Narrow size range

Pressure (P) psia Volume intruded (V) cm3 g-1 Pore radius (r) xm Mean pressure psia Mean radius (f) pm Specific surface (S) m2 g-1 AS At m2 g-1 lim-1 Ar cm3 g-1 lun-i 

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Solid samples are separated by particle size using one or more sieves. By selecting several sieves of different mesh size, particulates with a narrow size range can be isolated from the solid matrix. Sieves are available in a variety of mesh sizes, ranging from approximately 25 mm to 40 )j,m. 

To examine sedimentation in greater detail, let us examine the events occurring in a small-scale experiment conducted batchwise, as illustrated in Figure 9. Particles in a narrow size range will settle with about the same velocity. When this occurs, a demarcation line is observed between the supernatant clear liquid (zone A) and... 

For example, Dixon (1979,1981) based most of his suggestions and observations on plastic powders and granules (i.e., relatively smooth particles with narrow size ranges). 

By active surface area we meant the kinetically active part of the total surface area. According to Helgeson et al. (1984), this area is restricted to etch pits. Alternative estimates of surface areas may be obtained from measurements of specific surface area s whenever solid particles have a narrow size range. The specific surface area for spherical particles is given by... 

The authors explain their results in terms of gas-filled pits on the metal surfaces. It is argued that a fine polish results in pits of a narrow size range. The sizes are presumed to be such that a rather high superheat is required to get nucleation. The coarse finishes are presumed to give a wide range of pit sizes. Some pits will have the correct size to permit nucleation at a low superheat. 

Figure 3. Computed and measured ultrafme aerosol abundances at a remote land site. The aerosols indicated are just those that lie within the narrow size range between 2.7 11111 < dp < 4 nm. From [33]...

PLGA microspheres can be prepared in rather narrow size ranges from 0.2 /mi up to > 100 /mi. The preparation, properties and degradation of these polymers have been discussed extensively in Chapter 4 (see Section 4.5.1). PLGA microspheres can now be prepared with surface oriented PEG-chains which improves in vivo circulation time ( stealth-effects ). 

This type of distribution occurs when the measured value of the size is determined by a lai e ntunber of small additive effects, each of which may or may not operate. This distribution gives the well-known bellshaped curve shown in Figure 2.9. It might be expected that many distributions follow this function but only narrow size ranges of classified material follow this distribution. Real distributions are skewed to larger sizes. 

Efficient separations, but requires 31 hydraulic water/t solids feed. Used to produce exceptionally clean underflow fractioned into narrow size ranges. 

The standard deviation and geometric standard deviation are statistical measures of spread. The former is more commonly used with powders having a narrow size range and is the difference between the 50% and the (50 I6)% sizes. The latter is more commonly used with powders having a wide size range and is the ratio of the 50% and the non-fractional (50 16)%sizes. The standard deviation is defined as ... 

Ocular graticules having a linear scale are satisfactory for the measurement of linear dimensions of particles. Particle sizes obtained with a linear eyepiece graticule are best classified arithmetically hence it is most suited to particles having a narrow size range. 

Sieves may also be calibrated by a counting and weighing technique applied to the fraction of particles passing the sieve immediately prior to the end of an analysis. These will have a very narrow size range and the average particle size may be taken as the cut size of the sieve. A minimum number ( ) of particles need to be weighed to obtain accurate volume diameters let this weight be m and the particle density be / then ... 

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