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SIZE ANALYSIS OF MINUS 44 MICRON DUST PARTICLES,
NAVAL RADIOLOGICAL DEFENSE LAB SAN FRANCISCO CALIF
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A method of particle size analysis utilizing ultrasonic energy and Micro Mesh sieves has been developed for dust particles with diameters less than 44 microns. The particle size distributions of volcanic dust and dust from ground surface explosions were determined. The new method yields discrete particle size fractions, rather than fractions that contain all particle sizes less than a stated size, as produced by liquid sedimentation methods. Particulate samples were wet sieved through a 44-micron Tyler sieve onto a 40-micron Micro Mesh sieve. The surface of the screen and the particles were immersed in water in an ultrasonorator tank for a few minutes. Particles with diameters less than 40 microns passed through and were collected and transferred to a 30 micron screen. The process was repeated for 30-, 20-, and 10-micron Micro Mesh sieves. Each sieve and the material retained by it were dried in an oven at 110C. The dried particles were recovered, weighed, and later used for photomicrographic studies, density measurements, etc. Author
APPROVED FOR PUBLIC RELEASE