ASTM-C721:2020 Edition

1.1 These test methods cover the estimation of the average particle size in micrometres of alumina and silica powders using an air permeability method. The test methods are intended to apply to the testing of alumina and silica powders in the particle size range from 0.2 to 75 μm.

1.2 The values stated in SI units are to be regarded as standard, with the exception of the values for density and the mass used to determine density, for which the use of the gram per cubic centimetre (g/cm³) and gram (g) units is the long-standing industry practice; and the units for pressure, cm H₂O—also long-standing practice.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.