A method based on the decoloration produced in organic solutions of coloured complexes when they are shaken with aqueous solutions of anions is proposed for the spectrophotometric determination of sulphide using dilute chloroform solutions of copper quinolin-8-olate. The effects of several variables on the decoloration (pH, shaking time, volume ratio, etc.) were established. The method is very sensitive (the apparent molar absorptivity a t 410 nm is 2.35 x lo4 1 mol-1 cm-l) and can be used for determining sulphide in the presence of other sulphur anions. Trace amounts of sulphide in water were determined spectrophotometrically and the results obtained were compared with those obtained using the methylene blue method.

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The electroanalytical behaviour of orotic acid in cathodic processes has been studied in HC1Oa, at several pH values in Britton-Robinson buffers, using DPP and CV techniques.Orotic acid undergoes three cathodic waves over the entire pH range considered. Optimum conditions for determination of orotic acid using the DPP technique are also studied.