NEW BOOKS Colloid Chemistry Theoretical and Applied. Edited by Jerome Alexander. Vol. I I I . $3 x l r cm;p p . 655. New York: Chemical Catalog Company, 1931. Price: $10.50. I n the preface the author eays: “There is a wealth of wisdom in ‘cooking recipes,’ despite the fact that this term is sometimes used as an acme of scientific mom. Time out of mind cooks have beaten the whites of eggs eeparately from the yolks, and secured light cake by carefully folding in the beaten leavening froth of the whites into the batter containing the yolks. The modem physical chemist fmda that the lipoid or fatty matter in the yolks makes the foam bubbles of the beaten whole egg so unstable that if you beat up the whole egg ‘your cake is all dough.’ Furthermore, the use of oils or fats as ‘foam killers’ has long been ‘ruleof-thumb’ practice in many industriea, and has also been frequently made w e of by seacaptains. I n fact, ‘to throw oil op the troubled waters’ has become proverbial. “The upshot of these remarks is that scientists must consider the existence of a longstanding practice as presumptive evidence that there is somethiag valuable in or about it and that exploration in that neighborhood, with impartial separation of gangue, should yield some nuggets of truth. Geologists frequently learn a great deal about the strata of certain regions by a careful examination of mineral grains in ant hills,” p. 3. “As to the arrangement of papers in Vols. I11 and IV, which conclude the series, the first group consists of subjects of interest to many industries, and comprises eleven papers on general principles and six papers dealing with mechanical or more specialized matters. The large second group (twenty-five papers) may, for want of a better. name, be termed t e l h i c ; for it deals with matters which are of the earth, earthy, beginning with geology and mineralogy, and running to metals, petroleum, asphalt and agriculture,” p. 5. The papers and authors are: Cohesion and Adhesion by J. W. McBain and Jerome Alexander; Some Practical Results of X-ray Researches on Colloids by G. L. Clark; Wetting of Solids by F. E. Bartell; Spontaneous Dispersion of Small Liquid Particles by N. Rashevsky; The Influence of Elaaticity and Permeability on the Swelling of Two-Phase Systems by Karl von Terzaghi; On the Rubber-like and Liquid-Crystalline States of Matter, in Connection with the Classification of Crystals and Molecules according to their Vectorial Fields by P. P. von Weimarn; Surface and Catalysis by E. F. Armstrong; Contact Catalysis by H. S. Taylor; Adaorption by Silica Gel, Theory and Applications by E. B. Miller; Colloid Factors in Water Supply by W. D. Turner and D. D. Jackson; Crushing and Fine Grinding of Quartz by Louis Navias; Colloid Mills and Comminution Chemistry by August Chwala; Suspensoids and their Electrical Precipitation by W. W. Strong; The SuperCentnfuge in Industry by E. M. James; Notes on Filtration with Special References to Metaiiltration by J. A. Pickard; the Flotation Process by G. H. Buchanan; Chemical Warfare by Jerome Alexander; Colloid Chemistry and Geology by R. E. Liesegang; Colloidal Minerals by Cornelius Doelter; Colloids in Glass by Alexander Silverman; Some Colloidal Properties of Sodium Silicate Solutions by William Stericker; Porcelain and Allied Ceramic Bodies by Louie Navias; Ceramic Refractories 88 Disperse Systems by E. W. Waahburn; The Colloidal Nature and Properties of Cements and Mortars by A. B. Searle; The Colloidal State in Metals and Alloys by Jerome Alexander; Colloidal Conditions in Metal Crystals by W. Guertler; Colloidal Systems in Metallography by Carl Benedicks; The Well-known Five Structures in Steel by KBtarB Honda; The R6le of Surface Energy on the Equilibria of Iron and Iron Carbide by Yap, Chu-phay; The Properties of Thin Films on Metals by U.R. Evans; The Colloids and the Corrosion of Iron by J. N. Friend; Colloid Chemistry and Petroleum by A. E. Dunstan; Colloid Chemistry of Petroleum by J. C. Morrell and Gustav Egloff; Colloid Chemistry and Petroleum by L. Gurwitsch; The Free Carbon of Coal Tar by J. M. Weka and C. R. Downs; Asphalt by E. J. Nellensteyn; Deflocculated Graphite by E. G. Acheson; Colloid Fuel by L. W. Bates; Soil Colloids by J. di Gleria and Fr. Zucker; The Colloidal Chemistry of the Soil by Richard Bradfield; Rapid Colloidal and
