Median particle size

The term essentially a drag coefficient for the dust cake particles, should be a function of the median particle size and particle size distribution, the particle shape, and the packing density. Experimental data are the only reflable source for predicting cake resistance to flow. Bag filters are often selected for some desired maximum pressure drop (500—1750 Pa = 3.75-13 mm Hg) and the cleaning interval is then set to limit pressure drop to a chosen maximum value. 

Chemica.1 Properties. The reactivity of magnesium hydroxide is measured primarily by specific surface area in units of /g and median particle size in p.m. Reactivity ranges from low, 1-2 /g, 5 p.m, eg, Kyowa s product to high, 60-80 /g, 5—25 pm, eg, Barcroft s CPS and CPS-UF... 

Specialty Aluminas. Process control (qv) teclmiques permit production of calcined specialty aluminas ha nng controlled median particle sizes differentiated by about 0.5 ]lm. Tliis broad selection enables closer shrinkage control of high tech ceramic parts. Production of pure 99.99% -AI2O2 powder from alkoxide precursors (see Alkoxides, metal), apparently in spherical form, offers the potential of satisfying the most advanced appUcations for calcined aluminas requiring tolerances of 0.1% shrinkage. 

Kaolin type Brightness, % Maximum soHds, % Median particle size, p.m Uses Relative cost... 

Each of the PLgel individual pore sizes is produced hy suspension polymerization, which yields a fairly diverse range of particle sizes. For optimum performance in a chromatographic column the particle size distribution of the beads should be narrow this is achieved by air classification after the cross-linked beads have been washed and dried thoroughly. Similarly, for consistent column performance, the particle size distribution is critical and is another quality control aspect where both the median particle size and the width of the distribution are specified. The efficiency of the packed column is extremely sensitive to the median particle size, as predicted by the van Deemter equation (4), whereas the width of the particle size distribution can affect column operating pressure and packed bed stability. 

Material Median particle size, pm Minimum explosive concentration g/m= p max bar ga (dp/dt)max> ba r/sec Ksi bar-m sec Dust Hazard Class... 

Material Median particle size, Mm Minimum explosive concentration g/m3 P oux bar ga (dP/dl)max, bar/sec KSt Dust bar-m Hazard sec Class ... 

Particle size is the rate-controlling factor in the case of cements formed using IP zinc oxide (Smith, 1958 Norman e/a/., 1964). Setting time appears to be proportional to the median particle size (Prosser Wilson, 1982). By contrast, the setting times of cements prepared from TD zinc oxide do not appear to relate to particle size. 

The palladium-tin catalysts were prepared by Engelhard on a commercial wood based carbon powder with a BET snrface area of approximately 800 m /g and a median particle size (D50) of 19 microns. The preferred carbon was chosen mainly for having good filtration properties. Catalysts with essentially equivalent activities for selectivity and conversion could also be made on two other similar carbons. The preparation process is proprietary but is based on the well-known adsorption-deposition technique (8). Reduction during the preparation process was accomplished via an Engelhard proprietary method. A series of catalysts containing from 1 to 7.5 wt% palladium and from 0 to 1 wt% tin were prepared by the same technique and provided for the experimental program. 

Dust Median particle size (Mm) Minimum explosive dust concentration (9/m3) Pmax (bar g) st (bar-m/s) Minimum ignition energy (mJ)... 

Dust Median particle size, im Minimum explosive dust cone., g/m3 Pm3x, barg KSl, bar-m/s Minimum ignition energy, mj... 

Figure 19 Mean plasma concentrations following the administration of felodipine suspension to Labradors. Median particle size 125 pm in = 6) dose 10 mg, in either 0.9% saline (NS) or 5% glucose (Glc.) solution. Source From Ref. 30.

In addihon to shape selechvity and acid-site strength, other catalyst characteristics that influence the catalyhc performance of SAPO-34 have also been idenhfied. Variahon in the SAPO-34 gel composition and synthesis condihons have been were used to prepare samples with different median particle sizes and Si contents (Tables 15.3 and 15.4) [104]. In these samples the median parhcle size was varied from 1.4 to 0.6 xm, and the Si mole frachon in the product was varied from 0.14 down to 0.016. A comparison of samples B and E (which have similar parhcle size distributions) shows that reducing Si content decreases propane formation and increases catalyst life. A comparison of samples B and C (which have similar Si contents) illushates an increase in catalyst life with a reduchon in parhcle size. 

A.J.O Neil, R. Jee and A.C. Moffat, The application of mnltiple linear regression to the measnrement of the median particle size of drugs and pharmacentical excipients by near-infrared spectroscopy. Analyst, 123, 2297-2302 (1998). 

Frake et al. compared various chemometric approaches to the determination of the median particle size in lactose monohydrate with calibration models constrncted by MLR, PLS, PCR or ANNs. Overall, the ensuing models allowed mean particle sizes over the range 20-110/tm to be determined with an error less than 5 pm, which is comparable to that of the laser light diffraction method nsed as reference. Predictive ability was similar for models based on absorbance and second-derivative spectra this confirms that spectral treatments do not suppress the scattering component arising from differences in particle size. 

P. Frake, I. Gill, C.N. Luscombe, D.R. Rudd, J. Waterhouse and U.A. Jayasooriya, Near-infrared mass median particle size determination of lactose monohydrate, evaluating several chemometric approaches. Analyst, 123, 2043-2046 (1998). 

Based on phase-equilibrium data in the Master diagram (Figure 9.8-12) (where S-l and 1-V equilibrium data are presented) the experiments for cocoa butter micronization using the PGSS process were carried out. The pre-expansion pressure was in the range of 60 to 200 bar and at temperatures from 20 to 80°C. The micronization with the nozzle D = 0.25 mm resulted in fine solid particles with median particle sizes of about 62 pm. In Figure 9.8-13 the morphology of a cocoa-butter particle is presented. 

Changes in the solid state can inLuence dissolution rate through the surface area term or th< solubility term. Surface area differences can arise from simple particle-size effects between different crystal forms and also from shape factors. Different crystal habits and shapes can alter the exposei surface area without a change in median particle-size measurements, since these are often calculati... 

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