Abstract The CO 3 - radical is produced in the pulse radiolysis of N 2O containing carbonate solutions (1–6) (1) OH + CO 3 2- → OH - + CO 3 -. Although it is known that it disappears via mutual deactivation with 2 k = 1.5 × 10 7 M -1 S -1, the products of this deactivation have not yet been unambiguously recognized. In the previous pulse radiolysis work, only optical absorption measurements were carried out to trace the short-lived intermediates. In the present work, the conductivity changes that often accompany the changes in optical absorption of irradiated solutions, were recorded also. The a.c. method used and the evaluation of the data have been described earlier. (7,8)It is shown that CO 3 - radicals react with each other and with other radicals such as NO 2 and SO 3 - via the transfer of an O - ion. The resulting CO 2 was detected by the conductivity changes that accompany its reaction with water. Reaction of CO 3 - with CH 3 proceeds through a long-lived complex.