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Mechanical Analysis of Soils by G . J. Bouyoucos and M. M. McCool; The Colloid Chemistry of Wheat, Wheat Flour, and Wheat Flour Products by R. A. Gortner. “That thin films are very much stronger than an adhesive en masse is established by Crow’s results for soft solder and our much more striking instance of a wax-free shellac. Joints made with this shellac, which is fairly soft and quite pliable, actually withstood a pull of nearly 4000 lb. per sq. in. when a thin film was used between nickel surfaces. We have found that optically plane surfaces prepared at the National Physical Laboratory yield stronger joints than those which have not been prepared with such precision. An examination of the broken joint served to show how exceedingly thin was the film between those highly’pblished surfaces. The amount of adhesive attached to the metal was just sufficient to dim the lustre. Incidentally the results of the tests carried out with a shellaccreosote cement between optically plane surfaces of mild-steel and nickel prove beyond doubt that surface roughness plays but a negligible part in determining the strength of a ‘specific’ joint for here we have the smoothest pomible surfaces yielding stronger joints than those prepared in the ordinary way and which are therefore comparatively very rough, “p. 22. “Krishnamurti has found for samples of sugar, benzene, and naphthalene charcoals and carbon obtained by charring ash-f&e gelatin with molten sodium, together with colloidal graphite prepared by exploding graphite acid in a vacuum, that all showed the small angle scattering in a marked manner. The patterns showed two rings in addition to the central scattering, the first and prominent ring corresponding to the (002) reflection of graphite, having a spacing of about 3.8 A.U. as compared to 3.4 A.U. of graphite. The outer ring was fainter and broader and showed a spacing of 2 . 1 2A.U. comparable to the (I 1 1 ) spacing of graphite (2.06 A.U.). The observations accord with the idea that in the amorphous state the carbon atoms join together in clusters, forming highly anisotropic units, esaentially two dimensional; the thickness being about 1/3 the length or breadth. Assuming that the central scattering is due to the dimensions in the plane of the particle, and the first ring to its thickness, a rough calculation gives about 60 atoms of carbon per unit. This picture of the carbon particle agrees with chemical evidence, mainly its oxidation to mellitic acid and adsorptive properties,” p. 33. “Following the discovery of Krishnamurti that diffraction patterns of aqueous solutions of cane sugar, levulose and glucose were distinguished by intense scattering a t small angles due t o the dissolved molecules, it was then possible t o undertake the study of colloidal solutions for which the state of molecular aggregation has been the subject of much speculation. The molecular weight of dextrin calculated from the extent of “amorphous” scattering by means of the Bragg formula nk = zd sin 0 comes out 600, and for gelatin, 3,000, which are not improbable values. The solution of sodium oleate produced a ring due to the presence of big groups or micelles of sodium oleate in the solution. The extent of the gaseous scattering gave the dimension for the sodium oleate molecule, agreeing with that calculated from molecular weight and density. An excess of scattering directly adjoining the central spot, is due to big groups of ionic micelles described by McBain. Aqueous solutions of starch, tannic acid and gum arabic showed a further scattering a t small angles to the primary beam, due to the dissolved molecules or micelles. The molecular weights calculated from the extents of the coronas were 6,200, 3,134, and 2,810, respectively. Thus, a starch molecule contains about I O dextrin molecules united together, and a tannin micelle contains I O simple molecules of the formula CMHIOO~. The great importance of these studies is at once apparent, when it is considered that extremely valuable information should be obtained from biological fluids including blood, filtrable virus, etc. I n all these cases of amorphous solids, liquids and solutions, the X-ray patterns are characteristic in showing the presence of one or more diffraction bands, even though these may be ill defined. The purely amorphous Scattering where no maxima are present, evidently can exist only in the case of ideal gases. All of these newer investigations are in agreement with the contention by the writer that such a material as amorphous carbon represents an intermediate state designated as a paracrystalline, through which the atoms of carbon have to pass before obtaining the orderly arrangement underlying the graphite structure,” p. 34.
