NEW BOOKS Die Absorption. Gesammelte Abhandlungen uber Kolloide und Absorption. B y J . M . V a n Bemmelen. Mit Unterstiitzung des Verfassers neu herausgegeben von Wo. Ostwald. 16 X 2 4 cm; xl f 548 p p . Dresden: Theodor Steinkopfl, 1910. Price: paper, 12 marks; bound, 20 marks.-This volume contains the collected works of van Bemmelen on colloids and absorption. The titles of the fourteen papers are: the nature of colloids and their water contents; the ab-' sorbing power of the soil and the absorption compounds formed; the hydrogel of ferric oxide, crystalline hydrated ferric oxide, potassium ferrite and sodium ferrite; the hydrogel and the crystalline hydrate of cupric oxide; the absorption of water by colloids and especially by the silicic acid gel; the formation and structure of gels; absorption; the isotherms of colloidal ferric hydroxide a t 1 5 O ; the absorption of hydrochloric acid and potassium chloride from aqueous solutions b$ colloidal stannic oxide; absorption of substances from solutions; action of higher temperatures on the structure of the silicic acid hydrogel; absorption compounds of hydrogels when chemical compounds or solutions may also be formed; the difference between hydrates and hydrogels, and the modification of the hydrogels (zirconic and metazirconic acids) ; contribution to the knowledge of the properties of hydrogels during desiccation and rehydration. These papers are fundamental and it is a great assistance to the chemist to have them in a collected and easily accessible form. The advances made by van Bemmelen are really the result of two things: that he made quantitative measurements, and that he realized from the beginning that a gel is not a definite compound. Since the quantitative measurements were necessary in order to prove the second point, it would be possible to condense our statement more and to say that van Bemmelen realized and proved that a gel is not a definite compound. This does not sound like much to-day because the fact is so well known to most of us; but it was van Bemmelen who taught it to us and it was a tremendous step forward when he made it. Even in spite of his work, the beginner in chemistry is still taught that ferric hydroxide is a definite compound. The chemical world owes thanks to the editor and the publisher for the Wilder D . Bancroft appearance of this useful volume. Die Methoden zur Herstellung kolloider Ltisungen anorganischer Stoffe. Ein Hand- und Hilfsbuch fiir die Chemie ufid Industrie der Kolloide. By The Svedberg. I j X 23 cm; p p . xii + 512. Dresden: Theodor Steirtkopff, I 9 0 9 . Price: paper, 16 marks; bound, 18 marks.-The author distinguishes two methods of making colloidal solutions. In the condensation method so called, one starts from a true solution; in the dispersion method one starts from a precipitated material and causes it to go into solution. Under condensation methods we have four subdivisions: reduction; oxidation; hydrolysis; and miscellaneous. Under the dispersion methods we have only two sub-divisions : mechanical and chemical; electrical. Typical instances of the reduction method are the preparation of colloidal
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gold by means of hydrogen, methyl alcohol, or hydroxylamine; Carey Lea’s preparation of colloidal silver by means of ferrous sulphate, etc. ; Billitzer’s method of preparing colloidal gold, silver or mercury electrolytically. The most important instance of a n oxidation method is the preparation of colloidal sulphur from hydrogen sulphide. The best known case of hydrolysis is the preparation of colloidal ferric hydroxide. Under miscellaneous methods we have the preparation of colloidal arsenious sulphide in solutions where the concentration of ions is kept low, and the preparation of colloidal silver bromide in presence of gelatine as a protecting colloid. Typical instances of mechanical or chemical disintegration are found in the peptonizing action of caustic soda on a silicic acid gel or in the alternate action of alkaline and acid solutions on chromium, platinum, iridium, etc. Under the electrical dispersion methods we have the original process of Bredig and the modification of it by Svedberg. Under each sub-division the author has given a very satisfactory bibliography Wilder D . Bancroft and the book is a n excellent one from every point of view. The Relations between Chemical Constitution and Some Physical Properties. B y Samuel Smiles. 13 x 20 cm; p p . xiv $. 583. New I‘ork and London: Longmans, Greeib & Co., 1 9 1 0 . Price: $4.oo.