Other disadvantages include slowness of measurement, which makes repeat measurements tedious. Irregularly shaped particles, such as disc-shaped kaolins, take even longer to settle due to their increased drag compared with spherical particles. 50m m. Electrozone sensing This technique was originally developed for sizing blood cells. For industrial materials it has many drawbacks. It is difficult to measure emulsions and impossible to measure sprays.
Dry powders require suspension.
Measurement must take place in an electrolyte, which creates difficulties for organic materials, and the method requires calibration standards that are expensive and change size in distilled water and electrolyte. Microscopy This is an excellent technique that allows direct examination of the particles in question, and one that is relatively cheap. However, it is not suitable as a quality or production control technique beyond the level of simple judgement. Also, as relatively few a particles are examined, there is a real danger of unrepresentative sampling and if weight distribution is measured results are magnified. Missing one 10m m particle has the same effect as missing one thousand 1m m particles.