PROF. G. VON HEVESY, of the University Institute for Theoretical Physics, Copenhagen, has been awarded the Nobel Prize for Chemistry for 1943. Prof. von Hevesy's earlier work was mainly in the field of radioactivity and radioactive isotopes. He determined the valency and electromotive series of the radio-elements, and established the identity of radium D with lead. Investigations on the 'self-diffusion' in liquids and solids introduced the use of radio-elements as indicators in following the movements of common elements with which they are isotopic, and this technique he has developed in chemistry, physics and biology, where the use of 'tracer elements', which now include artificial radio-elements, has become very important in the elucidation of reaction mechanisms, and in following the processes of metabolism. Prof, von Hevesy's most recent work is in this field. His work with Brönsted on the separation of isotopes of mercury and chlorine by diffusion has become classical.