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“There has been a very considerable dieagreement concerning the structures of gutta percha and balata which are like rubber, polymers of isoprene. The discrepancies have a t last been explained in the work of Kopff and von Susich and of Stillwell and Clark. Thase two substances produce diffraction patterns different from rubber, but probably like each other. There are two modifications, the a which is stable below 60°C. and p produced by heating above 60”,giving different patterns in the unstretched state. The p-modification also produces a fiber pattern, since the specimens must be warmed before stretching. Stillwell and Clark have found balata in ordinary commercial form to ditrer from ordinary gutta percha, in the same way that von Susich’s p-modification differs from p-gutta percha,” P. 37. “A plausible mechanism for muscular action can be deduced in terms of inner molecular forces. Rubber contracts because of double bonds in the long hydrocarbon chains which cause a spring-like coiling. In muscle protein there are many free basic and acid groups in the chains, since glutaminic acid and arginine and lysine may be derived. At the isoelectric point COO - and NH’; ions may attract and pull the chain into a close spiral,” p. 39. “If wetting be defined as ‘that phenomenon which occurs when a solid phase and a liquid phase come in contact in any manner, so as to form a solid-liquid interface,’ the ground for controversy relative to wetting and non-wetting has been removed. There remains only the question of degree of wetting of the solid by the liquid. If it be further specified that degree of wetting means the amount of change in free surface energy which occurs (or the work done by the system) when the solid and liquid are brought together, all confusion can be avoided,” p. 41. “Carbon pigments are used as a fLller f o r rubber. Carbon gives an exceptionally high adhesion against the organic constituents of the rubber; this i s desirable as it results in a product of high elasticity and good wearing qualities. Over one hundred million pounds of carbon black are used per year in the rubber industry alone. Large quantities of carbon pigments are used also in printing inks, in stow polishes, and in shoe polishes. In each of these preparations the liquids used must give a high degree of wetting with the pigment. In printing inks the liquid medium must possess a fairly low surface tension in order to give a smooth flow over the surface with a minimum tendency for t’heink to pull up into drops; on the other hand ‘spreading wetting’ (the magnitude of which is increased as surface tension of liquid is decreased) against the paper cannot be too high, otherwise a sharp imprint will not be obtained,” p. 54. “Three different groups of facts lead, therefore, to the assumption that gelatine has a sponge or net-like structure,” p. 86. “A system possessing the high elasticity of rubber must have the following structure: (I) The primary structure elements of such a system must possess the form of spirally curled fibrils; (2) the interfibril dispersion medium must be extremely viscous (plastic) and permit the fibrils, after the stretching out of the system, to become curled when the system has been released from tension,” p. 96. “It is the specific nature of the catalyst which determines what the chemical change shall be. More closely studied from this point of view has been the reaction of carbon monoxide with one, two or three molecules of hydrogen, producing formaldehyde, methyl alcohol or methane respectively. Any desired one of these three products can be made with the practical exclusion of the others, provided that a suitable temperature and catalyst is selected. A copper catalyst a t 300’ to 400%. favors the formation of formaldehyde; to produce methyl alcohol a reduced basic zinc chromate is necessary a t 300” to 350°C., whilst for methane the beat catalyst is nickel at 150” to zoo”C. The reactions are carried out a t fairly high preeaures,” p. 103. “The linearity of the time-hydrogen-adsorption curve in casea of hydrogenation in liquid media is held to be evidence of interaction of the organic compound rather than the hydrogen with nickel, because the rate of absorption varies during the course of hydrogenation of many unsaturated substances containing two ethylenic linkages a t or near the point at which the material becomes semi-hydrogenated, and chemical analysis has shown in such c m that the reduction has been ‘selective,’ that is the two centres of uneaturation are reduced in number to one before any proportion of the singly unsaturated product is com-
