Particle size analysis using sedimentation

Pye, K. and Blott, S. J. (2004b). Particle size analysis of sediments, soils and related particulate materials for forensic purposes using laser granulometry. Forensic Sci. Int. 144, 19-27. 

Kohn Pipette. Apparatus for particle-size analysis by sedimentation it has been used more particularly in the study of clay soils. (M. Kohn, Z. Pflanz. Dung., All, 50,1928.)... 

Given tire a size dependence of tire settling rate, sedimentation can be used for particle size analysis. Indeed, a quick... 

Turbidimetric methods for particle size analysis (Refs 10, 16 27) are used in conjunction with sedimentation procedures to determine the concn of particles at given distances below the surface at successive time intervals. From these data, and Stokes law, particle size distribution can be calculated... 

A complete particle-size analysis can require the use of various analysis technologies. A microscopic examination may be performed before the sieve analysis, which in turn can be followed by a sedimentation analysis or the recording and the evaluation of a diffraction pattern. 

It is our objective in this chapter to outline the basic concepts that are behind sedimentation and diffusion. As we see in this chapter, gravitational and centrifugal sedimentation are frequently used for particle-size analysis as well as for obtaining measures of solvation and shapes of particles. Diffusion plays a much more prevalent role in numerous aspects of colloid science and is also used in particle-size analysis, as we see in Chapter 5 when we discuss dynamic light scattering. The equilibrium between centrifugation and diffusion is particularly important in analytical and preparative ultracentrifuges. 

Brown and Skrebowski [37] first suggested the use of x-rays for particle size analysis and this resulted in the ICl x-ray sedimentometer [38,39]. In this instrument, a system is used in which the difference in intensity of an x-ray beam that has passed through the suspension in one half of a twin sedimentation tank, and the intensity of a reference beam which has passed through an equal thickness of clear liquid in the other half, produces an inbalance in the current produced in a differential ionization chamber. This eliminates errors due to the instability of the total output of the source, but assumes a good stability in the beam direction. Since this is not the case, the instrument suffers from zero drift that affects the results. The 18 keV radiation is produced by a water-cooled x-ray tube and monitored by the ionization chamber. This chamber measures the difference in x-ray intensity in the form of an electric current that is amplified and displayed on a pen recorder. The intensity is taken as directly proportional to the powder concentration in the beam. The sedimentation curve is converted to a cumulative percentage frequency using this proportionality and Stokes equation. 

I NF 11-683 Test Methods for Particle Size-Analysis-Particle Size by Variable Height Gravity Sedimentation in a Liquid-Method Using X-ray Adsorption Measurements, 360... 

During particle size analysis, in addition to screening, sifting, and counting, sedimentation techniques are often used which produce unequivocal results only if the individual particles can move without influencing each other. For that reason, very dilute suspensions are used. Nevertheless, it is possible that agglomerates form or already... 

For particle-size analysis, the fine earth was treated with 3 M HjOj and sonicated (15 min, 15 kHz) coarse, medium and fine sand were retrieved by sieving at 0.25, 0.10 and 0.05 mm, respectively silt was separated from clay by sedimentation after dispersion in 0.01 M NaOH. The pHjj g was measured potentio-metrically (solid/liquid ratio of 1 2.5). Organic C and total N were measured on acidified samples using a Carlo Erba NA1500 analyser. Available P was determined according to Olsen et al. (1954). Effective cation exchange capacity (ECEC) was determined by summation of the cations displaced with 0.2 M BaCl2 and analyzed by atomic absorption with a Perkin-Elmer llOOB spectrophotometer. 

A dilution of the milling solvent(s) would have to be used in any sedimentation tests, since the slurries should never be dried before testing, and a dilute solution is required for most of the tests. When the particle size analyses duplicate one another after milling for two different periods of time, the end point has been reached for the dispersion milling. As we mentioned previously, this time frame is rarely if ever longer than 24 hours. The d Q and particle size distribution of the dispersed powder, even after as brief a milling time as two hours, may be much different than those of the as-received powder, depending on the particle size analysis measurement s ability to... 

Harris s three-parameter equation is very flexible and can be closely fitted to most uni-modal distributions. As its mathematical form lends itself easily to further treatment it has been used in a relatively involved evaluation of results from scanning centrifugal sedimentation instruments for particle size analysis. ... 

If, for instance, the separation effect is influenced only by the mobility of particles in fluids, the terminal setding velocity or Stokes diameter could be used for the size x and the method of particle size analysis would be chosen accordingly (sedimentation or elutriation). 

The interaction of fineparticles in a suspension has been reviewed in detail in Reference 1 B. H. Kaye and C. R. G. Treasure, The Thermal Stability of Sedimenting Suspensions Used to Measure Particle She.Distx sxdxotxd, Materiak Research and Standards, 5 11 (1965). R. Davies and B. H. Kaye, The Effect of Cluster Instability in Suspensions and Particle Size Analysis Measurements with the Cahn Balance Particle Size Analysis Conference 1970, Bradford University, British Society for Analytical Chemistry, London. 

Measured size distributions depend not only on the physical dimensions of the particles but also on the method of size analysis used. Size distributions by the Coulter Principle will only agree with sedimentation data if the particles are spherical. Indeed the difference is a measure of particle shape. Since classifiers separate particles on the basis of their Stokes sizes a sedimentation method of size analysis should be used to determine their grade efficiency. Sedimentation analyses are also applicable to many other industrial situations. 

In the paper presented here I intend to describe some of the methods for sedimentation particle size analysis in current use. Although I do not intend to cover operating procedures it would be remiss of me not to mention the two factors which, more than anything else, lead to incorrect analyses. The first is incorrect sampling analyses are carried out on from a... 

The sedimentation methods of particle size analysis, both gravitational and centrifugal, have, over the years, generated many contributions and are still extensively used in many traditional industries. PSA 91 saw however only three such contributions [Allen (2) Bernhardt], one which was a Keynote lecture reviewing the historical developments of this fundamental method. The Andreasen sedimentation technique and sieving continue as essential methods used for the characterisation of many certified reference materials. 

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