A method for the determination of the cross-section ratio a_ ~o/(a_ 11-~-o" 10) for hydrogen ions in gases is described; the indices refer to the initial and final charge state. The method is based on the fact that a polarized hydrogen ion beam loses a certain amount of its initial polarization during charge exchange from the negative to positive state in the stripper canal of a tandem accelerator. Combined with the beam-attenuation method the individual electron-stripping cross sections o-11, a-lo and ao~ can be obtained.