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pletely hydrogenated. Consequently, the slope of the time-absorption line is definitely correlated with the organic compound present. It is d&able to emphasize this most striking feature whilst a t the same time bearing in mind that hydrogen undoubtedly also becomes sasociated with the nickel,” p. 105. “The extent of the surface which is active varies with the nature of the reaction catalyzed. There is unequivocal evidence that, in certain reactions, every atom in the surface is active. In others the evidence is equally definite that only a small fraction of the surface is active. In the former case the reaction is relatively insensitive to poisons, in the latter case extremely sensitive. Hence arises the possibility of progressive poisoning in which, on a given catalyst, different reactions are successively stopped by increasing amount of poison. The study by Vavon and Huson of a colloidal platinum on which the hydrogenation of propyl ketone, piperonal, and nitrobenzene were successively suppremed by addition of increasing quantities of sulfide poisons is a good example of such behavior,” p. 108. “When we turn from elementary catalysts such as the metals to catalystu composed of compound materials with ionic lattices such as oxides, halides, sulfates, eto., the surfaces in question contain an additional factor of variability. Such ionic lattices may be regarded as dual catalysts, the surface being composed of metal ion and negative ion. To each type of ion may be ascribed a definite and specific catalytic activity. Examination of the catalytic behavior of the oxides suggests that, on the metal ion, proceases of hydrogenation and dehydrogenation occur, whereas, on the oxide ion, the processes are essentially hydration and dehydration. With a given process, the extent of the two alternative changes will be determined by the relative extent of adsorption of reactant on the two ions, on the relative frequency of the two ions in the surface and on their specific individual catalytic activities. These several factors (extent of adsorption, frequency of ions in the surface and catalytic activity) will be determined by the degree of saturation of the lattice ions, and by the extent to which the ions are already covered by poisons (salts, water, ammonia, etc.). With this concept, the variation in dehydration-dehydrogenation ratio of various oxide catalysts in, for example, formic acid decomposition HCOOH = Hz COz CO HCOOH Hz0 and ethyl alcohol decomposition CsHsOH = CHzCHO Hz Hz0, CzHbOH GH, receives a more satisfactory interpretation than has hitherto been suggested for such reactions,” p. rog. “Probably the most important application of silica gel so far developed commercially is in the so-called contact sulfuric acid process. As a camer for platinum it is ideal. It is chemically inert to sulfuric acid a t high temperatures, stands up under continuous high temperature conditions, is resistant to mechanical action and offers an enormous surface upon which to distribute the platinum. Besides possessing these qualities silica gel mass has also proven insensitive to the usual negative effect of arsenic poisoning,” p. 133. “Micro-organisms often give trouble in reservoirs which at certain seasons may become literally hotbeds for the growth of various types of microscopic forms, which will contribute colloidal impurities to the water. The combined influences of warmth, sunlight, and quiet are all contributing factors which may sometimes be very difficult to alter. In certain regions reservoirs must be covered wherever possible to exclude sunlight, and thus inhibit microscopic growths. In Bermuda, for instance, where the climate is temperate, but the sun is hot, raw water cannot be stored in the sunlight for even forty-eight hours without becoming green from the prolific growth of chlorophyceae. All storage tanks in the region are, therefore, constructed with covers to keep out the light,” p. 137. “Red water occasionally gives trouble in certain water pipes, particularly, the system within private properties, and especially the hot water systems. This rusty discoloration is due to colloidal ferric iron in the water and is usually traceable to the effect of dieaolved air or oxygen on the walls of the iron pipe. The effect is noticed more frequently with soft water and obviously more so with hot water. In New York City the water is so soft that
