The Use of the Exchange Between Carbon Dioxide, Carbonic Acid, Bicarbonate Ion, and Water for Isotopic Concentration

A study was made of the exchange of oxygen and carbon in the reactions: $$\begin{array}{c}{\mathrm{CO}}_2(\mathrm{dissolved}\mathrm{)+}{\mathrm{H}}_2\mathrm{O}\rightleftarrows {\mathrm{H}}_2{\mathrm{CO}}_3,\\ {\mathrm{CO}}_2(\mathrm{dissolved}\mathrm{)+}{\mathrm{OH}}^{-}\rightleftarrows {\mathrm{HCO}}_3^{-}.\end{array}$$ It was found that the rate of the first could be increased four or five times and the rate of the second up to 2000 times by heterogeneous catalysis. Investigation of the use of these catalyzed reactions for separation of the oxygen and carbon isotopes was carried out both by the use of a static bomb technique and by the operation of fractionating columns. The effects of different operating conditions were indicated, and the necessity for turbulent flow in the gas phase was established. Pressures from one through fifty atmospheres were tried, as the increase of CO₂ pressure increases the concentration of CO₂ (dissolved) and thus speeds up the exchange. A comparison of the above method with the HCN – CN⁻ method of separation of carbon isotopes shows the cyanide exchange to be somewhat faster and to require less time to come to production, somewhat doubtful advantages when they must be coupled with the polymerization and poisonous properties of the hydrogen cyanide, as well as with its greater cost.