The relative abundances of nuclei are often supposed to be related to nuclear stability. We may consider stability in two ways: on the one hand stability may refer to a mixture in thermodynamic equilibrium; or, on the other it is often used when referring to a system characterized by a slow rate of change to a thermodynamically stable state. It appears possible to test the hypothesis of equilibrium by a number of transmutation reactions. We restrict ourselves to those reactions in which the same elements, differing only in mass, occur on each side of the equation, and find that the thermodynamic calculations become very simple. The calculations are in agreement with the assumption that the atomic nuclei on earth do not represent an equilibrium mixture at any temperature.

• Received 20 June 1931

DOI:https://doi.org/10.1103/PhysRev.38.718