![]() ![]() Test procedures for sieving powder materials are described under Particle Size Distribution Estimation by Analytical Sieving
![]() ![]() Sieves for Pharmacopeial Testing— Sieves for Pharmacopeial testing are described under Particle Size Distribution Estimation by Analytical Sieving ![]() ![]() 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. 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 flowmeter-manometer corresponds directly to particle size. Special handling instructions and procedures are provided in the individual monographs. Classification of Powder Fineness— Powder fineness may be classified by determining the smallest sieve opening through which a specified quantity of material passes. Results are typically reported as the following: d90 = smallest sieve opening through which 90% or more of the material passes d50 = smallest sieve opening through which 50% or more of the material passes d10 = smallest sieve opening through which 10% or more of the material passes. An alternative but less informative method of classifying powder fineness is by use of the terms in the following table.
Classification of Powders by Fineness
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USP32–NF27 Page 357
Pharmacopeial Forum: Volume No. 28(2) Page 611
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