Diameter particle

Some studies (6) have been carried out to measure distribution of soHds in mixing tanks. Local soHds concentrations at various heights are measured at different impeller speeds. Typical data (Fig. 16) demonstrate that very high mixer speeds are needed to raise the soHds to high levels. At low levels, soHds concentration can exceed the average concentration at low mixer speeds. These soHds distributions depend on the impeller diameter, particle size, and physical properties. 

Extra-Fine Precipitated Hydroxide. Very fine (< 1 /im-diameter) particle size hydroxide is produced by precipitation under carefully controlled conditions using specially prepared hydroxide seed. Precipitation is usually carried out at low (30 —40°C) temperatures causing massive nucleation of fine, uniform hydroxide particles (Fig. 5). Tray or tumiel Ape dry ers are used to dry the thorouglily washed filter cake to a granular product wliich is easily pulverized to obtain the fine hydroxide. Alternatively, the washed product is spray dried. Precipitation from an organic-free aluniinate Hquor, such as that obtained from the soda—sinter process, fields a very wliite product. Tlie fine precipitated hydroxide is used by the paper and plastic industries as fillers. 

Drag reduction has been reported for low loadings of small diameter particles (<60 [Lm diameter), ascribed to damping of turbulence near the wall (Rossettia and Pfefl er, AIChE J., 18, 31-39 [1972]). 

Hays measured the current associated with electrically charged 99 p.m diameter particles of styrene divinylbenzene particles as these particles traversed gaps of 520 and 137 p.m separating two parallel electrodes. Based on these results. Hays [81 ] argued for the existence of locally charged patches on the particles. 

Test bench methods for machines not too large for test cabins have been developed in order to obtain comparative results. In the case of particles, the tracer gas describes well the behavior of aerodynamic diameter particles less than 5 to 10 gm. For larger particles, correction factors should be used to modify the efficiency results obtained using the tracer gas technique. 

The theoretical minimum diameter particle to be separated in a cyclone of the basic type given by Figure 4-41 is given by the relation of Rosin [13]. 

Some authors have suggested the use of fluorene polymers for this kind of chromatography. Fluorinated polymers have attracted attention due to their unique adsorption properties. Polytetrafluoroethylene (PTFE) is antiadhesive, thus adsorption of hydrophobic as well as hydrophilic molecules is low. Such adsorbents possess extremely low adsorption activity and nonspecific sorption towards many compounds [109 111]. Fluorene polymers as sorbents were first suggested by Hjerten [112] in 1978 and were tested by desalting and concentration of tRN A [113]. Recently Williams et al. [114] presented a new fluorocarbon sorbent (Poly F Column, Du Pont, USA) for reversed-phase HPLC of peptides and proteins. The sorbent has 20 pm in diameter particles (pore size 30 nm, specific surface area 5 m2/g) and withstands pressure of eluent up to 135 bar. There is no limitation of pH range, however, low specific area and capacity (1.1 mg tRNA/g) and relatively low limits of working pressure do not allow the use of this sorbent for preparative chromatography. 

In the second view of the three-dimensional crystals the projected image normal to the plane of the lamellae (Fig. 7) shows ordered arrays of 40-50-A-diameter particles, that represent the cytoplasmic domains of ATPase molecules [156]. The crystals... 

The 1000 A column did not show any resolution between 312 nm and 57 nm particle sizes. Shown in Fig.2 are the calibration curves for the 2000 A and 3000 A columns and for their combination. The 57 nm particle standard appears to have been erroneously characterized by the supplier. This was subsequently confirmed by electron microscopy. The 2000 X column exhibited a sharp upturn in its calibration curve close to the exclusion limit. It is to be noted that while data points corresponding to 312 and 275 nm diameter particles appear on individual column calibration curves, they are not indicated for the calibration curve of the combination. This is because these larger diameter particles were completely retained in the packed colimms, generating no detector response. The percentage recovery for these particles from individual columns was considerably less than 100 resulting in their complete retention when the columns were combined in series. 

The data shown in Figures 6 A-D indicate that while the smaller particles 85, 98 eind 109 nm are indistinguishable from the dissolved solute, sodium dichromate, in as far as detector behaviour is concerned, the detector response differs significantly for the larger diameter particles. The reduced peak area and hence t irbi-dity indicated for the larger particles is a direct result of the optical effects noted earlier. The observations are consistent with the findings of Heller and Tabibian that the corona effect... 

