The Problem of Physico-Chemical Periodicity

Abstract

THE normal chemist is so well used to seeing This reagents pass away in a decently continuous fashion, that when he finds them attacking each other in a succession of recurrent spasms, he is a little apt to shy off. The thing is, perhaps, too nearly suggestive of heart-beats, of vital processes, and of human activities: domains into which chemists are warier of intruding than formerly, and which they prefer to leave to their bolder brethren, the physiologists and the historians. At all events, rhythmic, pulsating, or periodic reactions have seldom been systematically followed up in any general way by chemists. There have been, it is true, such detailed inquiries as Ostwald's on the periodic dissolution of a specimen of chromium in acid, as Bredig's on the pulsating decomposition of hydrogen peroxide by mercury, and as the numerous studies of the Liesegang effect in jellies; but Dr. Hedges and Dr. Myers have now worked their way to a more comprehensive survey than these, which they have summarised in a small monograph. The broad plan of this is, first to classify periodicities of various sorts, then to set forth the experimental factors that operate in each class, and to give in the end an indication of the views which the authors-themselves notable experimenters in the field-have formed as to underlying causes. The full and important bibliographic index contains about 300 references, of which about one-third centre in the Liesegang phenomenon. About twenty fall outside the last thirty years.

The Problem of Physico-Chemical Periodicity.

By Dr. E. S. Hedges Dr. J. E. Myers. Pp. 95 + 2 plates. (London: Edward Arnold and Co., 1926.) 7s. 6d. net.