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Colloid Chemistry. Edited by Jerome Alexander. Vol. I. 23 X 16 cna; p p . 974. Neu York: Chemical Catalog Company, 1926. Price: $14.60 This is a miscellaneous collection of papers by miscellaneous authors. “R’ot only has no effort been made to select contributors whose ideas and opinions agree on all points; but, on the contrary, the proponents and exponents of diverse and even conflicting views have been asked to state their ideas freely and without reserve.” This means interesting pspers but considerable overlapping and relatively little co-ordination. The papers and authors in this volume are: the submicroscopic structure of matter, Jerome Alexander; theory of the colloid state of matter, P. P. von Weimarn; the mesomorphic states of matter, G. Friedel; colloids as one-phase system, E. Buchner; the states of matter exemplified by a typical colloid-soap and the soap-boiling process, J. K.RlcBain; determination of size and mass of colloidal particles, E. F. Burton; measuring the electron and checking the kinetic theory by ultra-miscroscopic observations on minute droplets, R. A . hlillikan; surface energy and surface tension, W.D. Harkins; cohesion and molecular forces, Sir William H. Bragg; surface tension of colloidal solutions and dimensions of certain organic molecules, P. Lecomte du Kouy; surface films as plastic solids, R. E. Wilson; molecular association, W. E. S. Turner; friction, surface energy, and lubrication, Sir Killiam B. Hardy; the mechanism of coagulation, H. R. Kruyt; theory of the opalescence of homologous liquids and mixtures of liquids in the vicinity of the critical state, Albert Einstein; the scattering of light in one-phase systems, 11’. H. Martin; the effect of emulsoids on colored solutions, Hsien K u and Daisy Pen Wu; aerosols, IT. E. Gibbs; atmospheric nucleation, Carl Barus; colloid meteorology, W. J. Humphreys; colloidal water and ice, H. T. Barnes; astronomy, H. S. Russell; the planetesimal hypothesis, W.D. Maellillan; the thermal chemistry of colloids, F. L. Broivne and J. H. AIatheivs; electric phenomena in colloid chemistry, Leonor Michaelis; the specific inductive capacity of substances in the colloidal state, Jacqum Errera; the osmotic pressure of colloidal solutions, J. Duclaux; the effects of molecular dissymetry on some propert,ies of matter, Irving Langmuir; physics, chemistry, and the colloidal state, K.Kopacewski; adsorption and its significance, Herbert Freundlich; adsorption by precipitates, H. B. Weiser; some novel aspects of colloidal protwtion, Jerome :Uexander; fibrous alumina, H. Wislicenus; the influence of colloids on the solubilit,y of colloids, H. J. Creighton; solubility and size of particles, G. A . Hulett, attraction intrnsity and attraction pressure, J. Tra.ube; quantitative investigations on the changes in strength of union with water exhibited by hydrat,es with crystallization water when their degree of dispersity is vhanged by mechanical means, Tokutaro Hagiwara; quantitative researches on dispersoid synthesis, Senji 1-tzino; difficultly soluble silver salts, their preparation and properties, A. Lottermoser; constitution of the dispersed micelle in platinum electrosols, A. de G. Iiocosolano; pyrosols, Richard Lorenz; the adsorption of gases by metah, L. L. Bircumshaw; fluidity and plasticity, E. C. Bingham; consistency, W. H. Herschel; the viscosity of colloidal solutions, Emil Hatschek; the sol-gel transformation and the properties of jellies, s. C. Bradford; t,he problem of gel structure, D. J. Lloyd; diffusion in jellies, E. E Liesegang; banded precipitates in porous media, S. C. Bradford; reactions in gels, H. S . Holmes; the crystallization of sulphur in rubber, H. A. Endres; ultramicroscopy, Max Poser: the immersion ultramicroscope, Richard Zsigmondy; ultrafiltration and electroultrafiltration, H. Bechhold; cent’rifugal and diffusion methods for the study of dispersity and hydration in sols, The Svedberg; subsidence in colloidal systems, E. I?. .iyres, Jr.; sedimentation-analysis and its application to the physical chemistry of clays and precipitates, Sven O d h ; the colloidal aspect of analytical chemistry, Henry Bassett ; membrane filters and their uses, Richard Zsigmondy. I t is claimed by von Weimarn, p. 85, that crystals go through a colloidal stage of solution when they dissolve; but all he really shows is that a crystal may become very small just
