1.1 This standard describes the optical microscope method for determining the particle size of powders which pass through a 75-micron IS Sieve IS: 460-1962〓 as far as the particle shape and refractive index will permit. The method of measurement is so arranged that the size analyses of the particles, in microns, are expressed in the form of a consecutive ∫2 series, namely 75, 53, 37, 27, 19, 13,9·4, 6·6, 4·7, 3·3, 2·3, 1·7, 1·2，0·8, 0·6〓.
1.2 The size distribution is expressed either by number or by volume or weight and in terms of the diameters of circles having the same projected areas as the particles. The method is normally used for particles having projected diameters in the range 0·6-75 microns but the upper size limit can be extended to measure particles up to 150 microns (see 4.3).
IS 5258-1969 history
1970IS 5258-1969 Determination of Powder Particle Size by Optical Microscopy