-In the preface the author says: “As indicated by tbe title, this volume does not exhaustively treat of the whole subject in question. For various reasons a few physical properties have been omited from consideration, the more important being Crystalline Form, Optical Rotatory Power, Electric Conductivity, and Heat of Combustion. . . Some other physical properties, for example, Solubility, Dielectric Constant and Magnetic Susceptibility have been omitted because the relations between them and constitution are not yet sufficiently elucidated to call for special treatm e n t . . . . A book of this kind runs the risk of satisfying neither the physical chemist nor the structural chemist; but it is necessary to point out that it has been written from the stand-point of organic chemistry. This standpoint has been assumed both from necessity and from personal inclination, the former arising from the fact that by far the greater portion of research in this subject has been focused on the compounds of carbon.” The properties have been classified as mechanical, hermal, optical, and electrical. Under mechanical properties we find capillarity, viscosity, and volume relations. Under thermal properties we have specific heat, fusibility, and boiling point. The optical properties are sub-divided into: refractive and dispersive power; abrorption of light; fluorescence; and magnetic rotatory power. Anomalous electric absorpt on is the only electrical property discussed as such. The book seems to be worthy of the series. For personal reasons, the reviewer has been interested chiefly in the chapters on absorption of light, fluorescence, and anomalous electric absorption ; and he confesses to having read these much more carefully than the others. These are probably not the chapters to which most people will turn first. If the others get as much out of the book as the reviewer did, the au hor will have no cause to complain. Wilder D . Bancroft
*
New Books The Organic Chemistry of Nitrogen. B y Nevi1 Viment Sidgwick. 7I7 x 26 cm; be. x 415. Clarendon Press: Oxford, 1910. Price: 14 shillings *et.I n the preface, the author says: “ I t is becoming generally recognized that organic chemistry cannot be treated satisfactorily without reference to those questions of physical chemistry which it involves. To attempt a separation of the two is to refuse all the assistance which can be derived from what is really the quantitative side of chemistry. The various physical questions are, therefore, discussed as they arise. A full treatment of the phenomena of tautomerism would have required too great an interruption of the main current of thought; but I have tried to indicate the more important points in which they are illustrated by the bodies under consideration. The dynamics of organic reactions is a field which, in spite of the increasing amount recently devoted to it, is still very largely unexplored; and yet it is of the utmost value for elucidating the mechanism of chemical change. I have therefore, made the references to investigations of the velocity of reaction as complete as I could, and the methods of analysis adopted in each case have been described.” The subject is treated under four heads: compounds with no nitrogen directly attached to carbon; bodies containing one nitrogen atom attached to carbon; compounds containing an open chain of two or more nitrogen atoms; ring compounds. As the reviewer has said so often, this is the kind of a book which we want and the more we get of them the better. This particular one is a good specimen of the class and it is difficult to see how any chemist could glance through it without finding something of interest. On page 25, the author points out that even the determination of the concentration of hydroxyl ions does not necessarily give us the true strength of a base. In an ammoniacal solution, for instance, we have the non-hydrated base NH,, the undissociated hydrated base “,OH, and the dissociated hydrated base NH,. In the ordinary methods for determining basicity wemeasure the concentration of the ions in a solution in which the total concentration of the base in all three forms is known, the existence of the first form, the nonhydrated base NH, (or R,N) being neglected. The value of the strength calculated from this is not the true strength but what may be called the apparent strength. “Hence the apparent strength of the base is smaller than the real strength, and the more so the greater the proportion of anhydrous amine present. When, therefore, the strength of an organic base (other than quaternary) is spoken of, what is meant is the product of two factors, the hydration constant and the dissociation constant. And until recently there was no method known for determining either of these two factors separately. The measurement of the ionization is no use, as the hydration factor comes in to the same extent a t every dilution, The determination of the partition-coefficient between water and air or an organic solvent has been suggested; but this does not help us either. The concentration of the R,N in the other solvent is proportional to that of the R,N in water, and therefore, also to that of the R,NHOH: which leaves US where we were before. The problem has a t length been solved by Moore. He points out that all methods of solution must fail, in which the observations are all made a t the same temperature. If, however, we measure the partition-coefficients and the degree of dissociation a t different temperatures, and if we fur-