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According to R. E. Wilson, p. 277, “solutions which form plastic solid films give erroneously high values for their surface tensions by the du Nouy and presumably by other methods of measurement, because the yield value of the plastic solid film is added to the true reversible surface tension.” Hardy states, p. 299, that “water has a profoundly disturbing effect upon the lubricating properties of other substances. Its vapor will, for instance, almost wholly destroy the lubricating properties of an alcohol. On the other hand, water can be an excellent lubricant It is such for ebonite, or for glass or steel when already covered with a film of a solid luhricant which does not dissolve in water. These apparently contrary properties were found to be reconcilable when the influence of water iT-as followed in a number of cases K h e n water vapor is admitted to the chamber its influence on the friction of clean surfaceq of glass, quartz, or steel is nil; but if the surfaces have already been lubricated by a primary film, water vapor lowers frictzon ff the lubricant i s zmnaisczble with water and raises friction zf the contrarq as true. KO exception to this simple rule was found. “Up to a certain point the mode of action of the vapor is clear. Consider, as the simplest case, a surface coated with a primary film of a solid paraffin. Water vapor diminishes the friction of the surface of a block of solid paraffin,-the vapor condenses as an insensible primary film of water xhich has considerable lubricating power. . . . When, therefore, surfactas of glass or steel are coated with a layer of paraffin, mater d l reduce their friction even though the layer of paraffin be only a film of insensible thickness. ‘ V e must, therefore, suppose that when water vapor condenses on to a primary film of paraffin on :I solid, the value of p is that given by four primary films, two mrdinn ones of water, two outer ones of paraffin, one on each solid face, and the conclusion reached is that four films lubricate better than two. This may be of the nature of a general law ” Price has suggested that “the destruction of Sodom and Gomorrah by a rain of h i m stone and fire can be attributed to a charged mist of petroleum formed in the Caucasus by the outburst of an oil spring, and carried southward to the cities of the plain. There it reached the isoelectric point, flocculated, and was precipitated as rain and became ignited by lightning. Similar self-ignited oil-clouds are a familiar phenomenon in the Caucasuq,” P. 419 “Probably the most interesting form of fog is the intense black fog which sometimes occurs during the very cold weather over the open surface of the St. Lawrence. Mists aiid winter fog are quite common over this river whenever the temperature goes beloxv 11°F. The black fog occurs only at sub-zero temperatures and appears to be a heavy precipitation of semi-fluid globular particles which in their formation absorb completely the energy of the sunlight. I t is preceded by a white fog, which, early in the morning may rise t o heights of 1200 feet in long streamers. With the rising of the sun the white fog subrides aiid the color changes to a sulphur yellow like burning saw-dust, and then rapidly to deep opaque black at the bottom. This shuts out completely all view of the water, of objects on the surface, and of the opposite shore. In Fig. 2 I show a photograph taken last winter of one of the thickest black fogs ever known on the river. Fig. 2 was taken at 9 a. m. just after the sun had driven the fog down, and shows the black blanket over the entire water surface between the edges of the border ice fields. “On rowing out into this fog the temperature was much higher than the surrounding air and the blanket felt quite n-arm to the face, proving what an effective protection this fog is to the loss of heat from the water. The white fog can be readily seen to consist of plates and minute particles which are deposited along the shore on the grass and trees and give rise to some very beautiful sights,” (Barnes, p. 439). Bradford states, p. 7 6 2 , that “small additions of alcohol to warm one percent gelatine solutions, which are not saturated above about 26‘ or 27O, increase the large amounts of salt solutions required to salt out the gelatine. But, when more than a certain quantity of alcohol has been added, the solutions become opalescent and very small amounts of salts are sufficient to cause precipitation. The explanation is, probably, that the solubilitr of gelatine in water is first increased and then diminished by the addition of alcohol ” I t is probable that some important fact has been omitted in this statement.
