stationary and the moving system is not perfect, and we have

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reason, therefore, for thinking that the desired contraction of the whole body will take place. “Thus the whole explanation reduces to the formation of a conception of the electron, which really embodies the fact that we are trying to explain. The origin of the contraction is left in obscurity. The conception is only arrived a t by assuming the result of the experiment to be, not an accident arising out of the particular circumstances of the case, but inherent in the constitution of matter down to its most minute elements. In other words, the formation of this conception of the electron i s itself a direct application of the Principle of Relativity.” On p. 125 the author points out one weakness in Einstein’s presentation. “In the preceding chapter the order of the argument has been mainly historical; the purpose has been to give a straight-forward account of Einstein’s method and results. Before concluding, it is worth while however to recapitulate and to see the general lines upon which a radical reconstruction of physical theory must proceed. We shall see that even Einstein’s generalized relativity is not the last word, and an attempt will be made to indicate the lines along which Weyl had shown that it is possible by a further step to give to electricity as natural a place as that accorded to gravitation in Einstein’s theory. Einstein himself has shown that it is possible to generalize the fundamental equations of electrical theory so that they have an invariant form, and are therefore consistent with the Principle of Relativity in the sense in which he uses the term. But in his treatment the connection between the gravitational field and the geometry of the measure system is so intimate, while that between the electrical field and the measure system is so remote, that the fundamental place accorded to electricity in modern thought seems to be denied. In Weyl’s theory it is completely restored, and gravitation and electricity rank together as two fundamental properties of matter, forming together the basis of all natural systems of measurement.” On page 144 the author gives a comparative survey of the situation a t present. “It may be worth while to set down here a comparison of the conclusions from Newton’s theory of dynamics, Einstein’s restricted Principle of Relativity, Einstein’s generalized theory, and finally Weyl’s theory. I. IC’EWTON.-h the region of dynamics, of all possible co-ordinate systems there is a limited group for which the laws of motion have a particularly simple form. In any system of the group the path of a free particle is a straight line described uniformly. T I . EINSTEIN,1905.-Restricted Principle of Relativity.-In the region of dynamics and electro-dynamics, of all possible co-ordinate systems there is a limited group for which the laws are of precisely the same form. In any system of this group the path of a free particle is a straight line described uniformly, and light travels with constant velocity. 111. EINSTIEN,1915.--General Principle of Relativity.-In the region of gravitational phenomena, there is no restriction on the co-ordinate system but the measure-system is limited by the hypothesis (i) that the world-line of free particle is a direct line of the measure-system, (ii) that the curvature G may be identified with the presence of matter. The interval between two events is a fixed quantity within the appropriate measure-system.

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IV WEYL’S THEORY.-h electro-dynamic as in gravitational phenomena, there is no restriction on the co-ordinate system, and the measures of the interval between two events is not a definite quantity determined by the gravitation field. But of all possible measure-systems, there is one, or a limited group, in which the singular regions of the system are in exact correspondence with the regions in which matter or electricity are present. “We conclude then that Einstein has satisfied the demand that nature itself shall not show any preierence for any particular system of variables or coordinates by which we shall distinguish between events. Further, Weyl has made it clear that the laws of nature do not supply us with an absolute criterion of equality of intervals of space and time, except that of coincidence; in fact the idea of a definite measurable interval between two events has to some extent broken down. But we are not left with the conclusion that we may adopt an absolutely arbitrary system of measurement. There is necessarily one measuresystem for a limited group, within which there i s complete relativity, of co-ordinates, in which there is a particularly simple correspondence between the geometry of the system and nature; or in other words, for which the mathematical relations of nature take the simplest possible form. “In the end we must admit therefore that the recognition of order in the sequences of events around us arises from an adjustment of mental machinery to the events. Just as we only recognize a star as a sharp point of light when the eye focusses the light on the retina, so we recognize a distinct order in the universe when we focus our measuring system properly. The eye has an infinity of ways of focussing itself so that the star produces a blurred image on the retina. So the mind may form many images of nature which are in a sense blurred, in which a distinct order is not perceptible. But the fact that the eye can produce a sharp image is enough both to determine our conception of the star, and to define what we mean by the proper focus for the star. So the problem of science is mainly to discover that mental focus in which nature gives us clear impressions of order. Einstein has shown that this may be done in a way far more comprehensive than had been thought possible. He has shown us that the required mental focus is to be attained without any introduction of metaphysical notions such as those of an asolbute space and time, or even of such a remnant of those notions as that light shall have a definite velocity the same at all points.” Wilder D. Bancroft Anthracene and Anthraquinone. B y E . de Barry Barnett. 21 X 14 cna; pp. xi 436. New York: D . V a n Nostrand Company, 1921. Price: $6.00.It is over forty years since Auerbach published his book on “Anthracene and its Derivatives” and there have been many developments since then. Most important of them is that many of the valuable fast dyes belong in this category. The author has therefore given a fairly complete account of the work which has been published up to November 1920, on the derivatives of anthracene and anthraquinone, but not including such derivatives as chrysarobin, etc., which occur in nature and which are taken up in the book by Perkin and Everest entitled “Natural Organic Coloring Matters.” The subject is presented under the general headings: introduction; anthracene and its homologues; simple derivatives of anthracene; the anthraquinones

