System and method for determining acid content in lubricants

A system and method of characterizing an at least partially hydrophobic sample. The method includes providing an ethanolic solution of ethanol and sodium hydrogen cyanamide, adding a first portion of the ethanolic solution to a sample to produce a reagent-sample mixture, performing infrared spectroscopic testing of the reagent-sample mixture to generate mixture absorption data representing at least one absorption characteristic of the reagent-sample mixture, and generating acidity data for the sample based on the mixture data. The system includes a cell for holding and evaluating a sample which is mixed with an ethanolic solution to create a reagent-sample mixture, an infrared spectrometer for measuring light absorption characteristics of the reagent-sample mixture, and a computer equipped with software for analyzing data outputted by the infrared spectrometer and utilizing an empirical model to derive at least one universal calibration equation relating data representing the light absorption characteristics of the reagent-sample mixture to acidity of the sample.