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“Owing to t,heir large surface, and their colloid character, the fibers readily adsorb dissolved substances from solution and also water. This adsorption is perhaps mainly due to the simple surface action, but it is partly of the more profound kind which occurs when a sol is neutralized by an electrolyte. It follows that a filter paper may not only remove soluble constituents from a solut,ion being passed through it, but it may be extremely difficult to wash these out again. Errors can obviously be caused in this way. The weight of precipitat,e obtained after drying or ignition may be too great, while values found for constituents subsequently estimated in the filtrate may be t,oo low. In extreme cases traces of substances may be entirely removed from solution by filter papers and so escape detection, though in suitable cases their removal by such means may be made the basis of a method for separating and eetimat,ing them. In cases where filter papers are used which are not of the ashless variety, disturbances may be caused by replacement of the inorganic constituents of the paper, which are probably present in the adsorbed condition, by ot,her substances, derived from tmhesolution being filtered. The correction subsequently applied for the ash of t8hefilt.er may then be wide of the mark,’! p. 923. “The adsorption effects noticed with ordinary impure adsorbents are frequently complicated by the impurities present. Thus with ordinary charcoal the ash constitaents play an important role. The same also applied to filter paper. According to Kolthoff the adsorption of acid by filter paper is almost entirely determined by the ash and due to chemical interaction between the acid and the mineral matter. Ash free paper or cotton wool hardly ndsorb any acid. Indeed from the experiments of Masters the tendency seems to be for it to adsorb the base from neutral salts and leave the acid. “In a somewhat similar way the adsorpt,ion effects observed with glass wool seem to be largely determined by t,he alkaline character of this material. Asbestos which has been carefully purified by treatment with acid practically does not adsorb positive ions whereas ordinary impure asbestos does and cannot safely be used as a filtering medium,” p. 92 j. “Scheringa found that, ferric hydroxide always carried down zinc when precipitat,ed hy caustic sodn-even if the zinc salt be added after t.he caustic soda. Precipitation with rold z j percent ammonia solution gave a complete separation. however, if ammonia of the same st#rengthwas used to wash the precipitate. “The well-known fact. that many hydroxide precipitates gradually become less reactive, and less readily soluble in acids, may well be due in part to some such process as that outlined for copper hydroxide, though not proceeding to such a degree of dehydration as in that case. There seems little doubt a t any rate that it is connect,ed with some loss of water either from t,he sol particles or from the gel. “A similar change seeme to be the cause of the instability of the eolutions of many hydroxides ( e . g., that of aluminium) in caustic soda, or in ammonia ( e . 9 . . chromium hydroside) or even in acids ( e . g., the slow hydrolysis of ferric chloride solutions) although the type of crystalloidal compound initially present in the solution is quite different in the t.hree cases. If the concentration and proportion of caustic alkali, ammonia or acid are not excessive, the metallic hydroxide molecules formed by hydrolysis gradually unite to form highly disperse sol particles which in time coalesce, undergo some dehydration, and ultimately separate in a relatively dense and unreactive condition. According to Fricke and Windhausen no dehydration occurs but only an increase in the size of particles when chromium hydroxide separat,es from caustic potash solutions,” p. 929. “The sulphides of analytical Groups I1 and I\‘ present several features which recall those found among hydroxide precipitates. They are so insoluble that their precipitation ie essentially a colloidal process and they adeorb large quantities of water. This tends t,o result in bulky gels built up of aggregates of very small particles. The water content of the precipitates IS variable and loosely held, which accounts for the difference in views as to whether they are hydrated sulphides or hydrosulphides or even partly hydroxides and hydrosulphides. Possibly all these compounds mag be present in different cases and under different circumstances. The tendency to lose water-and perhaps H2S too-seems to be even more marked among the sulphides than among the hydroxides, and with this is connected the remarkable difficulty with which the sulphides of cobalt, nickel and, to a less
