EVALUATION OF PARTICLE-SIZE DISTRIBUTION AND SPECIFIC SURFACE-AREA OF MAGNESIUM STEARATE

The geometric mean diameter and several other particle size distribution parameters of nine lots of magnesium stearate from Mallinckrodt Inc. and one lot from Witco Corporation were determined using a light scattering particle size analyzer. Similarly, the specific surface area of these lots was also determined using both single and multi-point B.E.T. methods. A regression analysis of the data indicated that there was a good correlation between the specific surface area and the geometric mean diameter of the various samples. Also, the volume mean diameter, the sauter mean diameter, the 10th, 50th and 90th percentile points, and the span values were consistent with the geometric mean diameter data. The results of this study indicate that the use of a light scattering particle size analyzer provides a quick, simple and reliable technique for evaluating the batch-to-batch variability in magnesium stearate.