The Radioactivity of Potassium

Abstract

THE work of Aston has shown that potassium, which has an atomic weight of 39·104 (Hönigschmid), is a mixture of two isotopes. The atomic masses of these are 39 and 41, and they are present in ordinary potassium in the proportion of 20 to 1 respectively. Potassium emits a fairly penetrating β-radiation, and we are led to inquire as to which of the isotopes iS responsible for the emission of β-rays. It may be that there is a third isotope present in potassium, but in such small amounts that its detection by the mass spectograph is impracticable. Such a possibility has been discussed by Harkins (Proc. Nat. Acad. Sci., vol. 11, p. 630; 1925), who considers that isotopes of mass 40 or 41, the former of which is unknown, are the ones most likely toe radioactive. Harkins considers the hypothetical isotope of mass 43 (Kossel: Phys. Zeit., vol. 20; 1919) to be less probable.