Heavy Water in Chemistry

Abstract

THE lecture by Prof. Polanyi which is published as a Supplement to this issue of NATURE directs attention to some of the applications which may be made of heavy water in elucidating the mechanism of chemical reactions. The heavy water may be either the variety containing heavy hydrogen in place of ordinary hydrogen, or that containing heavy oxygen in place of ordinary oxygen, and the distribution of the heavy atoms among the products of reactions will indicate the part played by water in them. The striking difference in chemical properties between heavy hydrogen and ordinary hydrogen is due very largely to the differences in zero-point energy, which Prof. Polanyi calls permanent energy, the existence of which is predicted by the new quantum theory. It is possible to calculate this energy, and the results of the calculations may be checked by measurements of equilibria in which the two sorts of hydrogen participate. These experiments are in agreement with the theory. Exchange of heavy hydrogen from heavy water may occur with other compounds, such as benzene, and the mechanism of hydrogenation in ordinary reactions can also be followed in such experiments. The use of nitrogen and carbon isotopes is likely to prove important in the future.