The removal of radon from CO₂ for use in¹⁴C age measurements

Summary

It is shown that traces of radon can be extracted from carbon dioxyde by pumping off from solid CO₂. Since the volatility of radon is smaller than the volatility of CO₂, special care has to be taken during condensation in order to avoid occlusion. Enrichment of radon at the wall where the CO₂ condenses is avoided by stirring the gas. An estimate of the fraction of radon, adsorbed on the wall, demonstrates the necessity of performing the condensation at about 80°C. At 180°C the greater part of the radon is adsorbed; consequently it is occluded if CO₂ is added. The method can be used only in those cases where the volatility of the contaminant is not too much lower than of CO₂, and where the molecules of the contaminant do not fit well into the lattice of solid CO₂. The present purification is much faster than the chemical purification described previously¹)²).