The direct determination of additive metals in lubricating oils by complexometric titration. Part I. The determination of barium, calcium, lead and zinc

Abstract

Methods are described for the determination of additive metals in unused lubricating oils by complexometric titrations. The oil samples, dissolved in a toluene-isopropyl alcohol mixture, are treated in the presence of aqueous buffer with excess of EDTA. The unreacted EDTA is back-titrated with a standard magnesium solution in the presence of Eriochrome black T indicator. Zinc can be titrated directly with EDTA with methylthymol blue as indicator.

The results are compared with those obtained by established procedures.

The accuracy of the complexometric methods is comparable with that of established methods, but they are often ten times as fast and are, therefore, ideally suited to blending control.