A method based on the decoloration of dilute chloroform solutions of ura nyl quinolin-8-olate by shaking with aqueous solution of anions is proposed for the spectrophotometric determination of carbonate. The effects of several variables on the decoloration (pH, shaking time, volume ratio, etc.) were established. The spectral stability of an organic solution of the metal chelate is increased with an excess of quinolin-8-ol in the organic phase, and it avoids its stripping with water. The decoloration of chloroformic solutions varies linearly with the carbonate concentration between 10 and 50 μg.ml−1in the aqueous phase (apparent molar absorptivity is found to be 2.03×103l.mol−1.cm−1at 390 nm). Interferences of many foreign ions (cations and anions) are also established. The method is relatively free from anion interferences.