The extension of the calibration curve beyond a retention vol ome of 58 ml poses less of a risk, in view of the acknowledged capacity of LEG in resolving small diameter particles, than in its extension to retention voliomes of less than U5 ml. The latter has the implication of counting particles as large as 2T8 nm (corresponds to a retention voliome of 38 ml see Fig. 8) which have earlier been shown to be totally trapped in the columns. 

Liquid chromatography/mass spectrometry (LC/MS) analysis Quantitation system Agilent Series 1100 liquid chromatograph Chromsep Omnispher 3 Cig HPLC column, 100 x 4.6-mm i.d., 3- am diameter particle size... 

Figure 1.14 Plot of plate height (mb) as a function of the nobile phase velocity ( 1/ain) for a series of colunns of 0.46 cm I.O. packed with a spherical porous n-octadecylsllanized silica of different particle diameters. For the 8 and 5 micrometer diameter particles the column length was 25 cm, for the 3 micrometer diameter particles IS cm and for 2 micrometer dieuaeter particles 4 cm. (Reproduced with permission from ref. 3. Copyright Elsevier Scientific Publishing Co.)...

The small peak volumes typical of samples eluted from small bore columns and short small diameter particle columns used in high-speed liquid chromatography place severe demands on the dispersion characteristics of all components of the liquid chromatograph. The standard deviation of a peak eluting from a column is given by... 

Li13 developed a method for the individual determination of caffeine and theobromine in cocoa beans. Cocoa bean samples are ground as finely as possible (less than 0.5-mm diameter particles), the powder is boiled in... 

The columns most commonly used at the moment are made from stainless steel tube with a 6.35 mm (1/4 inch) external diameter, a 4.6 mm internal diameter and up to 25 cm long. Most manufacturers offer a number of alternative lengths and diameters, eg lengths of 10, 12.5 or 15 cm and internal diameters of 3, 6.2 or 9 mm. The columns can be packed with 10, 5 or 3 pm diameter particles. 

The residence time is related to the number of turns (AO that the fluid makes in the vortex, which can vary from 0.2 to 10, with an average value of 5. If the 50% cut diameter particle is assumed to enter at (D — b)/2, with a residence time of... 

The most complete theory for aerosol coagulation is that of Fuchs (1964). Since the attachment of radon progeny to aerosols can be considered as the coagulation of radon progeny (small diameter particle) to aerosols (large diameter particle), it is reasonable to use Fuchs theory to describe this process. The hybrid theory is an approximation to Fuchs theory and thus can be used to describe the attachment of radon progeny to aerosols over the entire aerosol size spectrum. 

Figures 3 and 4 show the variation of the average attachment coefficient with CMD. It can be seen that for particles of CMD less than 0.06 ym and Og = 2 the kinetic theory predicts an attachment coefficient similar to the hybrid theory, whereas for CMD greater than about 1 ym the diffusion theory and the hybrid theory give approximately the same results. For a more polydisperse aerosol (Og = 3) the kinetic theory deviates from the hybrid theory even at a CMD = 0.01 ym. The diffusion theory is accurate for a CMD greater than about 0.6 ym. These results are easily explained since as the aerosol becomes more polydisperse, there are more large diameter particles (CMD >0.3 ym) which attach according to the diffusion theory. In contrast, the kinetic theory becomes more inaccurate as the aerosol becomes more polydisperse.

It is well known that enhanced deposition in the first few airways occurs due to the turbulence produced. Turbulent diffusion is accounted for by using factors (ratio of observed deposition to calculated diffusion deposition) to correct the diffusion deposition. These had formerly been measured by Martin and Jacobi (1972) in a dichotomous plastic model of the upper airways. The data used here are from measurements performed by Cohen (1986) using hollow casts of the upper bronchial tree which included a larynx. This cast was tested using cyclic flow with deposition measured for 0.03, 0.15 and 0.20 urn diameter particles. Her turbulent diffusion factors are used in the calculation here (14 for generation 0, and 2 for generations 1 to 6). 

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