Coulter Counter, particle sizing

J.G. Day D.R. Dillehay, ibid, 277-285 3.0) D.E. Middlebrooks, S.M. Kaye, D.J. Edel-man G. Weingarten, Preliminary Evaluation of the Coulter Counter Particle Size Instrument , PATM 1054(1963) 31) J.A. Freitag, Four-... 

Light scattering coulter counter Particle size distribution, volume average particle diameter, number average particle diameter Stability of packed bed, hydrodynamic column properties, column performance... 

The Coulter-counter particle size analyzer (larger than 0.5 pm) is used for measuring volumes of individual particles. Particles are suspended in a conductive fluid, into which electrodes are placed. As a particle passes through an aperture between the electrodes, it displaces its own volume of electrolyte, and there is a measurable change in the electrical resistance of the system. The change becomes a precise measure of particle volume. These volumes can then be put into size bins and the PSD can be constructed. 

E. J. Wynn, M. J. Hounslow, Coincidence Correction for Electrical-Zone (Coulter Counter) Particle Size Analyzers , Powder TechnoL, 93 (1997) 163—175 Information on the Coulter Counter is available from Coulter Particle Characterization Electronics Inc., R O. Box 169015, M/C 195-10, Miami, Florida, USA, 33116-9015. Information on Celloscope and Electrozone resistazone counters can be obtained from Particle Data, Inc., P. O. Box 265. Elmhurst, Illinois 60126. 

Comparison of microscopic particle size distribution with the average distribution of four identical runs made with the Coulter Counter... 

H.L. Stalcup (Ref 28) evaluated the instru- -ment for the particle size determination of HMX used in rocket formulations. He found that Coulter Counter distribution was similar to that obtained with the Micromerograph except at the large particle end, where the Micromerograph indicated particles over lOOp compared to 32 p for the Coulter Counter. Median values were 13.5p by Micromerograph and 16 p for the Coulter Counter. The samples for the Coulter Counter were run on an as received basis, ie, while still water-isopropanol wet ... 

Perhaps the most useful method for determining particle distributions is that of electrical conductivity, the most widely used instrument is the Coulter Counter (named after the Inventors), although there are now other similar instruments on the market. Originally, this instrument was designed to measure blood corpuscles which are 2-8 p in size. It has proven to be very... 

Various techniques and equipment are available for the measurement of particle size, shape, and volume. These include for microscopy, sieve analysis, sedimentation methods, photon correlation spectroscopy, and the Coulter counter or other electrical sensing devices. The specific surface area of original drug powders can also be assessed using gas adsorption or gas permeability techniques. It should be noted that most particle size measurements are not truly direct. Because the type of equipment used yields different equivalent spherical diameter, which are based on totally different principles, the particle size obtained from one method may or may not be compared with those obtained from other methods. 

For a given bulk solid, determine particle size distribution, median particle diameter dv50 (e.g., using a Coulter Counter or a Malvern Laser Diffraction Analyser) and ps. 

By using orifices of various diameters, different particle size ranges may be examined and the resulting data may then be combined to provide size distributions extending over a large proportion of the sub-millimetre size range. The prior removal from the suspension of particles of sizes upwards of about 60 per cent of the orifice diameter helps to prevent problems associated with blocking of the orifice. The Coulter Counter and the Elzone Analyser work on this principle. 

Mineral standards were hand crushed to -1/4 inch, then ground to a fine powder in a ball mill (alumina elements) or Bleuler Model 526/LFS678 puck mill. The resultant powder was aerodynamically classified in a Bahco Model 6000 micro particle classifier and the finest fraction ( 18 throttle) was collected. A size criterion of 90% or more by weight of particles 5 micron and smaller in diameter was used for the mineral standards. Sizes were verified by Coulter Counter. Duplicate 13 mm KBr pellets were prepared and the spectra were weight-scaled by techniques similar to those reported by Painter (3) and Elliot (4). With one exception, all the mineral standard spectra were averages of spectra from duplicate pellets. The one exception was the iron sulfate spectrum, which was obtained as the difference spectrum by subtracting the spectrum of HCl-washed weathered pyrite from that of the weathered pyrite. A weight correction was applied to the difference spectrum. 

Literature has revealed limited kinetic data on secondary nucleation of alumina trihydrate in the precipitator of the Bayer Process for alumina production. A batch agitated, isothermal, three litre crystallizer was used in the study. A Coulter-Counter was utilized as the particle sizing equipment. The effects of seed density, supersaturation and temperature on secondary nucleation were investigated. Maximum nucleation rates were found to occur at about 70 C and for any crystallization temperature, the nucleation rate passed through a maximum. The correlated equation for the effective secondary nucleation rate of alumina trihydrate is... 

The sample collected from the crystaUizer was diluted with filtered electrolyte (2.0 wt% aqueous NaCl) and decanted to separate the fines from the coarse crystals. The dilution and decantation were repeated 5-7 times till 200 ml of the decanted sample was obtained. Preliminary tests by hoh (8) have shown tiiat these repeated decantantions were sufficient to recover at least 95% of the fines present in the original sample. Both the fine and coarse fractions were then analysed with the Coulter Counter using a 50 p.m orifice tube for the former and a 280 im orifice tube for the latter. By adjusting the Coulter Counter s settings, a set of particle number counts at different sizes (successive sizes differing by a factor of 21/3) was made for each of the 2 orifice tubes used. 

This may be due to the fact that the total number of particles is based on 1.2 pm and not 0 pm. The start of nucleation resulted in a large number of nuclei being formed but they were smaller than 1.2 pm. These nuclei were not detected by die current measurement technique. As time proceeded, these nuclei grew in size and more and more of them became detectable by the Coulter Counter used. 

Coulter counter Miused. One leading manufacturer of microparticulate silicas prefers to ciMracterize the size distribution by the three ogives dit%, and dtt% W ch denote those particle diameters that represent the upper bound for 10,50, and 90% of tte total population, respectively. For instance, a powd having nominally 10 ftm particle size may be characterized by the ogives for the three percentiles as = 5.5 fim, dn%... 

Coulter counter This is the most common type where one simply counts the number of particles or drops passing through a well-defined hole. A signal is produced, which corresponds to the size of the particle. 

Other Measurements. Particle size distributions were measured by the Coulter Counter method. Absolute density measurements were made using the well known pycnometer method. 

Fig. 4.2.9 Histograms of the size distributions of the particles shown in Fig. 4.2.8. Original and final size distributions are shown by broken and solid lines, respectively. The diameter of an equivalent sphere having the same volume as a nonspherical particle was obtained with a Coulter counter. (From Ref. 9.)...

A Coulter counter (model II) attached to an Apple computer (He) was used for all particle size measurements. 

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