Sieving range

The sieve is made of a wire mesh cloth of standard sizes held in place by a circular metal frame. The diameter of the sieve ranges from 4 to 18 in., and the height may vary from 1 to 2 in. Three popular sieve series are used the Tyler Series, the first commercial laboratory screens the U.S. Standard Series and the U.S. Alternative Series. Both the U.S. Alternative Series and the Tyler Series designations use the approximate number of opening per linear inch. However, the U.S. Standard Series is the preferred designation and is recommended by the International Standards Organization (ISO). Table 15.3 shows the U.S. Sieve Series and Tyler Series equivalents for a selected number of screens. 

Considerable development has taken place into techniques for size separation in the sub-sieve range. As discussed by Work 27, the emphasis has been on techniques lending themselves to automatic working. Many of the methods of separation and much of the equipment has been developed for use in the mining and metallurgical industries, as described by Taggart 28). ... 

The majority of applications for fluid energy mills are for producing powders in the sub-sieve range, of the order of 20 p,m and less, and it may be noted that the power consumption per kilogram is proportionately higher than for conventional milling systems which grind to a top size of about 44 p,m. 

Processes for the separation of particles of various sizes and shapes often depend on the variation in the behaviour of the particles when they are subjected to the action of a moving fluid. Further, many of the methods for the determination of the sizes of particles in the sub-sieve ranges involve relative motion between the particles and a fluid. 

Emmett, P. H. (1941), ASTM Symposium on New Methods for Particle Size Determination in the Sub-Sieve Range, p. 95. 

Work involving the slope of the gradation curve in this sieve range has not yet been completed. 

Consider particles with an initial size distribution in the sieve range from a to aj and define an as the initial radius of a particle, which shrinks to a value a at strain e. Hence, we have... 

Molecular sieving range (molecular porosity) - porous electrodes... 

Sieves Use a set of standard sieves, ranging from 80-mesh to 325-mesh, conforming to the specifications in ASTM Designation Ell (Sieves for Testing Purposes). 

Catalyst Characterization. The three SAPO molecular sieves employed in this study represents the three pore sizes of molecular sieves, ranging tom 0.4 nm to 0.8 nm. While SAPO-5 and SAPO-11 have unidimensional pores, SAPO-34 has a multidimensional pore system with supercages. The chemical composition and total ammonia uptake of the tifiree SAPO molecular sieves are listed in Table I. 

Membranes prepared by the majority of the established methods have limitations in their pore sizes. To make membranes with finer pore diameters suitable for more demanding separation and membrane reactor applications, a widely practiced technique is to modify the pores or the surface of an existing membrane structure which has already been made. This encompasses a variety of techniques. Some of them are based on gas or vapor phase reactions. Others modifications occur in liquid phase. Some progress having pore diameters in the molecular sieving range has been made. 

Practically all the methods for determination of the particle-size distribution in the sub-sieve range utilize a fluid-dynamic system based on Stokes law (177) ... 

The same standards can be separated with poly(ethylene glycol) (PEG 200 molecular mass 200,000 g mol-1) in a 5% wlw) solution or with poly(vinylpyrrolidone) K90 (1% wlw). As can be seen in Fig. 6, the separation ranges and the broadness of the peaks are quite different, because of differences in the sieving ranges of the polymeric additives. 

For pores only slightly larger than the size of the molecules, the diffu-sivity is much less than that predicted by Eq. (4.7). For example, measured diffusion coefficients of -alkanes in zeolite crystals (molecular sieves) range from 10 to 10 cm /sec, compared to about 10 cm /sec from Eq. 

Sieve (between sieves) range (%) Sieve (between sieves) range (%)... 

M0ller N (1971) Studies on particle size problems VII. Specific particle nnmlxa as a measure in pharmacopoeial tests of particle size in the sub-sieve range. Dan Tidsskr 45 125-134... 

In the preparation of Paracetamol-codeine suppositories FNA (Table 11.5), paracetamol (45) is used as small particles because they provide a faster release rate [25]. In addition, the small particles sediment less rapidly during the preparation of the suppositories. Particles with this degree of fineness, however, establish a poor flow and have a high bulk volume. This makes them unsuitable for processing into capsules. For this purpose the paracetamol quality (90-500) is used. For sieve ranges in relation to particle size see Table 23.3. 

JP Olivier, GK Hickin, C Orr Jr. Rapid automatic particle size analysis in the sub-sieve range. Powder Technol 4 257-263, 1970/1971. 

Koresh J, Soffer A. Study of molecular sieve carbons. Part 1. Pore structure, gradual pore opening and mechanism of molecular sieving. JCS Faraday I 1980 76 2457-2471. Part 2. Estimation of cross-sectional diameters of non-spherical molecules. JCS Faraday I 1980 76 2472-2485. Molecular sieving range of pore diameters of adsorbents. JCS Faraday I 1980 76 2567-2569. 

---