General principles

Abstract

In this introduction to a discussion of the principles of circular dichroism it is appropriate to recall that our meeting is the third of its kind to be held in the rooms of Burlington House. The previous discussions took place in 1914 and 1930 on the general topic of optical rotatory power, and the proceedings of these meetings (Fara­day Soc. Disc. 1914, 1930) provide us with a general conspectus of the classical discoveries and unresolved problems from which the more recent advances in large measure derive. The 1914 meeting marked the approximate centenary of the discovery of optical activity (Biot 1817) and it followed the then relatively recent deduction of the tetrahedral orientation of the valence bonds of carbon (Le Bel 1874; van’t Hoff 1874) and the octahedral structure of transition metal complexes (Werner 1911) from the stereochemical requirements of optical isomerism (Pasteur 1848). Only a few years earlier circular dichroism in liquids had been discovered by Cotton (1895) and the first of the classical electromagnetic theories of optical activity had been put forward by Drude (1892).