Suitable non-aqueous titration methods have been developed for the determination of total carbon in silicate and carbonate rocks, stony meteorites and metallurgical samples by a high-frequency induction furnace. The method has been extended to the determination of carbon dioxide in rocks, clay and limestones by the acid evolution method. A conventional receiver with a buret for continuous titration was unsuitable in the induction heating procedure; and was replaced by two connected borosilicate glass receivers in a closed system. Acetone either alone (for 0–10 mg C) or in 1:1 mixture with methanol (for 10–30 mg C) containing 0.6% ( v v ) monoethanolamine and an excess of standard sodium methylate was found to be a better absorbent for carbon dioxide than pyridine. After reaction, the excess sodium methylate was back-titrated by a standard methanolic solution of benzoic acid with phenolphthalein as indicator. The method gives reliable results up to 47 % total carbon dioxide.