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incrustation in water heaters takes place very slowly, or not at all. Here it is, therefore, not uncommon to find the water in hot water pipe lines running brick red from the i r o ~ contamination originating within the heater system,” p. 138. “Reaction of the negative colloidal color with the positive nucleus of the coagulating agent (copperas or alum) gives flocculation precipitation and decolorization, but as pointed out by Whipple colored waters having the negative property increased by addition of Con can be better decolorized by alum coagulation. This in conformity with the experience of Jackson, who found that the highly colored water in the Everglades region of Florida could be successfuUy decolorized, first, by adjustment of the hydrogen ion concentration by addition of so active an agent aa sulfur dioxide, followed by the cuatomary addition of alum coagulant,” p. 150. “The traces of certain impurities which may give trouble are sometimes astonkhingly small. This is well illustrated by an experience of the large rayon plant near Buffalo. Here it was definitely established that the discoloration in the top skeins of piles.of fiber through which they were running wash water was due to a trace of copper in the water which gave p. 153. trouble in concentrations as low aa one part in 40,000,000,” “Where no solvents are present, from solid non-gels there are formed only turbidities, provided that there are used aa peptizers only substances which are polar and relatively slightly active. Solvate$ on the other hand, form sole,but require aa peptizers very active molecules having the power to form true compounds which can faaten themselves to the particle surface. The slightly active polar substances which serve as peptizers for solid nongels, are incapable of orienting themselves on mlvates,” p. 188. “The sedimentation of BaciUus acidophilus from broth culture furnishes an interesting example of the ability of the centrifuge to remove finely divided solids. The bacilli, which vary in length from rp to 3p, and have a diameter of approximately 0.5p are formed in the broth culture under carefully controlled conditions. When the concentration of the bacilli has reached fifteen hundred million per cubic centimeter, the broth is ready for centrifugal treatment. It is fed through a battery of super-centrifuges a t the extremely low rate of I O gallons per hour, and the effluent, whose bacterial count haa been reduced to twenty-five million per cubic centimeter is wasted. When the centrifugal rotors are opened, the bacilli are found adhering to the wall of the bowl in a putty-lie m w . From this form they are worked up into a special preparation, providing extremely high bacterial concentration,” p. 2 1 0 . The tonnage of ore treated in the United States alone by the flotation prweas amounted “in 1929 to sixty million tons. At one metallurgical operation alone forty thousand tons of ore are treated daily,” p. 225. “The so-called ‘Sea of Darkneas’ in the Atlantic Ocean between Cape Verde Island and the Canaries, probably owes its origin to dust storms from the Sahara Desert, especially between January and April. According to Hellman and Meimardus, a cyclonic storm central over Tunis about March 8-10,1901,deposited about 150million tons of dust on the African coast, and further great but incalculable amounts in the Mediterranean Sea. So high did the dust rise, that about one-third of the 1,800,ootons deposited in Europe fell north of the Alps. E. R. Miller and A. W. Winchell traced a storm of dust-colored snow from Dubuque, Is., to Chelsea, Vt., over an area of IOO,OOO square miles; the dust, apparently originating in the deserts of Arizona and New Mexico, must have been carried at high altitudes for over 1,000miles before being brought down. The daily papers reported on December Igth, 1930, that a temfic storm swept over northern Algeria following a serious seven months drought; and on December 22nd the papers reported that a terrible fog (visibility 3 feet) had paralyzed London. Just prior to this (Nov. 27, 1930)a terrific sand-storm and hurricane blew over French Morocco, carrying a heavy deposit of yellow sand to the streets and foliage of Barcelona the next night. On the morning of Nov. 29th, a ‘Mud-rain’ fell in Paris, along the English Channel and the coast of Brittany. [See Jerome Alexander: Science, 63,96 (IgfI)],’’ p. 260. “The ascidian Phallusia has a vanadium-containing blood; manganese occurs in musaels; copper in most molluscs,” p. 275.
