The instrument used is a Micromeritics Sedigraph 5100.
For dry powders a representative 10-20g subsample is taken and dispersed in approximately 75mL of 1000ppm sodium hexametaphosphate (Calgon) using a Cole-Palmer 8851 (or equivalent) ultrasonic bath for 15 minutes. Some powders may require the addition of a wetting agent to enable full dispersion. In this instance, Alcopol “O” is used.
For slurry samples a representative subsample is taken and dispersed in 1000ppm sodium hexametaphosphate (using the same bath) for 10 minutes.
The resulting slurry is then homogenised before being dispensed into the sample loading chamber. The sample concentration may have to be adjusted to give an appropriate full scale X-ray attenuation line once the sample is loaded into the instrument. The density, used in the Micromeritics software to calculate the size distribution of the material, is set at an appropriate value for the supplied sample. The sample is run in the sedimentation system for a time dependant on the size distribution range requested.
Any material greater than 106 µm in size has to be manually screened out of the sample, dried, weighed and the percentage calculated and entered into the report size range.
