The combination of conventional thin-layer chromatographic techniques with a novel form of column chromatography has enabled seventeen derivatives of coumarin in used nickel-plating solutions containing this additive to be isolated. Ten derivatives were identified, as mono-, di- and trihydroxycoumarins and dihydrocoumarin, melilotic acid, o-coumaric acid and umbellic acid. R_F values and colour reactions of twenty typical coumarin derivatives are also reported.