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“As a matter of fact, comparatively little is known about the chemical reactions of the sodium silicates in aqueous solutions. . . . If results are reported without specifying the silicate, many questions remain. As an example of the possible contradictions, the reaction with calcium carbonate studied by Carter, may be cited. He found that NstO.zSi02 would react with CaCOs; but that neither NalO.x.6SiOt nor Na20.3.3SiOz showed any evidence of reacting within a period of a week,” p. 29j. “Refractory materials are known to have extraordinarily high latent heats of fusion and consequently also very high heats of sublimation,” p. 352. It seems to the reviewer that the vapor pressure should increase rapidly with the temperature if the heat of sublimation is very high and that consequently refractories should sublime a t relatively low temperatures, in which case they would not be refractories. “It seems to the present writer [Alexander] that there is no good reason to doubt the existence of FesC, especially when the steel is semi-solid or solid, for there exists a condition of kinetic or dynamic equilibrium in which this compound is being continually formed and broken up, so that while a certain percent of free carbon atoms may exist a t any one moment, there is probably an enormously larger percentage of Fe3C. Viewed from the standpoint of a kinetic equilibrium, all difficulty regarding the diffusion of Fed2 dieappear,” p. 429. “Cold bauxite, which has been ignited and cooled in a vacuum desiccator was found to have lost its power of adsorbing sulfur derivatives from kerosene. When freshly heated (to 200°C.) its activity in this direction was regained. Heat appears to be evolved during active adsorption, thus a 20°C. rise in temperature was observed during the passage of 100 cc. of kerosene through j o grams of bauxite,” p. 494. “It is estimated that in 1930 three hundred million barrels of the world’s total crude oil production was produced in emulsion form, and required some form of treatment before it could be marketed,” p. 504. “From the economic point of view colloidal fuel possesses many advantages over fuel oil or coal alone. First, the fire hazard of colloidal fuel is less than that of oil or coal. The specific gravity of a composite using over about 15 percent of coal is greater than unity. If on fire, the flames may be quenched in and by water, and, in storage, fire may be prevented by a water seal. This fact is of cardinal importance as other liquid fuels are lighter than water and cannot be so safeguarded. Trials of a water seal have shown that certain grades of the fuel may be so stored for even a year without jeopardizing their operative character. Sprinkler systems of fire protection do not lose their utility as they do in plants using oil fuel. The insurance advantage and increased safety of ships and plants due to this fireproofing capacity is obvious,” p. 557. “The great interest practical soil chemists have shown in base exchange phenomena in the last few years is due largely to the fact that an understanding of these reactions promises to throw much light on several of the most important problems in soil management. Such studies as indicated above have served to greatly clarify some of the problems connected with the acid soils of the humid region. The proportion of exchangeable hydrogen in the colloidal fraction, or the “degree of unsaturation with bases” as it is commonly called, is one of the best measures we have of the degree of acidity of a soil,” p. 587. Wilder D. Bancrojt Essentials of Quantitative Chemical Analysis. By Wilfred W . Scott. 63 X 15 cm;p p . 919. Easton: The Chemical Publishing Co., 1931. Price: $6.75. This is a new and enlarged edition of Scott’s “Inorganic Quantitative Chemical Analysis,” 1926. The text contains a comprehensive list of experiments of general educational value for students in introductory quantitative analysis. The arrangement is much the same as the previous addition although several procedures have been entirely rewritten and a number of new methods have been introduced. The notes and theoretical discussions accompanying the experiments have been increased over those of the previous edition. Numerous references for outside reading and a list of study questions in the addenda of the text are also included. M . L. Nachols. vizi
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Handbuch der allgemeinen Chemie. Edited by Paul Walden and Carl Drucker. Vol. VIII. Part I . Elektromoton‘sche Krafte. &I R. Kremann and Robert M i i l k . 95 X 17
