The pronouncement of August, 1917, the Montagu-Chelmsford Report, and the passing of the Government of India Act of 1919 are first steps towards the establishment of self-government for India; but the real difficulty to be solved is the representation of the mass of the people. Mr. Macdonald holds that "The democratic forms of the West are not the only forms in which democracy can take shape.... India is not a nation of equal citizens so much as an organisation of co-operating social functions." The question of diversity of race and language will remain even when primary education has become general, and Mr. Macdonald might have made clearer his views of the lines on which genuine popular representation can be secured. He does, indeed, in his account of the 50,000,000 "outcastes" of India give us a dim vision of his hopes that with education will come leaders of ability to represent them; but this does not solve the main problem of ascertaining and giving expression to the will of the people. With the Councils and reformed administration India will be somewhat in the position of England in 1832, and whether she is to develop under British tutelage, or to be left to work out her own salvation under her own bourgeois Government, is a question which statesmen will be called on to decide in the near future.
The chapters on finance and on religion and Nationalism are among the best in the book, while the pithy accounts of the ceaseless toil of a Lieutenant-Governor and of a District Officer should disabuse the minds of those who have been accustomed to regard Indian civilians as comfortable overpaid loafers.
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.