SCIENCE
THEORETICAL AND APPLIED COLLOID CHEMISTRY. By Wolfgang Ostwald. John Wiley & Sons and Chapman & Hall. 11s. 6d. net.
THE CHEMISTRY OF COLLOIDS. By Richard Zsigmondy. John Wiley & Sons and Chapman & Hall. 13s. 6d. net.
Colloid chemistry, for which Dr. Wolfgang Ostwald claims to have established the right "to existence as a separate and independent science," is a study of very recent development, which has come to its own during the past twenty years. In many respects its development offers a close parallel to that of catalysis, a branch of chemistry recently noticed in these columns. In both cases we have a few brilliant, isolated studies, succeeded by a long period during which little attention was paid to the subject; in both cases this century has seen a large body of chemists, especially the younger men, attracted to the investigation, the phenomena in question, and results have been rapidly attained which have proved of great theoretical interest, and have already found wide application in industry. Just as the old idea that there were a few special catalysts has been succeeded by the belief now held that every substance can be made to act as a catalyst in suitable circumstances, so it is now stated freely that, instead of there being a small class of colloids, any substance can be prepared in a colloid state. Incidentally, colloidal preparations are widely used as catalysts.
Colloid chemistry may be said to have arisen some fifty years ago in the researches of Thomas Graham, who showed that a large class of liquids or semi-liquids would not diffuse through animal membranes, as do ordinary solutions of salts. Because many of these substances were sticky he gave to the whole class the name which they now hold, colloid. Since then his conception has been extended, and it is now realised that, strictly speaking, we should talk rather of a substance in a colloidal state than of a colloid, since typically crystalline substances, such as ordinary salt, can be prepared in colloidal solution. The characteristic of such a solution is the fineness of sub-division—the dispersion—of the "dissolved" substance. In a true solution, in the ordinary sense, we have, in general, the substance existing as separate molecules dispersed throughout the solvent. In a mechanical suspension, such as may be prepared from exceedingly fine sand and water, the suspended particles, which take some time to settle, can be easily seen with a microscope, if not with the naked eye. In between these two classes of dispersed systems we have solutions in which the particles, while consisting, in general, of a very large number of molecules, are small enough to pass through filter-paper and escape the ordinary microscope, while at the same time they do not diffuse through membranes and can be seen by special optical arrangements, i.e., the so-called ultramicroscope. Such dispersed systems are colloidal systems, which have only recently been investigated in detail, although Faraday prepared colloidal solutions of metallic gold which still exist. Colloidal chemistry has been picturesquely called "the world of neglected dimensions," which is appropriate enough. Of course the exact degree of dispersion which constitutes a colloidal solution is purely arbitrary, since, as Wolfgang Ostwald—the son of Wilhelm Ostwald—insists in the book before us, solutions are known which show all ranges of sub-division of the dissolved substance, from molecular dimensions to visible particles. Various distinguishing tests have led to solutions in which the diameter of the particles lies anywhere between a millionth and a thousandth of a millimetre being conventionally called colloids.
The scientific, industrial, and medical applications of colloid chemistry increase in number daily—we are already confronted with the word colloidotherapy—and there is a growing demand for books on the subject. The two before us are each by authors who are celebrated for their researches in the subject: Zsigmondy invented the ultramicroscope, which has been responsible for the most important recent advances in the study of colloidal solution, and Wolfgang Ostwald has added clearness to nearly every branch of the subject. Ostwald's book, adequately translated by Dr. Martin Fischer (although, we may remark, the word "enormity" is not generally used as a synonym for hugeness), is based on a series of lectures given by him in America just before the war. Publication has been delayed by the war, and it is interesting to note that in the preface, written in 1915 when Germany was apparently in a good position, the author looks to science to form the first bridge between the peoples then at war, and exclaims, "How should I, for example, cease to admire, to adopt, and to develop the labours of a W. B. Hardy, a W. M. Bayliss, a J. Perrin, a P. P. von Weimarn, and others, just because they belong to a people hostile to my own?" The book gives a most excellent sketch of the whole field, by one who is an enthusiast in his subject, and may be thoroughly recommended as an introduction for those who are beginners, even if their general knowledge of chemistry is slight, while even the expert will find much in it to interest him. As a detail we may mention that Ostwald gives a quick receipt for the preparation of red colloidal gold with ordinary distilled water, while other authors, including Zsigmondy, insist that the preparation is a delicate undertaking, requiring specially distilled water and the greatest care. The wonderful range of phenomena now included in the subject is clearly brought out, and the pictures of Liesegang rings and the ultramicroscopic photograph of a setting cement are beautiful. The treatment of gels, the jelly-like form into which certain colloidal solutions pass, is particularly good, and gives much valuable information not hitherto available in popular form. The last two chapters, or lectures, on scientific applications and technical applications of colloid chemistry are of surpassing interest, as indicating the practical importance which this young science has attained. All life processes take place in a colloid system, and the necessity to physiologists of the study of colloids is forcibly emphasised. Rubber milk, or later, is a colloid, so that all the problems of coagulation of rubber and its subsequent vulcanisation are included in the subject. The setting of cements is a colloidal problem. These, and many other questions, are briefly but clearly discussed. The experiments which accompanied the lectures are described, and are most suggestive.
