Filters factors when selecting

The most commonly used filter medium is woven cloth, but a great variety of other media is also used. The main types are listed in Table 10.2. A comprehensive discussion of the factors to be considered when selecting filter media is given by Purchas (1971) and Mais (1971) see also Purchas and Sutherland (2001). Filter aids are often used to increase the rate of filtration of difficult slurries. They are either applied as a precoat... 

The choice of the solvent for a particular crystallization depends on several factors. The first, of course, is that it should dissolve, when hot, an appreciable amount of the substance to be purified without reacting chemically with it. In addition, the solvent should be relatively safe to handle (not poisonous or infiammable) and easy to remove from the filtered crystals. Some of the solvents most commonly used for crystallization are given in Table 1. The solvent is selected on the basis of solubility tests. One method of performing these tests is to place 0.1 g of the substance in a small test tube and then to add 1 ml of the warm solvent. If all the solid does not dissolve even on heating, then another ml of the solvent is added, and heat again applied. If a total of 3 ml is added and the substance does not dissolve when heated, then the substance is regarded as difficultly soluble in that solvent. Such a solvent is not suitable for crystallization, for it would require more than 100 ml of hot solvent to dissolve 2-3 g of the substance. Care should be exercised to distinguish small solubility from the presence of insoluble impurities. 

Many chemical component-s present in such aerosols are relatively stable they can be measured long after (days, week.s, or more) the aero.sol has been collected on a filter or impactor plate, for example. Short-lived reactive and/or volatile species such as peroxides and aldehydes are not usually determined. This may make it difficult to evaluate the health and ecological effects of aerosols because chemically reactive chemical species tend to be the most active biochemically. The chemical components present in the particles collected on a filter or impactor plate may react with each other when they are in close proximity. Particle deposits in filters or on surfaces may also react with molecular components of the gases flowing over them. Chemical reactions between the gas and aerosol may not affect mea.surement.s of metallic elements but may modify chemical speciation (compound form) on the collector surface. All of these factors must be taken into account in selecting sampling and measurement methods for aerosol chemical properties. 

In fact, several of the cigarettes which were machine smoked earlier and analyzed without precautions, when smoked by us under the same conditions but with precautions, yielded 25 to 100% lower values for DMN [A-nitrosodimethylamine] and NPY [V-nitrosopyrrolidine] for the mainstream smoke... The nitrate content of the tobacco appears to be a determining factor for the concentration of volatile nitrosamines in the smoke. Selective removal of these nitrosamines does occur with cellulose acetate filter tips but not with charcoal filter tips. 

The CMP process has a higher possibility of defects than other processes because it uses abrasive in slurry. It especially causes scratches therefore, controlling the defects is important. To repress scratches attributed to slurry, filter is generally placed at the supply system, circulation loop, and point of use (POU). These factors can be mixed diversely according to the polishing machine s structure or processing condition selection. However, other materials are also influenced because of the correlation when a factor... 

When employee exposure is identified, the employer can consider the respirators Assigned Protection Factors (APFs). The APFs are used to select equipment that will meet or exceed the required level of filter to protect the employee from the hazardous contaminant. 

Atom economy is used as the first filter to select suitable guanidine-catalysed enantioselective reactions. Most guanidine-catalysed reactions fit well with this criterion for example, Michael reactions and its variants have perfect atom economy when the guanidine catalyst is used as a Bronsted-base catalyst. Subsequently, we apply the E-factor to give a rough guide on waste generation of these selected reactions. 

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