Characteristic particle size

Hie US Armed Forces requirements for oxalic acid are covered by Federal Spec 0-0-690a, Oxalic Acid, Dihydrate, Technical , (July 1, 1968). It details three classes class 1—large crystals, class 2—small crystals, and class 3— powder. It requires a min assay of 99.0% by wt as H2C204.2H20, a max ash content of 0.20% by wt, and the following particle size characteristics using US Standard sieves ... 

Category Range of particle size Characteristics of system Examples... 

Figure 17-46 shows such a performance curve for the collection of coal fly ash by a pilot-plant venturi scrubber (Raben "Use of Scrubbers for Control of Emissions from Power Boilers, United States-U.S.S.R. Symposium on Control of Fine-Particulate Emissions from Industrial Sources, San Francisco, 1974). The scatter in the data reflects not merely experimental errors but actual variations in the particle-size characteristics of the dust. Because the characteristics of an industrial dust vary with time, the scrubber performance curve necessarily must represent an average material, and the scatter in the data is frequently greater than is shown in Fig. 17-46. For best definition, the curve should cover as wide a range of contacting power as possible. Obtaining the data thus requires pilot-plant equipment with the flexibility to operate over a wide range of conditions. Because scrubber performance is not greatly affected by the size of the unit, it is feasible to conduct the tests with a unit handling no more than 170 m3/h (100 ftVmin) of gas.

Bagley, S. T., Gratz, L. D., Johnson, J. H., and McDonald, J. F. 1998. Effects of an Oxidation Catalytic Converter and a Biodiesel Fuel on the Chemical, Mutagenic, and Particle Size Characteristics of Emissions from a Diesel Engine. Environ. Sci. Technol., 32,1183-1191. 

Nerbrink, O., Dahlback, M., and Hansson, H. C. (1994), Why do medical nebulizers differ in their output and particle size characteristics J. Aerosol Med., 7,259-276. 

Emulsion polymerization reactions are sometimes carried out with small seed particles formed in another reaction system. A number of advantages can he derived from using seed particles. In a batch reactor seed latex can he helpful hi controlling particle concentration, polymerization rate, particle morphology, and particle size characteristics. In a CSTR the use of a feed stream containing seed particles can also help to prevent conversion and/or surface tension oscillations, which are caused by particle formation phenomena, This factor will be discussed in more detail later in this chapter. 

Size fractionation is a very important preparatory step in mineralogical analysis and it is essential to know the particle size characteristics of material being analysed if results are to be reproducible. Preparation for most samples therefore begins with disaggregation and/or grinding. However, it must be emphasised that clay minerals can be easily damaged by mechanical treatment and it should be kept to a minimum. Samples may be mixed with a volatile inert organic liquid (e.g. isopropyl alcohol) prior to... 

Direct Emulsification. Polymer colloids called "artificial latexes" can be prepared by dispersion of bulk polymers or polymer solutions into an aqueous medium. Direct emulsification processes are reviewed by ElAasser (23). The preparation procedures involve mechanical dispersion that may be followed by removal of solvent. According to ElAasser "the efficiency of emulsification," and hence the particle size characteristics of the latex, "is determined by the efficiency of formation of fine droplets and the efficiency of stabilization of the formed droplets." Important parameters in the process include the source of energy or agitation, its intensity, and duration type and concentration of emulsifiers mode of addition of emulsifier and the two phases density ratio of the two phases temperature and the rheology of the two phases. 

Dolovich M. Measurement of particle size characteristics of metered dose inhaler (MDI) aerosols. J Aerosol Med 1991 4 251-253. 

The dominant influence of supersaturation on the particle size characteristics of a precipitate has been summed up in the so-called Weimam laws of precipitation (Weimarn, 1926) which, whilst open to criticism from a theoretical point of view, still give useful guidelines for batch precipitation behaviour. The laws cannot be expressed concisely, but Figure 8.4 assists in their interpretation ... 

The nickel-iron battery cell fabrication process is essentially unchanged in over 50 years. Special attention must be paid to use high purity materials and particle size characteristics of the active materials. The iron negative active material is made from pure iron that is dissolved in sulfuric acid. The resulting Fe(S04>2 is recrystallized and dried. This is washed free of sulfuric acid and roasted at 915°C to form a mixture of FeaOs and Fe metal and is, then, blended with small amotmts of FeS, sulfur, and HgO for use in the negative plate assembly. 

The effect on the gold particle size characteristics of calcination in air could be followed with a combination of UV-visible diffuse reflectance spectroscopy, monitoring the evolution of the surface plasmon absorbance, and TEM. The well established Kubelka-Munk relation for the diffuse reflectance of non-translucent films of fine powders gives the following for each wavelength ... 

This technique of diffuse reflectance provides a quick and qualitative check of the particle size characteristics of catalysts containing gold (or other group IB metals) on white support powders, and can be used as a complement to TEM observations. The advantages are that it can be used on systems too dilute or... 

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