AbstractThe electronic absorption spectrum of orcein is studied in organic solvent of varied polarities and water‐organic solvent mixtures with differentpH. The absorption bands are assigned and the effect of solvent polarity on their position is discussed. Thepkaof the acid‐base equilibria set are determined and commented upon in relation to nature and proportion of the organic solvent added. The main bands of the ir spectrum and signals of the1H nmr spectrum are as well discussed. The mixing of orcein with transition metal ions leads to drastic changes in colour and hence the visible absorption spectra of both organic compound and metal i