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and dianthraquinonyl;; anthrone, anthranol and allied products ; anthraquinone and ring syntheses; the benzanthraquinones; the aldehydes, ketones and carboxylic acids; the nitro, nitroso, and halogen anthraquinones; the sulphonic acids, mercaptans and sulphides; the aminoanthraquinones and dianthraquinonylamines ; the hydroxy and aminohydroxy anthraquinones and ethers; pyridine and quinoline derivatives; the acridones, kanthones, and thioxanthones; the benzanthrones; the cyclic azines and hydroazines ; miscellaneous heterocyclic compounds ; miscellaneous compounds. The book is written primarily for the organic chemist; but there are many things in it which will appeal to the physical chemist. On p. 5 there are a few notes on dyeing. On p. 40 we note that reduction of anthracene with nickel and hydrogen does not necessarily give the same products as reduction with sodium amalgam. The changes of nitroxanthone, p. 60, should be studied. The colloid chemist will be interested in the technical method of powdering anthracene, p. 74, and the electrochemist in the use of ceric sulphate as a catalytic agent in oxidation, p. 75. Everybody will want to know why magnesium chloride increases the oxidation by sodium nitrate or chlorate, p. 75. Equilibrium relations should be determined for the compound obtained by reducing diphenylOn p. 184 there are some remarks anthrone and treating with bromine, p:104. on dyeing with mercaptans. The effect of boric acid is interesting, p. 243. “It appears that the nitro group is particularly easily replaced when it is in the para- position to a hydroxyl group, and under these circumstances the reaction is best carried out by heating with concentrated sulphuric acid in the presence of boric acid. The action of the boric acid in this case seems to be specific and not to be limited to protecting hydroxyl groups, as dinitroanthrarufin is stable towards concentrated sulphuric acid a t 100’ in the absence of boric acid, but in the presence of boric acid one nitro group is replaced by a hydroxyl group a t this temperature, and a t higher temperatures both are replaced. Dinitroanthrarufin disulphonic acid exhibits the same behaviour, as it is unaffected when heated for four hours a t 150” with concentrated sulphuric acid in the absence of boric acid, but in the presence of boric acid one nitro group is easily replaced a t 80 “-90 O , and both are replaced a t 1 2 0 O . ” Boric acid is important in another capacity, p. 256. “When sulphuric acid acts as an oxidising agent it is, of course, reduced to sulphurous acid and this combines with the hydroxy compound produced to form a sulphite ester, this ester formation to some extent protecting the hydroxylated anthraquinone from destruction by further oxidation. Much more satisfactory results are obtained, however, by carrying out the oxidation in the presence of boric acid so that the boric ester is formed, and the same method is used when the oxidation is carried out with sulphuric acid and an oxidising agent. I n any case when oxidation is complete the melt must be diluted and then boiled in order to hydrolyse the ester present. When the boric acid method is employed it is usual to add one part of crystallised boric acid to twenty parts of concentrated sulphuric acid, monohydrate, or oleum, and then to add the anthraquinone compound (one part) which it is desired t o oxidise. The temperature is then maintained a t a suitable point until examination of a sample shows that oxidation has gone as far as

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desired, when the whole is cooled, diluted with water, boiled t o hydrolyse the ester, and the hydroxy compound then filtered off. “The addition of boric acid also slows down the reaction and, if sufficient is added, may even in some cases inhibit i t altogether. This retarding action of boric acid is often very useful in preventing the reaction going too far. Thus the oxidation of alizarin with oleum of high concentration leads t o quinalizarin in the absence of boric acid, but with the addition of a suitable amount of boric acid the reaction is so retarded that an almost quantitative yield of hydroxyanthrarufin can be obtained. I n the same way the addition of boric acid , . renders it possible to oxidise chrysazin t o 1.4.8-trihydroxyanthraquinone.. “Oxidation by means of sulphuric acid is a catalytic reaction and does not take place if chemically pure acids are used. When ordinary commercial acids are employed the small quantities of selenium present act as the catalyst:

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SeO2 = Se 0 Se 2S03 = SeOz

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2

+ 2S02

Oxidation by means of sulphuric acid is also facilitated by the presence of mercury compounds, and bromide is stated to facilitate attack by oleum, although this can hardly be regarded as a catalytic effect as bromination and hydroxylation take place simultaneously. Hydroxylation by oxidation with sulphuric acid or oleum often leads t o the production of polyhydroxyanthraquinone sulphonic acids, but in many cases the sulphonic acid groups are readily removed by hydrolysis by heating the product with sulphuric acid of about 70 percent strength.” When alizarin is sulphonated in the presence of mercury, the products obtained are not the same as those which are formed in the absence of mercury, p. 278. “When Alizarin Blue and similarly constituted dyestuffs are allowed to remain in contact with concentrated aqueous solutions of sodium bisulphite for several days they combine with two molecules of the bisulphite and pass into water-soluble products which are very largely used in printing (Alizarin Blue S,Alizarin Green S, etc.). I n text-books on tinctorial chemistry these soluble products are usually represented as being formed by union of the bisulphite with the cyclic carbonyl groups, but such a structure is very improbable as neither anthraquinone itself nor the hydroxyanthraquinones Sombine with bisulphite. Quinoline itself, however, forms an addition product with sodium bisulphite, and this resembles Alizarin Blue S by being decomposed by water a t 60”. It is therefore probable that in the soluble dyes the bisulphite is united to the quinoline ring and not to the cyclic carbonyl groups.” Books of this sort are very important and this seems to be a good example Wilder D . Bancroft of the type. Die Welt der vernachliissigten Dimensionen. B y Wolfgang Ostwald. Fifth and sixth editions. 23 X 16 cm; p p . x i i 253. Dresden and Leipzig, 1921. Price: 7 shillings.-The fourth edition was reviewed last year (24, 592), The new edition-called the fifth and sixth-has about thirty-two pages more than the preceding one. Apparently the book sells extremely well in Germany; but one cannot help wondering how long it will be desirable t o patch up lectures Wilder D . Bancroft given in 1914 so that they will seem up to date.

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