USE OF QUINIZARIN AS A SPECTROPHOTOMETRIC REAGENT FOR MGO CONTENT-ANALYSIS OF PORTLAND-CEMENT AND CEMENT CLINKER

A new direct spectrophotometric method for the determination of magnes ium oxide in Portland cement and cement clinker is proposed. The metho d is based on a reaction with quinizarin (QUIN 1,4-dihydroxyanthraquin one) in ethanol-water (50% v/v) solution at pH = 9.5-10.3. Under optim um conditions, the determination of 0.5-3.9 mu g.ml(-1) of magnesium i s possible. The method is rapid and selective and possesses good accur acy and precision. The analysis of cement materials of variable magnes ium content is feasible over the concentration range of 0.85-3.2 mu g. ml(-1) Mg; the detection limit is 25.3 ng.ml(-1) Mg. Under the given c onditions, no constituents normally present in Portland cement materia ls interfer. The procedure was tested by analyzing several standard re ference materials and real samples of Portland cement and has been fou nd to give satisfactory results. It has been satisfactorily applied to the determination of magnesium in clay and raw meal.