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ther make the assumption, which for small differences of temperature is justifiable, that the temperature coefficients of these two quantities are constant, we obtain a sufficient number of equations to solve the problems. In this way we can determine for any amine (for the method applies equally to all pseudoacids and pseudo-bases, and to such bodies as carbonic acid and the lactones) the proportion present in the non-hydrated form, and the true dissociationconstant. So far, the necessary data have only been obtained for three substances, piperidine (which does not concern us a t present), ammonia, and triethylamine. The results show that in an aqueous solution of ammonia a t 20°, about two-thirds is present as non-hydrated NH,, the rest being mainly “,OH and a small quantity of ions; in the case of triethylamine only about a third is in the anhydrous form, as (C,H,),N. From these data the true dissociation constants of these two bases can be calculated and are found to be a t zoo: Ammonia K = 5.23 X IO@ Triethylamine 64 X IO+. That is to say, the introduction of three ethyl groups into ammonia has increased the constants only twelve-fold. We should, therefore, expect that the introduction of a fourth ethyl group, in tetraethyl-ammonium hydroxide, would involve a further increase only to about 1 5 0 X IO-‘, which would mean that it was still a very weak base. But as a fact, the quaternary hydroxide is an excessively strong base, comparable to potash, for which K is too high to be measured and is certainly greater than one. I t therefore appears that the first three ethyl groups produce only a small increase in the basicity of ammonium hydrate, while that produced by the fourth is enormous. I t has long been known that the quaternary bases were far stronger than the others, but until the true dissociation constants had been determined it was possible that this might be due to the unknown quantity of anhydrous base present in the latter cases but not in the former. This is no longer possible; and the sudden increase in the quaternary bases certainly seems to point to a difference between their constitution and that of the hydroxides of the primary, secondary, and tertiary amines. If we are not prepared to accept a formula such as Werner’s, there are two possible explanations. One is that the data on which these calculations are based (especially those for triethylamine) may be incorrect. But even if they are to be accepted, and this sudden change of basicity really occurs, it can be explained on the assumption of analogous structures for the tertiary and quaternary hydroxides, and without having recourse to any new theories of valency. If we say that the five valencies of pentavalent nitrogen are all equal, this only means that the relation between any five groups and the nitrogen atom is determined by those groups themselves, so that (excluding stereoisomerism) isomeric arrangements are impossible. I t is nevertheless quite conceivable, and indeed probable, that three of the nitrogen valencies (those of trivalent nitrogen) are essentially different from the other two; and that when successive alkyl groups are introduced into ammonium hydrate they fill up these three places first. If so, the introduction of a fourth group, which must now take up one of the other two positions, may be expected to prodfice a n effect on the molecule different from that produced by any of the other three.” On p. 73 we find an interesting discussion of the diimines. “The absence of color in these compounds is important, in view of their
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undoubted quinoid structure. I t is commonly assumed that all quinoid compounds are colored, like the quinones themselves and there is even a tendency to suppose that nearly all colored aromatic derivatives contain a quinoid ring. But these views require to be reconsidered in view of the recent discoveries on the one hand of quinoid substances (like the imines) which are colorless, and on the other of colored bodies closely resembling the supposed quinoid) aromatic colored compounds, which cannot contain a quinoid ring because they are not aromatic derivatives a t all. “The causes which determine the absence of color among these quinone derivatives are not understood. I t seems certain that the simple quinoid compounds form two series, one colored, like the quinones themselves, and the other not. On the other hand, these bodies are capable of a further increase of color, which must be accompanied by some structural change. I n the triphenyl-methane series, for example, the feebly colored Homolka bases go over on treatment with acids into the brilliantly colored dyes. This is generally represented as the passage of trivalent into pentavalent nitrogen: (H,N.C,H,),C = C,H, = NH
+ (H,N.C,H,),C
=
C,H,
=
NH,CI.
