Chemical, physical, and lubricant properties of magnesium stearate

Three batches of commercial magnesium stearate were characterized in terms of their fatty acid composition, moisture content, and specific surface area. None of these variables appeared to have any effect on the lubricant activity of the samples. The lubricant properties of the compound were further examined using three hydrates of laboratory-prepared (pure) magnesium stearate. Based on the results obtained from the pure samples, it appears that differences in the lubricant properties of magnesium stearate are correlated with differences in moisture content and crystalline structure.