Abstract: A method for the determination of total carbon, calculated as carbon dioxide, present in aqueous solutions containing organic compounds and/or inorganic carbonates by mixing the aqueous solution with a solid reagent active at elevated temperature for the displacement of carbon dioxide from inorganic carbonates, contacting the mixture with oxygen at elevated temperature whereby carbon dioxide is produced by oxidation of organic compounds and by displacement from any inorganic carbonates present, drying the carbon dioxide so produced, separating the carbon dioxide from the oxygen by selective adsorption on a bed of particulate adsorbent which preferentially retards the passage of carbon dioxide, flushing the bed with inert gas to displace the oxygen, thereafter eluting the carbon dioxide by raising the temperature and reversing the flow of inert gas through the bed and finally measuring the eluted carbon dioxide.