Professor Zsigmondy's book is more technical, and deals mainly with "hydrosols" and "hydrogels." The author's reputation in this field vouches for the excellence of the treatment of the many expert problems discussed. Naturally the subjects of ultramicroscopy and protective colloids are discussed in detail—the author originated the "gold figure" used to express the protective effect of a colloid. The theoretical discussions are particularly valuable, and physiologists will read with interest the long discussion of protein bodies. There is an appendix on industrial colloid chemistry by the translator, Dr. Ellwood Spear, in which the problems of rubber manufacture, tanning, and other industrial processes are very briefly treated. There is in this section a chapter on smoke abatement, but the methods mentioned scarcely fall within the province of colloid chemistry as generally understood. A final chapter, by Dr. J. F. Norton, deals with the application of colloid chemistry to sanitation.
MODERN SCIENCE AND MATERIALISM. By Hugh Elliot. Longmans. Green & Co. 7s. 6d. net.
This book is an exposition of monism, the philosophic theory that asserts the identical nature of mind and matter, as distinct from the dualistic "superstition"—as our author terms it—of matter and spirit. Sir Oliver Lodge, in a recent article, claims that three fundamental things are required to explain our universe: viz., Mind, with its rudiment Life; Matter, with its element the electric charge; and Ether, with its fundamental properties equivalent to elasticity and inertia. Mr. Elliot will have none of this. For him there is no reason to postulate other things than those capable of investigation by physical science—the ether and matter are essentially of the same kind, while all the phenomena of life are, if not at present explained on a physico-chemical basis, yet ultimately explicable in terms of the exact sciences. Life is a name for certain properties of protoplasm, and the chemical reactions of life are more complicated, but not more mysterious, than those of the laboratory. As for "ghosts, gods, souls, et hoc genus omne," our author holds that "these have long been rejected from the belief of most advanced thinkers." He traverses the assertion of Professors Mach and Karl Pearson, that while science can explain "how" things occur it cannot explain "why" (the point under discussion depends, of course, on Mr. Elliot's interpretations of the words), he pours scorn upon Herbert Spencer, Bergson, and all the vitalists. Altogether the book is one of the most pugnacious defences of monism which we have read, and will delight the bitter opponents of all spiritualistic philosophies. At the same time the author maintains that his philosophy is not materialistic, in the ordinary sense, but a form of idealism, and this, of course, is true, in a way, of any form of monism, it being possible either to say that the atom of matter is as full of mystery as life, or that life is as full of mechanism as the atom. It is obviously impossible in the limited space at our disposal to criticise the arguments put forward on a subject so complicated and controversial, but we think that nobody will admit Mr. Elliot to be as unbiassed as he appears to consider himself, judging by his remarks on the bias of the vitalists. His claim for the support of the physiologists reminds us that Dr. J. S. Haldane recently opened a discussion on the question, "Are Physical, Biological and Physiological Categories Irreducible?" by a pronouncement in the affirmative; the physicists also are not all monists. The question is more two-sided than our author will admit. His science is unfortunately by no means beyond reproach: to say that the charge on the electron is "inconceivably immense" is either extraordinary inaccuracy of phrase or extraordinary error, while to state that the electron has weight is to assert something of which we have no experimental evidence. That light is a vibrating motion of the same character as sound is incorrect, and such instances can be multiplied. These things are not of fundamental importance to Mr. Elliot's argument, but they show, to say the least, a deplorable looseness of expression. Nevertheless, the book is worth reading to all interested, either as friends or enemies, in the monistic philosophy, and may lead some of those who talk so freely of souls and mind to be a little more precise as to what they mean by these terms.
ACCOUNTS RENDERED OF WORK DONE AND THINGS SEEN. By J. Y. Buchanan. Cambridge University Press. 21s. net.
Selections from the papers of the author have already appeared under the titles of Scientific Papers (Oceanographical) and Comptes Rendus of Observation and Reasoning. This third volume, with an English modification of the title of the latter work, continues the plan of that book. The papers are very varied in character, including chemical studies, accounts of physical determinations, addresses on geography and oceanography, more technical geographical writings, and short articles on topics of general interest, reprinted from Nature, the Times, and other periodicals. Many of the latter recall events of our generation important, but already half forgotten, such as the stranding of the Sultan and the wreck of Santos Dumont 6. An excellent feature of the author's Comptes Rendus was the detailed summary, with page references, provided for every article, and the same plan is followed in this work. The author's work on oceanography is too well known to need commendation—he was chemist and physicist to the Challenger expedition. His "Retrospect," the second article in the book, gives a fascinating summary of the work done on that expedition, and the other papers on oceanographical subjects are of great general interest, and incidentally recall the great services of the Prince of Monaco to that science. His general outlook, which lends such freshness to all his writings, cannot be better expressed than in his own words in a former book: "It was conveyed to me through an old friend and former colleague that this contribution
... had done much to retard the standardisation of research. I took it as a compliment.
To standardise research is to limit its freedom and to impede discovery. Originality and independence are the characteristics of genuine research, and it is stultified by the acceptance of standards and by the recognition of authority."
It throws much light on the recent increase in the expenses of publishing that, whereas the Comptes Rendus was published in 1917 at 7s. 6d., the present volume of similar size and form is published at 21s.