Journal of Research of the National Bureau of Standards, volume 90, number 1, January - February 1985

The average diameter of the first micrometer particle size standard, an aqueous suspension of monosized polystyrene spheres with a nominal 1 micron diameter, was determined by three independent techniques. In one technique the intensity of light scattered by a diluted suspension of polystyrene spheres was measured as a function of scattering angle, using He-Ne laser polarized in the vertical direction. The second technique consisted of measuring as a function of angle the intensity of light scattering from individual polystyrene spheres suspended in air, using a He-Cd laser with light polarized parallel and perpendicular to the scattering plane. The measurement of row length by optical microscopy for polystyrene spheres arranged in closed-packed, two-dimensional hexagonal arrays was the basis of the third technique. The measurement errors for each technique were quantitatively assessed. Transmission electron microscopy, low through electrical sensing zone counter measurements, and optical microscopy were used to obtain detailed information on the size distribution including the standard deviation, fraction of off-size particles, and the fraction of agglomerated doubles.