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![]() Sieves for Pharmacopeial Testing Sieves for Pharmacopeial testing are described under Particle Size Distribution Estimation by Analytical Sieving ![]() ![]() ![]()
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![]() Powdered Vegetable and Animal Drugs In determining the powder fineness of a vegetable or animal drug, no portion of the drug may be rejected during milling or sifting unless specifically permitted in the individual monograph. ![]()
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![]() Air Permeation Method for Determining Fineness of Sub-sieve Size Particles The average particle size measured is in the range of 0.2 to 50 µm. The test specimen is loaded into a precision bore tube and is compacted between two paper disks and porous plugs by a rack-and-pinion packing plunger. The determination of the particle size of the specimen in the uniformly packed column is based on its resistance to the flow of a closely regulated current of dried air. The liquid level of a flowmetermanometer corresponds directly to particle size. Special handling instructions and procedures are provided in the individual monographs. ![]()
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Classification of Powder Fineness ![]() x90 = particle dimension corresponding to 90% of the cumulative undersize distribution x50 = median particle dimension (i.e., 50% of the particles are smaller and 50% of the particles are larger) x10 = particle dimension corresponding to 10% of the cumulative undersize distribution The following parameters may be defined based on the cumulative distribution. QR(x) = cumulative distribution of particles with a dimension less than or equal to x where the subscript R reflects the distribution type.
Therefore, by definition:
QR(x) = 0.90 when x = x90 QR(x) = 0.50 when x = x50 QR(x) = 0.10 when x = x10 ![]() An alternative but less informative method of classifying powder fineness is by use of the terms in the following table.
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Classification of Powders by Fineness
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Auxiliary Information
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USP35NF30 Page 390
Pharmacopeial Forum: Volume No. 28(2) Page 611
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