Photochemistry in Retrospect

Abstract

PHOTOCHEMISTRY now appears to be a well-established science with a highly developed technique of its own and an adequate foundation of theory, based largely on indisputable facts established by the molecular spectroscopist. Recent text-books¹ leave the reader in no doubt as to the correct avenues of approach to this subject. Its devotees must be prepared to undertake the detailed study of absorption spectroscopy, reaction kinetics, the behaviour of free radicals, and the electronic transitions in solids, some of which are still largely unexplored fields. The more serious student, however, will be disappointed to find that the historical approach to photochemistry has been greatly neglected in these books, excellent as they are in other respects. In the historical treatment of a science interesting sidelights are often shed on scientific method, and the lessons we can learn from them are of peculiar value. For example, it would be instructive to reveal why certain lines of investigation were dropped, how some apparently slight but fundamental observations led to developments of the greatest magnitude, why a fundamental law universally acclaimed and applied appears now to be worth only passing consideration. Photochemistry in particular., which has reached the greater part of its present stature within the last twenty years, has some interesting things to reveal which come within these categories.