cm: p p . zvi + 851. Leipzig: Akademische Verlagsgesellschafl,1530. Price: 81 marks; bound, 85 marks. This volume covers the whole field of electromotive forces, not dfierentiating between aqueous and non-aqueous solutions. The chapters are entitled: introduction; measurements of elect,romotive forces; conversion of chemical energy into electrical energy by means of galvanic [voltaic] cells and the temperature coefficient of such cells; Nernst’s osmotic theory of the galvanic production of current; solution cells; concentration cells; amalgam cells; galvanic cells of the Daniell type; effect of pressure on reversible galvanic cells-gravity cells; determination of single potential differences a t phase boundaries in galvanic cells; potential dfierencea a t other phase boundaries than those between metals and solutions; electrolytic solution pressure; single potential in cells; potentials of alloys; oxidation-reduction cells; normal potentials of electrode reactions; formation of metals and alloys by precipitstion. “The current in ace11 of the Daniell type is due t o the fact that the less noble metal (zinc) dissolves, sending positive ions into the solution, and becoming charged negatively itself, while simultaneously equivalent amounts of the ions of the nobler metal (copper) are precipitated on the copper electrode, thereby charging this positively. The equalization of the potential differences takes place in the external circuit with production of electrical work,” p. 4. On p. 13 the authors say that Helmholtz later developed independently the Gibbs formula, This is not true at, all. Gibbs developed a theory to show that the electrical energy of a reversible cell is not necessarily equal to the heat of reaction. When Helmholtz deduced the equation for the relation between electromotive force, temperature coefficient, and heat effect, Gibbs showed that the same equation could he deduced from the Gibbs theory. Gibbs did not deduce it, and there is nothing to show that he would have deduced it if Helmholtz had not done so. On p. 20 and elsewhere throughout the book the authors write the formula of mercurour chloride as HgC1, although they cite Ogg’s work, p. 99, showing that the mercury ion is Hg,. Eight pages are given, p. 38, to the application of Nernst’s heat theorem to voltaic cells. A good compilation is given, p. I I I , of the data on concentration cells in non-aqueous solvents. On p. 132 there is a warning as to errors in electrometric titration caused by adsorption. The authors do not seem to know, p. 136,that there is a1waye.retrograde solubility with rising temperature whenever a binary compound is stable at its melting-point. I t is difficult to tell, p. 144,what the authors’ attitude is towards Spencer’s peasurements on amalgam cells. On p. 213is given the deduction by Gans of the effect of pressure on electro. motive force when the transference number varies. “Arrhenius showed that air can act as an electrolyte. If one brings a zinc wire and a platinum wire into a tube pumped out to a pressure of 0.1-2.0cm, and if one makes the air a conductor by means of cathode rays, a current is obtained between the metals flowing in the direction that it would if the metals were dipped in air; the electromotive force averaged about 0.86volt,” p. 221. It is recognized, p. 248, that the maximum-surface-tension method does not give the true single-potential difference because of adsorption; hut nobody seems to have determined the absolute maximum-surface-tension of mercury in any of these solutions. If the value in sulphate solutions were very close to the true surface tension, the error would be very small. If it were very large, the error would be correspondingly large and there might even be an agreement between this method and that of Billiter. The theory of Frunkin, p. 256, does not appear to come out with anything positive. The authors throw out Billiter’s work, p. 276,because the potential difference of silver against a solution is a function of other things besides silver ions; hut the potential difference of a hydrogen electrode is a function of chloride, bromide, and iodide ions. There is a very good account of Haber’s work on phase boundary potentials, p. 281;of membrane cells, p. 291;and of the Donnan equilibrium, p. 299. On the other hand, they quote with approval, p. 325, Luther’s statement that the potential difference hetween a