But there is much evidence to show that the change of valency of the nitrogen is not sufficient to determine color: thus the diimine salts are colorless. I t is clear that the influence of a pentavalent nitrogen atom on the color depends largely on whether it has a hydrogen atom attached to it: if it has, then the effect on the color is much the same as if it was trivalent; if it has not, then its effect is usually quite different. The conversion of the group-NX, where X is a hydrocarbon radical, into -NX,HCI does not seem in general to influence the color, but its conversion into -NX,CI does so in a very marked way. Of this we have an example in the quinone imine derivatives which we have just been considering, and another (curiously in the opposite direction) in rosaniline dyes, where the change from -NEt, to -NEt,HCl is without effect, while the change to NEt,Cl destroys the influence of this group on the color altogether. This is one of the phenomena which suggest that there is a difference in constitution between bodies of the type R,NHX and those of the type R,NX. “We must therefore look for some other change of structure in the conversion of the Homolka bases into the rosaniline dyes. In this connection certain facts recently discovered by Willstatter with regard to the quinone-diimines are of great interest. If unsymmetrical dialkyl-6-phenylene-diamineis oxidized, brilliantly colored substances are produced, known from their discoverer as Wurster’s salts, which were supposed to be true diimine derivatives, e. g., HN = C,H, = N(CH,),CI. Further investigation has shown, however, that these bodies contain an atom t hydrogen more than this, they are bimolecular compounds (analo ous to the quinhydrones) of one molecule of the oxidation product with one molecule of the unoxidized diamine, and may be written: NH,CI
I1
.
. .
NH,
I
CH4
. . .
C6H4
N(CH,),CI
. . .
N(CH,),.
I1
I
the dotted lines indicating some unknown kind of linkage.
If they are further
New Books oxidized to the true diimines the color disappears. Willstatter suggests that this peculiar linkage, which he calls meriquinoid (partially quinoid), is the cause of color in bodies of this type. An analogous explanation would hold for the triphenylmethane dyes, the true dye having a linkage between the quinoid nucleus and one of the other nuclei, which would be absent in the Homolka base.” On p. 92 there is an interesting paragraph in regard to the imido chlorides. “ I n the case of the a-oxy-acids, such as glycollic acid, it was formerly supposed that the ture imido-acids could be isolated. Glycollic acid gives a normal amide CH,OH.CO.NH,; but if its anhydride is treated with ammonia, or its imido-ether is saponified, an isomeric substance is obtained, which was origin/OH , ally assumed to be the iso-amide or imidohydrine CH,QH.C
NNH’
“Analogous compounds have been obtained from other a-oxy-acids. The subject has been reinvestigated by Hantzsch and Voegeln, who have shown that the properties of these substances are incompatible with this structureand, indeed, as far as one can see, with any structure. They cannot be converted into the amides, a change which one would expect to occur with the utmost ease, and their molecular weight is twice that required by the simple formula. Their other properties are also most extraordinary. Though they are only weak bases, and are not acidic a t all, their solutions are very good conductors of electricity, so that their electrolytic behavior is that of salts. Moreover, though they are fairly stable to acids, they are easily decomposed by certain salts, such as calcium chloride, with the formation of a glycollate. No satisfactory hypothesis has yet been proposed to account for these phenomena.” I t is worth while noting that nitroso-butane, p. 1 2 2 , has a sublimation point below the melting point, 76’. Somebody should certainly work out more carefully the conditions determining the production of red and yellow salts, p. 174, from the nitrophenols. Under fulminic acid, p. 224, we find the following: “The overthrow of all two-carbon formulae and the final establishment of our knowledge of fulminic acid on a firm basis, is due to the work of Nef. He showed in the first place that all the evidence was in favor of its containing only one-carbon atom in the molecule. Its decomposition products are nearly all one-carbon bodies. I t is formed, as we have seen, by