The determination of water in lubricating oils by a near-infrared spectrophotometric method

Abstract

The water content of clear mineral oils can be quickly and accurately determined by dissolving the wet oil in ethyl acetate and measuring the near-infrared absorbance of the solution, relative to a similar reference solution previously dried by molecular sieves. In discoloured or cloudy, wet oils the water can be removed by azeotropic distillation with ethyl acetate, and the water content of the distillate determined spectroscopically. With the latter procedure, errors that arise at low water concentrations may be due to the absorption of atmospheric moisture by the solvent.