Electron Affinity of Positronium

By use of the variational method as previously applied to the mathematically similar problem of the negative atomic hydrogen ion, the energy of a compound of two electrons and one positron has been calculated. The resulting (third approximation) value of roughly 0.19 ev binding energy of this system with respect to dissociation into a free electron and a system of one electron and one positron corresponds to the value already found by J. A. Wheeler. On the basis of higher approximations obtained for ${\mathrm{H}}^{-}$ the exact binding energy of the tri-electron has been estimated to be 0.203 ev.