Micronized solid particles

The data in Fig. 7 demonstrate that in the presence of 15 micron solid particles, there is a slight or moderate impact on destruction kinetics. The destruction rate constant of trichloroacetonitrile (TCA) decreases by approximately 10% when the silica particle concentration is increased from 0 to 100 g L 1. In the presence of 10 nm silica (Fig. 8), the trends are similar, with slight to moderate decreases in the reaction rate constant as the silica particle concentration increases. 

A typical process for the production of vitreous-carbon spheres is represented schematicctlly in Fig. 6.9.1 The precursor is a partially polymerized polymer such as furfuryl alcohol, catalyzed with p-toiuene sulfonic acid and mixed with acetone to obtain the proper viscosity for atomization.l l A pore former is added which can be an organic material with a high boiling point or sub-micron solid particles such as carbon black. Atomization occurs in the thermal reactor shown schematically in Fig. 6.10.1 The curing time is very brief because of the small size of the particles ( 45jum). 

Water-borne wood preservatives, based on hinokitol and crude tall oil have been patented. The solubility of aetive ingredient has been enhanced by addition of base. Hydrocarbon solvent is used in composition comprising an ester of boric acid and pen-tachlorophenol." Ester is used as cosolvent capable to dissolve active component. Also, micronized solid particles of preservative can be suspended in liquid organic carrier, such as toluene, xylene, mineral oil, vegetable oil, etc. ... 

In general, when sepiarating two liquids, they must be immiscible and have different spiecific gravities before a separation technique-such as oil/water separation-would be effective. In the case of finely dispersed liquids or finely dispersed solids, if the dispersed material is below one micron in particle size, centrifuging should be considered. The use of centrifugal force on the differing densities of the material can facilitate the separation technique. 

In the emulsion polymerization of vinyl chloride (VC) initiated with type II MAI composed of PDMS, block efficiency was as high as 95-97%, and solid particles with a narrow range of particle size, 0.1-50 microns, were obtained in high yield [15]. 

Chemically inactive These are made from a variety of materials that include wound yarn, felt, flannel, cotton waste, wood pump, mineral wool, asbestos and diatomaceous earth. The solid particles are trapped and retained within the medium. Certain types will remove water, as well as large and small particles of solids in a range down to 10 microns. Ceramics are sometimes employed for depth filtration, as also are special sintered metals. 

Returning now to the subject of the chapter, in addition to appropriate retentive characteristics, a potential stationary phase must have other key physical characteristics before it can be considered suitable for use in LC. It is extremely important that the stationary phase is completely insoluble (or virtually so) in all solvents that are likely to be used as a mobile phase. Furthermore, it must be insensitive to changes in pH and be capable of assuming the range of interactive characteristics that are necessary for the retention of all types of solutes. In addition, the material must be available as solid particles a few microns in diameter, so that it can be packed into a column and at the same time be mechanically strong enough to sustain bed pressures of 6,000 p.s.i. or more. It is clear that the need for versatile interactive characteristics, virtually universal solvent insolubility together with other critical physical characteristics severely restricts the choice of materials suitable for LC stationary phases. 

The USP has numerous requirements, e.g., ophthalmic solutions [need be] essentially free from foreign particles, suitably compounded and packaged for instillation into the eye, or ophthalmic suspensions [need contain] solid particles dispersed in liquid vehicle intended for application to the eye [1]. Ophthalmic suspensions are required to be made with the insoluble drug in a micronized form to prevent irritation or scratching of the cornea. A finished ophthalmic ointment must be free from large particles and must meet the requirements for leakage and for metal particles under ophthalmic ointments . These and other requirements will be discussed further in subsequent sections. 

Figure 49 shows a set of bed collapsing curves for a Geldart Group A-A (for Geldart s classification of solid particles, see Geldart, 1972, 1973) binary solids mixture, two closely sized alumina powders, of average particle diameter 104 and 66 microns, respectively. The curve on the extreme left with 0% fines represents the pure coarse component, which is... 

Smokes from hydrocarbon fires consist of liquid or solid particles of usually less than one micron in size, suspended in the combustion gases, which are primarily nitrogen, carbon monoxide and carbon dioxide, existing at elevated temperatures. At normal temperatures carbon is characterized by a low reactivity. At high combustion temperatures, carbon reacts directly with oxygen to form carbon monoxide (CO) and carbon dioxide (CO2). 

Aerosols Minute liquid and solid particles that are suspended in the atmosphere. Sizes range from 0.001 to 100 microns in diameter. 

