Inert porous material

At high pressures, this reaction can occur explosively. For that reason, cylinders of acetylene do not contain the pure gas. Instead the cylinder is packed with an inert, porous material that holds a solution of acetylene gas in acetone. 

The separator is frequently a sintered glass frit, but it may also be any of a wide range of inert, porous materials such as celloton, vycor or porvic or an ion exchange membrane. A number of stable ion exchange membranes suitable for use in aqueous and non-aqueous solvents have become available in recent years. 

In both types of liquid-membrane ISEs, the membrane acts as an inunis-cible phase boundary between the aqueous and non-aqueous solutions inside the ISE (see the schematic diagram presented in Figure 3.13). In order to minimize mixing, the liquid membrane is held in place by an inert, porous material such as a rigid glass frit or a flexible synthetic polymer - the choice will depend on the manufacturer rather than on experimental considerations. 

The main argument for making MIP CEC is to combine the selectivity of the MIPs with the high separation efficiency of CEC. This argument appears to fail, however, if the adsorption isotherm of the MIP is nonlinear, which seems to be the rule. In the case of nonlinear isotherms, the peak shapes depend mainly on the isotherm, particularly so if the separation system is otherwise very efficient (has low theoretical plate height, see Fig. 1). In the case of ionized analytes the situation is more complex. If an ionized analyte is not adsorbed at all on the MIP, then it is separated only due to electrophoresis, and its peak will not be widened due to the nonlinear effect. In this case, however, the MIP is merely behaving like an inert porous material. In intermediate cases an ionized analyte may participate in both separation mechanisms and for this case we do not have exact predictions of the peak shape. 

As far as gas physics goes, there are only these two types of gases. However, the shipping industry has a third classification known as the dissolved gases. Acetylene is a dissolved gas, whic,h without special equipment, can explode at pressures above 15 psig. Because of this property, efficient shipping of this gas becomes almost impossible. To avoid this problem, the gas is shipped dissolved in acetone and placed in cylinders that are filled with an inert, porous material. Under these special conditions, acetylene can be safely shipped at pressures of 250 psig. 

Two distinct approaches have been adopted (a) the chemical attachment or tethering of the original catalytic species to a support material (applied mainly to reactions in the liquid phase), and (b) the physical absorption of the original soluble catalyst/solvent system into an inert porous material (applicable solely to gas-phase reactants and products). 

During SEC, polymer molecules in solution are separated according to hydrodynamic volume on a column packed with an inert porous material such as a highly cross-linked polymer or silica. Separation occurs because large molecules are unable to penetrate aU of the pores in the packing. Successively smaller molecules spend more time in the packing material and elute later. 

A salt bridge can be made from a strip of filter paper (or other inert porous material) soaked in a saturated solution of potassium nitrate. 

For the liquid junction potential to be well defined and stable with time, one must avoid contamination of the sample or bridge electrolyte by mixing from the other side of the junction. Junction materials are therefore chemically inert porous materials that block ccmvective mixing between the two compartments. They need to be chemically inert not to introduce surface charges that may act as ion-exchangers and hence result in undesired Donnan exclusion potentials. 

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

In heterogeneous catalysis, solids catalyze reactions of molecules in gas or solution. As solids - unless they are porous - are commonly impenetrable, catalytic reactions occur at the surface. To use the often expensive materials (e.g. platinum) in an economical way, catalysts are usually nanometer-sized particles, supported on an inert, porous structure (see Fig. 1.4). Heterogeneous catalysts are the workhorses of the chemical and petrochemical industry and we will discuss many applications of heterogeneous catalysis throughout this book. 

The retention mechanism of organic solutes by porous polymer beads remains ambiguous [478]. At low temperatures adso tion dominates but at higher temperatures the polymer beads could behave as a highly extended liquid with solvation interactions. The evidence for a partition mechanism is not very strong and its importance, at present, remains speculative. Like other adsorbents it has proven possible to control retention and enhance efficiency by diluting porous polymers with an inert support material (479). 

Small areas Small puddles of liquid can be contained by covering with absorbent material such as vermiculite, diatomaceous earth, clay, sponges, or towels. Place the absorbed material into containers lined with high-density polyethylene. Larger puddles can be collected using vacuum equipment made of materials inert to the released material and equipped with appropriate vapor filters. Wash the area with copious amounts of an alkaline soap/detergent and water. Collect and containerize the rinseate. Removal of porous material, including painted surfaces, may be required because these materials may be difficult to decontaminate. Ventilate the area to remove vapors. 

Darier Goudst (Ref 22) described a procedure for preventing expln of LA by effecting the reaction within the interstices of a porous inert absorbent material... 

In this chromatographic technique, the stationary phase is a liquid immobilised in the column. It is, therefore, important to distinguish between the inert support which only has a mechanical role and the stationary phase immobilised on the support. The impregnation of a porous material, the simplest way to immobilise a liquid, is abandoned when the mobile phase is a liquid because there is an elevated risk of... 

The dynamics of the molecules adsorbed in confined geometry is one of the most common and important research subject which has received much attention in the past few decades. Owing to the large polarizability and the chemical inert nature of the monoatomic xenon, the l29Xe NMR chemical shift is very sensitive to its environment and thus provides an ideal probe for the investigation of the structure of porous materials [1]. There have been numerous publications in this area since the pioneering works by Ito and Fraissard [2] and by Ripmeester [3], and several reviews have been attributed to related subjects [4-7]. Recent developments of the mesoporous MCM-41 materials [8] have also drawn intense attention due... 

The adsorbents in HPLC are typically small-diameter, porous materials. Two types of stationary phases are available. Porous layer beads (Figure 3.14A) have an inert solid core with a thin porous outer shell of silica, alumina, or ion-exchange resin. The average diameter of the beads ranges from 20 to 45 fim. They are especially useful for analytical applications, but, because of their short pores, their capacities are too low for preparative applications. 

The slider boat is usually constructed of graphite, although alternative materials such as boron nitride and silica (14) have been used. Graphite is readily obtained in high purity, easily machined, relatively inert with respect to the solution, and nearly frictionless in operation. Graphite boats do have a limited lifetime, and care must be exercised in desorbing gases contained in this relatively porous material. 

In order to improve the separating performance of HPTLC pre-coated plates silica gel 60 even at larger applied volumes, as may be necessary at low sample concentrations, and with a rapid and simple technique of application, HPTLC pre-coated plates silica gel 60 with so-called "concentrating zones" were developed (10, 11, 12). This type of plate consists of two distinct layer sections, namely the separating layer proper consisting of silica gel 60 and a concentrating zone composed of an inert, porous silicon dioxide. These two sorbent materials pass into one another at a clearly defined boundary-line in such a way that the eluant is offered no resistance as it passes through. 

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