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The hydrolytic dissociation of soaps is prevented by the addition of alcohols. “Hence the rule t,hat in tit,rat,ing fatty acids with aqueous alkalies, alcohol should always be present at, the end of the titration in a concentration of about fift.y percent,” p. IO. “The glycerides of fatty acids occur in animals stored in the connective tissue cells of adipose tissue which is found principally in the subcutaneous tissue, the bone marrow, beneath certain parts of t,he peritoneal, pericardial and pleural serous membranes, and in the interstitial tissue of the voluntary muscules. In this adipose tissue fat the glycerides are as a rule to a small ext,entesters of st,earic, to a larger extent of palmitic, and most of all of oleic a i d . In certain animals the glycerides of other fatty acids occur. In lard the liquid fatt,y acids have properties (iodine value, vide i n f r a ) which indicate that ten percent of the acids ent,ering into the composition of t.his fat are of the linoleic series (Twitchell). In the fat of the horse and the hare there is similar evidence for the presence of glycerides of other acids. I t is further remarkable that, in certain species, the fat of animals kept in captivity differs from that of those living wild. The evidence that points to the presence of linoleic acid esters in the fat of t.he domesticated pig points to there being more of such esters in the fat of the wild boar. And the same difference is particularly well marked in the rabbit (iodine value of fatty acids from tame rabbit 64, from wild rabbit I O I ) , and t,he duck (iodine value of fat of tame duck 58, of wild duck 85). “On the other hand, this difference does not appear t,o hold for the cat, and the character of the fat of the chamois and deer living in freedom (iodine value 25 to 30) does not justify generalisations from the facts mentioned,” p. 37. “The changes undergone by fats and oils when they become rancid are probably initiat,ed or favoured by enzymes and hydrolyse the glycerides. The free fatty acids are then oxidised by the oxygen of the air in t,he presence of traces of moisture. But the part, played by enzymes and also by the action of light is a subject of some dispute. The changes consist in ( I ) the appearance of hydroxyl acids and (2) of lower volatile fatt,y acids, their esters or aldehydes; (3) the hydrolysis of the fat; and (4) the disappearance of the 1iberat.ed glycerol. “The more saturated acids the fat cont,ains, the less liable is it to become rancid; cacao butter, for instance, is rarely found t’o undergo this change. The presence in a fat of other substances on which bact,eria can grow increases the probability of rancidity; butter, for instance, is particularly prone t o the change. But a sterile fat may nevertheless become rancid; and as Duclaux showed, the growth of bacteria in an impure fat. though it may promote a tendency t o rancidity, is not the cause of the change. The taste of rancid fat is probably due to the formation of oenanthal and pelargonal from palmitoleic and oleic acids,’’ p. 43. “The formation of fat being a process of fundamental import,ance to animals and plants, it, does not seem unlikely that the process in ite essentials may be the same in bot,h. This proof of the r61e of carbohydrates in the animal proccss strengthens, therefore, the less direct results which have been obtained with plants, which, it, may be recalled, also indicate that, in the vegetable kindgom, carbohydrates form the starting point in the synthesis of fats. “The carbohydrates and fats differ so widely in their chemical characters and composition t,hat it is unlikely that the whole of the processes of transformation of the former into the latter mould be easily demonstrated experimentally. I t is not surprising, therefore, that direct evidence of a transformation of carbohydrate into fat has so far not been obtained in any isolated organ. Leat,hes and Hildesheim (1904 and 1908) however, have shown definitely that the liver participates in the process and certainly in its later stages,” p. 1c8. “Before passing to the discussion of the origin of glycerol one other matter awaits considerat.ion, namely, the possible formation of fat from amino acids. Since certain of the naturally occurring amino acids have been shown to be capable of transformation into glucose in diabetic animals, it is reasonable to suppose that t8heymay also be converted into fatty acids because glucose is capable of this change. Nevert,heless, as indicated earlier in this chapter, protein, which is built up from amino-acids, has, so far, not been proved to give rise to fat formation in the body. The reason is probably to seek in two directions.
