The chemical exchange reaction between amine carbamate and CO2has been investigated for the purpose of using it as a practical method to concentrate13C. The effects of solvent, concentration of amines, catalysts, flow rate, and diameter of the column have been studied for a number of amines. Of the solutions studied, di-n-butylamine (DNBA) in triethylamine (TEA) as a solvent proved to be the most favorable for use in the preparation of highly enriched13C. The overall separations obtained as a function of the concentration of DNBA using 2.5 cm i.d. × 100 cm column ranged from 2.05 at 1Mto 1.69 at 2.84MFor 2MDNBA the maximum separation was 1.94. At this concentration of DNBA the overall separation as a function of flow rate ranged from 1.94 at 0.845 ml/cm2-min to 1.31 at 2.9 ml/cm2-min. Neither the rate of exchange nor the overall separations were improved by use of catalysts. Increasing the diameter twofold resulted in little or no loss in overall separations. On the basis of the properties of the system and the data obtained with respect to the above variables, design calculations were made for a six-stage tapered cascade. These calculations were based on a flow of 40 ml/min of 2MDNBA in TEA, giving a maximum transport of 7.1 × 10−3mmole/min or a maximum production rate of 130 mg13C/day. The cascade was operated for about 5 months during which period gram quantities of 67%13C were produced.