Drugs can be sprayed in aerosol form onto mucosal surfaces of body cavities accessible from the outside (e.g., the respiratory tract [p. 14]). An aerosol is a dispersion of liquid or solid particles in a gas, such as air. An aerosol results when a drug solution or micronized powder is reduced to a spray on being driven through the nozzle of a pressurized container. 

Dust may be defined as suspension in air or other gases, of small solid particles ranging from ca 0.05 to 1000 microns in size. Mrs is usually water or other liq in the form of particles floating or falling in the atmosphere. Vapor is a term applied to a gas that is at a temp below its critical temp, which can, therefore, be condensed by pressure alone... 

Dry Powder A tenn applied to the extinguishing agent suitable for use on combustible metals. Dusts Solid particles generated by mechanical processes such as crushing and grinding, without any chemical change from the paren material. Their size range is typically between 0.1 and 100 microns. 

Fully Encapsulating Suit (FES) Sometimes referred to as a Moon Suit, personal protective clothing diat provides complete skin, eye, and respiratory proteetion, and includes positive-pressure SCBA. The reader should refer to Chapter 2 for detailed discussions. Refer to Protective Materials. Fumes Solid particles formed by the condensation of vaporized solids, usually molten metals. Particles are much smaller than dusts with typical size ranges between 0.01 and 1.0 microns. Functional Group An atom or group of atoms, bound together chemically, that has an unpaired electron, which when it attaches itself to the hydrocarbon backbone, imparts special properties to the new compound thus formed. 

The principles of particle stabilization are even more critical to the stabilization of very small solid particles, less than one micron in diameter (e.g., nanosuspensions), which have much greater surface area. The Ostwald-Freundlich equation,... 

The substance which has to be micronized is filled into a thermostatted feed vessel (A) (Figure 9.8-6). The solution from (A) is transferred into the thermostatted autoclave (C) after evacuation. The compressible medium is supplied by a high-pressure pump (B). The pressure in the autoclave is increased to a certain value, and the high-pressure circulation pump (D), connected with the autoclave, is installed to increase the efficiency of dissolving of the solute by circulating the liquid phase. The gas-saturated mixture is rapidly depressurized through a nozzle. In the spray-tower the solvent is set free, and the formed solid particles of the substance under consideration (>10 pm) are collected in the vessel at the bottom. The temperature in the spray can be measured and recorded via two thermoelements. 

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. 

The size distribution of radioactive compounds was studied by Leary and Fitzgibbon (38, 39), who used radioautographic techniques. The method is especially useful for solid particles in the size range of 0.1 to 10 microns and may have limited application, as a research tool only, in the study of fuel sprays. 

It has to be kept in mind that particulate materials are dispersions. In fact, the classical powder is a concentrated dispersion of solid particles in air. At a very low concentration, very Lne particles (micron, submicron size) can form an aerosol. In such a case-ewing to the large interparticulate distance-fhe particle-particle interactions can be neglected. In general, a particle can exhibit a substructure, that is, a particle may have external and internal pores. An external pore can be related to the roughness of the surface of a particle. 

Experiments to distinguish between these two possibilities have often involved measurements of ultrasonic attenuation (ref. 5,9,31,32). The popularity of this approach derives in part from the fact that small impurities in liquids, such as suspended particles, have negligible influence on attenuation in comparison with even a very small concentration of microbubbles (ref. 9). (Microbubbles, in contrast to solid particles, appreciably increase the compressibility of a liquid, introducing forms of viscous losses and nonreversible energy exchanges that do not exist in the case of solid particles.) It is therefore of considerable interest that all fresh tap water samples measured by Turner (ref. 9) showed substantial and persistent abnormal (ultrasonic) attenuation, amounting to a minimum of 44% over that of distilled water it was concluded that this result stemmed from the presence of stabilized micron-sized bubbles. 

The sol-gel process involves first the formation of a sol followed by that of a gel. A sol, which is a liquid suspension of solid particles ranging in size from 1 nm to 1 micron, can be obtained by the hydrolysis and partial condensation of a precursor such as an inorganic salt or a metal alkoxide. The further condensation of sol particles into a three-dimensional network produces a... 

It is interesting to note that Heyraud and Metois found that small, micron-size, solid particles of Au (Heyraud and Metois 1980) and Pb (Heyraud and Metois 1983) assumed equilibrium shapes at high temperatures on monocrystalline... 

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