treating sodium nitromethane with mercuric chloride, and if treated with nitrous acid it is convert d f. into methyl-nitrolic acid H.C(NO,)NOH. If we take it as proved that there is only one carbon atom in the molecule and also consider the fact that on treatment with hydrochloric acid it gives hydroxylamine, only one formula is possible, namely H.0.N = C”. The real reason which prevented the earlier investigators from adopting such a one-carbon structure as this was their unwillingness to admit the existence of a dyad carbon atom. But this objection has been removed by Nef’s other work on dyad carbon, and he has been able to show that his formula is alone capable of explaining the very remarkable reactions of fulminic acid, while all subsequent work on these bodies has only served to confirm his views.” “The one thing needful to establish Nef’s formula beyond all doubt is a determination of the molecular weight. If it can be shown that fulminic acid con-
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tains only one carbon atom in the molecule, we have no alternative but to accept Nef’s view as to its structure. A direct determination of this magnitude is impossible, but indirect evidence of great force has recently been adduced, from the electrolytic behavior of the sodium salt in aqueous solution. The salt can be prepared by treating mercury fulminate in alcohol with sodium amalgam, and is fairly stable. On Nef’s theory it is the salt of a monobasic acid NaONC; on any other, the acid is dibasic, and the salt Na,(ONC),. Now van’t Hoff has shown that the alkaline salts of mono-basic acids in fifth to tenth normal solution give a value of the dissociation factor i of about 1.85,and those of dibasic acids about 2 . 5 . From this it follows that if sodium fulminate is NaONC, its apparent molecular weight in solution should be 35, but if it is Na,(ONC),, it should be about 52. From the depression of the freezing point in fifth-normal aqueous solution, it was found to be 34.9, agreeing with that required for the monomolecular formula. Again Ostwald found that the increase in molecular conductivity in passing from N/3a to N/1024 solution, for the salt of a monobasic acid was from 4 to 8 units, and for that of a dibasic acid about 11. The observed increase for sodium fulminate was 5 units. These results make it certain that the acid is monobasic, and has the formula HONC; and hence Nef’s view as to its structure must be adopted.” In the chapter on uric acid there is a delightful paragraph, p. 318, on the work of Medicus. “ I n 1875 Medicus published a most remarkable paper on the constitution of this group of compounds. He produced hardly any new facts; but sometimes on the basis of facts already known, and sometimes, apparently, on no basis a t all, he suggested formulae for nearly every known compound of the group-uric acid, xanthine, caffeine, theobromine, guanine, and hypoxanthine. The singular point is that with the exception of the position of one of the methyl groups in theobromine, all the formulae which Medicus proposed are absolutely correct; although it was not until the most recent work of Fischer, in which he revised and modified many of his own previous formulae, that they were recognized as being so.” On p. 378 we get a tentative explanation of the catalytic action of mercury on the oxidation of naphthalene by sulphur trioxide. “The catalytic influence of the mercury, which occurs in other cases of sulphonation as well, is remarkable, and a very probable explanation of it has been given by Dimroth. He has shown that if a mercury salt is heated with an aromatic derivative, a compound is formed in which one hydrogen on the ring is replaced by mercury. This subsitution is quite peculiar in that the position taken up by the mercury is not determined by the substituent already present: it is always ortho. Now it is found that if benzoic acid is sulphonated in the presence of mercury, the amount of meta and para acids produced is the same as if the mercury were not there; but in addition a considerable quantity of the o-sulphonic acid is formed, which is not obtained a t all in the absence of mercury. This shows that the catalytic influence of the mercury is due to the formation and decomposition of a mercury derivative, as it introduces the sulphonic group at the position which the mercury (but no substituent) would occupy.” Wilder D. Balzcroft
