Sieve calibration

The particle size distribution of AP was determined and Compared using the Ro-Tap, the Alpine Air Jet Sieve and the Micromerograph. For this purpose six different samples of ground AP were chosen and separated using sieves calibrated with National Bureau of Standards spherical glass beads. The results were plotted... 

Sieve analysis, based on either vibratory or suction principle, uses a series of standard sieves calibrated by the National Bureau of Standards. The method is generally used for screening coarse particles down to a material as fine as 44 pm (No. 325 sieve). Sieves produced by photoetching and electroforming techniques are now available with apertures from 90 down to 5 pm. 

To evaluate the effect of shape factors of particles, the electro-formed sieves were calibrated microscopically with two different materials ... 

Permeability is another method for obtaining information about pcirticle diameters. If one packs a tube with a weight of powder exactly equal to its density, and applies a calibrated gas pressure through the tube, the pressure drop can be equated to an average particle size. The instrument based on this principle is called the "Fisher Sub-Sieve Sizer ". Only one value can be obtained but the method is fast and reproducible. The instrument itself is not expensive and the method can be applied to quality control problems of powders. Permeametry is usefiil in the particle range of 0.5 to 50 n. 

Low-temperature adsorption is also useful for the quantitative transfer of gases into special apparatus. For example, a small quantity of activated molecular sieve in a freeze-out tip on an infrared cell may be used for the identification of methane or, when placed in a freeze-out tip on a manometer and calibrated volume, the molecular sieves permit the measurement of the quantity of noncon-densable gas. 

Monodispersed polystyrene sols are used as calibration standards for electron microscopes, light scattering photometers, Coulter counters, particle sieves, etc. Monodispersed silica is used for antireflection lens coatings. Monodispersity (even at a modest level) can usefully be exploited in photographic film, magnetic devices, pharmaceutical preparations and catalysis. 

The above equations apply only when the weight-in-size distribution is known to follow the log-probability distribution. Their application to a complete sieve-analysis also depends upon calibration of each sieve of the series used as explained in subsequent paragraphs,... 

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