Size distribution by sedimentation

JIS Z8820 General Rules for the Determination of Particle Size distribution by Sedimentation in Liquid, 360... 

The response of a brick-clay to deflocculants is of little technological interest, since such clays are not cast deflocculants are used, however, in determining the size distribution by sedimentation methods, and it is of interest that, for the Etruria Marls, a mixture of 5 parts by weight of Calgon to 1 part of NaOH was a more effective deflocculant than sodium oxalate. All the other clays mentioned were deflocculated well with this mixture. This behaviour is probably related to the exchangeable ions of the clays. 

Schure, M.R. Barman, B.N. Giddings, J.C. Deconvolution of nonequilibrium band broadening effects for accurate particle size distributions by sedimentation field-flow fractionation. Anal. Chem. 1989, 61, 2735. 

The particle size deterrnined by sedimentation techniques is an equivalent spherical diameter, also known as the equivalent settling diameter, defined as the diameter of a sphere of the same density as the irregularly shaped particle that exhibits an identical free-fall velocity. Thus it is an appropriate diameter upon which to base particle behavior in other fluid-flow situations. Variations in the particle size distribution can occur for nonspherical particles (43,44). The upper size limit for sedimentation methods is estabHshed by the value of the particle Reynolds number, given by equation 11 ... 

Fig. 4. Aggregate size distributions by electron microscope image analysis (D and centrifugal (Z9 sedimentations for N220 and N351 carbon blacks (8).

A dispersion of the sample is placed on top of a liq of greater density. The rate of sedimentation is detd by measuring the sediment vol at fixed time intervals. The results are converted to a size distribution by Stoke s Law Nitrogen Adsorption. The amt of N adsorbed on a sample is detd by carefully measuring the press change of a known vol of N exposed to a known wt of dry mat at constant temp. The info is used to detn the surface area which is converted to a particle size distribution Turbidometric Methods. The absorption of a beam of light passing thru a suspended sample in a suitable liq is measured as a function of time. 

Giddings JC, Myers MN, Moon MH, Barman BN (1991) Particle separation and size characterization by sedimentation field-flow fractionation. In Provder T (ed) Particle size distribution. American Chemical Society, Washington, DC, pp 198-216... 

ISO/WD 13317-1 Determination of Particle Size Distribution by Gravitational Liquid Sedimentation Methods- Part I (1996) General Principles and Guidelines, 360... 

Other samples of alkaline slurry were subjected to particle size analysis by sedimentation. With the —43 xm + 1.2 [im fraction this analysis was done in a 50-mm-diameter settling column of dilute slurry with a tared pan at the base to record continuously the mass of sedimented solid. The data were analyzed by the method of Oden (8), and the particle size distribution (Stokesian diameter), expressed on a mass percent basis, was calculated. 

Brown, C. Particle Size Distribution by Centrifugal Sedimentation, /. Phys. Chem, 1944, 48, 246. 

Determination of particle size distribution by gravitational sedimentation in a liquid and attenuation measurement Pore size distribution and porosity of solid materials - Evaluation by mercury porosimetry and gas adsorption International Union of Pure and Applied Chemistry, Bank,... 

All of the gravity sedimentation techniques, with the exception of photo-sedimentometers which detect the projected area of the particles (which in turn is proportional to particle surface) measure size distribution by mass. Photosedimentometers can only give useful results for particles coarser than around 5 pm because for finer particles the wavelength of light becomes comparable to the particle size, the laws of geometric optics break down and the so-called light extinction coefficient becomes highly size dependent. 

S. Berg, Determination of Particle Size Distribution by Examining Gravitational and Centrifugal Sedimentation according to the Pipette Method and with Divers, ASTM, Special Technical Publication No. 234, 1958, pp. 143-171. 

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. 

Berg, S. Determination of particle size distribution by examining gravitational and centrifugal sedimentation to the pipett method and with divers. Symp. PSA, June 1958, Boston, ASTM STP 234 (1959), p. 143 - 171 /4/ Chung, H. S. Hogg, R. The effect of Brownian motion on particle size analysis by sedimentation. Powder Techn. 41 (1985) 3, p. 211 - 216 /5/ Allen, T. Sedimentation techniques of particle size measurement. Conf. PSA Sept. 1985, Bradford, Proceed, p. 24 - 45... 

In particle-size measurement, gravity sedimentation at low soHds concentrations (<0.5% by vol) is used to determine particle-size distributions of equivalent Stokes diameters ia the range from 2 to 80 pm. Particle size is deduced from the height and time of fall usiag Stokes law, whereas the corresponding fractions are measured gravimetrically, by light, or by x-rays. Some commercial instmments measure particles coarser than 80 pm by sedimentation when Stokes law cannot be appHed. 

Particle Size Distribution. Almost every feed slurry is a mixture of fine and coarse particles. Performance depends on the frequency of distribution of particle size ia the feed. Figure 5 shows that whereas all of the coarse particles having a diameter greater than some are separated, fewer of the very fine particles are, at any given feed rate. The size distribution frequency of particles ia feed and centrate for a fine and coarse feed are quite different. More coarse particles separate out than fine ones. Classification of soHds by size is often done by centrifugal sedimentation. 

Aerosol Dynamics. Inclusion of a description of aerosol dynamics within air quaUty models is of primary importance because of the health effects associated with fine particles in the atmosphere, visibiUty deterioration, and the acid deposition problem. Aerosol dynamics differ markedly from gaseous pollutant dynamics in that particles come in a continuous distribution of sizes and can coagulate, evaporate, grow in size by condensation, be formed by nucleation, or be deposited by sedimentation. Furthermore, the species mass concentration alone does not fliUy characterize the aerosol. The particle size distribution, which changes as a function of time, and size-dependent composition determine the fate of particulate air pollutants and their... 

---