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difference between the two routes means that fat absorbcd by the blood will go through the liver before it reaches ot.her tissues, and that which goes by the thoracic duct will be distributed equally to all part,s. The readiness with which the liver in certain circumstances takes up fat. may make the lacteal route advant,ageouswhen fat is to be laid by in adipose tissue,” p. 143. “The way in which the reserve of fat is put into circulation and conveyed to the organs where its energy is to be liberated is very little understood. From the consideration of bhe facts mentioned, a st’arvingman must be able to draiv on fat stored in his adipose tissue to the extent of something like zoo grms. a day, or perhaps 200 mgrms. a minute during the waking hours. His blood, or the blood of normal men (Bloor’s average from t,welve) contains the amount of fatty acids corresponding to 200 mgrms. of fat in almost exactly gc C.C. or perhaps one-hundredth part of the whole circulating blood. In one minute therefore the t’ransport of fat in such conditions, when by hypothesis 90 percent of t’he energy is derived from fat mobilised from adipose tissue, represents a turnover of something like on? percent of the total amount of fatty acid present in one form or another in the R-hole blood. It is necessary t o visualise this, because otherwise there is a t,emptation to think that it should be very easy to demonstrate any extensive physiological mohilisat ion of reserve fat by analysis of the amount of fat in a sample of blood taken from any accessible vein. The temptation may be escaped, moreover, also by the reflection that a physiological mohilisation of fat is presumably brought about by some reaction due or corresponding to the avidity of working cells for fat-the faster the fat is t,hrown into the blood, the faster it ~villbe removed by hungry cells. If the adjustment is delicate it would be logical to expect the amount of fat, in the mixed blood to be unchanged; if it is not’, then at some moments the amount, of fat must be above, but at others beloiv the normal value, and there is nothing to indicate how the desired figures are to be obtained. It is indeed remarkable how often they have been,” p. 154. “Animals use fat primarily as a source of energy. This does not mean that, fat is only of importance to the animal as a source cf energy, for, as pointed out in the following chapter, fatty acids in one form of combination or another are indispensable constituents of ‘animals and when the quantity in the body is reduced by inanition below a certain minimal figure. death ensues. I t is, however, true to state that the greater part of the fat, which is taken daily as food is utilised for the liberation of energy as heat and work. Were this fat simply stored, animals would gain in weight very rapidly and in a short space of time resemble bladders of lard. This self-evident truth, that the bulk of the fat taken by an animal is oxidised and not stored up is supported by evidence gained from a study of the gaseous exchange on different diets,” p. 175. “AndrB Mayer and his fellow-workers then have done much to substantiate the conception of cell protoplasm that Hoppe Seyler, and Hermann, indicated many years ago. Protoplasm is not merely an old word for a solution of prot,eins; nor are t,he phenomena of life manifested merely in a colloidal solution of proteins in which certain elect,rolytes and certain reserve food-stuffs play merely subsiduary parts. Prot,oplasm is a complex equilibrated system in which, side by side, with colloidal solutions of proteins, fatty components together with cholesterol, though quantitat.ively less in amount, play a r61e which it is impossible to say is less essential than theirs. “Andr6 Mayer, moreover, thinks that this system has for each type of cell a composition characteristic for that type, and that the proportion in which the components occur in the protoplasm determines its behaviour. His estimations of wat,er, total solids, total fatty acids, phosphorus associated with fatty acids and cholesterol in the different organs, are an attempt to define the characteristics of the protoplasm of these organs. If only he could include determinations of the amino acid groupings in their proteins, their chemical pattern and molecular structure, his att,empt would bring us nearer the truth; but, with these, he is, in these studies, not concerned. The relation which he finds, however, between the ‘lipocytic coefficient.’ and the amount, of water held by the liviiig cells of each organ, is an interesting illustration of his thesis. The lipocytic coefficient, the proportion that is between cholesterol and fatty acids, is higher in the corpuscles than in the serum, in the serum
