Calculations of the ionization density resulting from β-ray fluxes produced by the decay of UX2 (Pa234m) using constant-cross-section transport theory agree with experiment to better than 5%. The ionization densities were measured using an extrapolation chamber and a thin-walled ionization chamber. The experimental β-ray absorption coefficients reported in 1931 by the International Radium-Standards Commission can be calculated to better than 15% using the same theory.