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metal and a saturated solution of a ealt of the metal is independent of the nature of the solvent. The discussion of the change of the solution pressure with the solvent, p. 326, is rather exceptionally poor. From a, table for heats of ionization of metals, p. 351, the authors draw the conclusion that all metals which form ionsreadily have positive heats of ionization, while others have negative heats of ionization. Tin seems to be an exception. I n the disouesion of the hydrogen-lead peroxide cell, p. 362, the authors point out that a much larger current can be drawn without polarization with palladium electrodes than with platinum electrodes. Apparently the rate of conversion of molecular into atomic hydrogen is much lower with platinum than with palladium. Also the oxygen polarization of the platinum electrode poisons the latter. Addition of colloidal platinum to a solution, p. 439, makes it possible to use smooth platinum electrodes. Strong poisons for metals, p. 441,are naphthoquinoline, strychnine, brucine, narcotine, and quinine. Less strong are nicotine, veratrine, cocaine, and cinchonine. Amalgamated aluminum in N / I OAlCl, gives a potential difference of 1.66 volts against the normal calomel electrode. Since aluminum cannot be precipitated from an aqueous solution, the aluminum electrode is theoretically irreversible and its electromotive force is consequently not a function of the concentration of aluminum ions. This is not true for a fused mixture of aluminum and potaesium bromides, p. 476. Aluminum dissolved much more rapidly in hydrochloric acid than in equimolecular hydrobromic or hydriodic acid, p. 477. The authors draw the apparently unwarranted conclusion that the rate of attack is proportional to the concentration of the undiasociated acid. Since iron takes up hydrogen readily and also oxidizes readily in water, its potential is hard to determine. The authors consider eh = -0.46 88 representing the equilibrium potential, p. 541. The intermittent action of acids on chromium is believed to be due to iron in the metal, p. 557. With pure iron in chromic acid, periodic fluctuations of 0.4 volts can be obtained, 558. While sulphur may form quadrivalent cations, aa indicated by the conductivity of liquid sulphur dioxide, it is not legitimate to postulate this from the fact that sulphur ie set free at the cathode in the electrolysis of concentrated sulphuric acid, p. 573. That sulphur comes from the interaction of sulphurous acid with hydrogen sulphide. If one superposes an alternating current on a direct current one can get evolution of hydrogen and oxygen below the point of reversible equilibrium for the oxyhydrogen gas cell. On increaaing the alternating current relatively to the direct current, Grube and Dulk found a break in N NaOH at 1.24-1.26 volts which is very close to the theoretical value of 1.237 volts, p. 589. The experiments of Tartar and Wellmann show that soluble substances. possibly hydrogen peroxide, are also a factor, p. 590. If platinum is precipitated electrolytically on porous charcoal, a film is obtained through which hydrogen paaaes with great eaae and permits 8 current of twenty milliamperes per square centimeter, p. 613. Butler, Hugh and Hey find that constant potentials as nonattackable electrodes are reached by platinum, palladium, iridium, osmium, gold, rhodium, and ruthenium in about an hour, while molybdenum, tungsten, nickel, silver, and mercury are not certain to give constant potentials a t all, p. 663. The treatment of the effect of hydrogen ions on the potential difference due to oxidizing and reducing agents is perfunctory and unsatisfactory, p. 669. There are a number of interesting facts on p. 697. A ferrous-ferric salt solution can be prepared which will precipitate silver and not copper. Addition of sodium fluoride causes the precipitation of metallic copper. An alkaline stannite solution precipitates metallic cadmium. There is a distinct over-voltage for hydrogen in vanadous chloride solutions, which can be overcome by platinum metal. Sixteen pages are given to the quinhydrone electrode, p. 713. It is not clear why cane sugar should affect the readings but it does. p. 723. On pp. 786790 there is a fairly complete table of electromotive force measurements depending on oxidation or reduction. The book is a marvellously good one as a collection of facts. The authors are worshippers of the letter, however, and no one will turn to them for inspiration. Wilder D. B a w o f t
