Porous disk

In his work, Penefsky simply used 1 ml Plastipak tuberculin syringes fitted with porous disks cut with a cork borer (0.193 inch inside diameter) from polyethylene sheets (1.5 mm thick, 70 micrometer pore size) available from Bolab, Inc. (Deery, NH). Note The rubberized plungers of most syringes frequently contain lubricants, and these agents may bind to enzymes or they may dissolve and contaminate some enzyme preparations. 

Consider the opposed stagnation flow between two parallel porous disks that are separated by L = 2 cm. (e.g., Fig. 13.12). Air flows from one disk and methane flows from the other. Both inlet streams are at a temperature of T = 300 K and a velocity of u = 100 cm/s. If a flame is ignited, a strained diffusion flame is established between the... 

Coarse (dP = 50-100 pm) porous disks are the most frequently applied diffusers in large-scale drinking water treatment systems (Masschelein, 1994). They are seldom used in industrial waste water treatment applications. The reason is that blocking or clogging can easily occur, e. g. by means of precipitation of chemicals, like carbonates, aluminum or ferrous oxides, manganese oxides, calcium oxalate or organic polymers. This is also valid for ceramic filter tubes, which are sometimes used as mass transfer systems in drinking water applications. 

Much earlier, Friedman (IS) proposed that thermal conductivity was an important parameter in the correlation of quenching distance data. Weir and Morrison (43) spectroscopically traversed flat flames physically separated from a porous disk and found that the relative intensities of C2, CH, and OH were decreased as the amount of heat lost from the flame was increased. A large number of investigators have been concerned with... 

The experimental setup for the study of the equilibration reaction was completely analogous to that for the exchange reaction, with the exception that the amount of catalyst was a factor 103 smaller than before. This allowed measurement of reaction rates to be carried out at higher temperatures than maintained in the exchange reaction. The catalyst was applied in a thin layer on a porous disk in the reaction vessel. 

Figure 2.45). Bulk sorbent phases can also be purchased. Typical column housings are manufactured of polypropylene or glass, and the sorbent is contained in the column by using porous frits made of polyethylene, stainless steel, or Teflon. Pesek and Matyska [87] describe three types of disk construction (1) the sorbent is contained between porous disks, which are inert with respect to the solvent extraction process (2) the sorbent is en-... 

The porous plate measuring cell can be regarded as an appropriate development of the cell with porous disk, proposed earlier by Maysels and Jones [24,25] (Fig. 2.5). This disk is made of a sintered porcelain glued to a Perspex holder. A channel around the circumference of... 

Fig. 5. Schematic diagram of fluidized-bed reactor showing gas flow directions and details of the porous disk supporting the catalyst powder.

Galvanic cells can contain a salt bridge as in (a) or a porous-disk connection as in (b). A salt bridge contains a strong electrolyte held in a Jello-like matrix. A porous disk contains tiny passages that allow hindered flow of ions. 

Why is the use of a salt bridge or porous disk in a galvanic cell necessary ... 

An electrochemical cell consists of a nickel metal electrode immersed in a solution with [Ni2+] = 1.0 M separated by a porous disk from an aluminum metal electrode immersed in a solution with [Al3+] = 1.0 M. Sodium hydroxide is added to the aluminum compartment, causing AI(OH)3(s) to precipitate. After precipitation of Al(OH)3 has ceased, the concentration of OH- is 1.0 X 10-4 M and the measured cell potential is 1.82 V. Calculate the Ksp value for Al(OH)3. 

Polyprotic acid an acid with more than one acidic proton. It dissociates in a stepwise manner, one proton at a time. (7.7) Porous disk a disk in a tube connecting two different solutions in a galvanic cell that allows ion flow without extensive mixing of the solutions. (11.1)... 

A tube (20 cm. long and 2 cm. in diameter) with a porous disk (porosity 3 or medium) sealed in at one end and with an ungreased ground joint, is arranged as shown in Fig. 8. Rhodium(III) chloride 3-hydrate (11.0 g. 0.042 mol) is pulverized and placed on top of the disk. The apparatus... 

In chromatographic separations using flat sheet membranes, compact porous disks, fibers, tubes, or rods, the interaction between the ligate molecule and the immobilized ligand takes place in the through-pores of the matrix and not in the dead-end pores of the conventional packed-bed particles. This method resembles affinity membrane separation with a very short affinity chromatography column [2]. 

Strancar, A. Koselj, P. Schwinn, H. Josic, Dj. Application of compact porous disks for fast separations of biopolymers and in-process control in biotechnology. Anal. Chem. 1996, 68 (19), 3483 -3488. 

Porous glass is used as substrates for immobilization of enzymes, for porous disks for electrodes, and as a precursor for Vycor (96% Si02) brand glass. The latter is a result of consolidation of the porous glass at 1000°C. 

For eaeh leaching experiment, a core was removed from the freezer and the plastie eaps on each end of the eore were replaced with thick-walled rubber eaps eontaining inlet and outlet ports and a 2-mm-thick porous disk to ensure an even flow of eluent across the core surface. Nylon-mesh filter disks were placed inside each cap to contain the aquifer solids. The eore was allowed to thaw for three days and reaeh room temperature ( 22°C) prior to leaehing. 

TPSR Characterization of Deposited Carbon. In an experiment to analyze the TPSR characteristics of a carbon deposit, 15 to 35 mg of powdered (170/250 Tyler mesh) catalyst was placed on the porous disk of a quartz microreactor. Typically, a fresh sample of catalyst was reduced for 15 hr at 773 K in 1 atm flowing H2 and a previously reduced catalyst was heated to 773 K for at least 1 hr before a TPSR experiment. Following reduction, the catalyst was flushed with pure He and cooled or heated to a predetermined carbon deposition temperature. Carbon was deposited by exposure to a stream of dilute hydrocarbon (typically 0.14-vol% C2H4) in helium using a special 10-port switching valve (Figure 1). Following carbon deposition, the catalyst was cooled to room temperature while the bed was flushed with pure He, and the He carrier (now in reactor by-pass mode) was replaced by the TPSR reactant gas stream (1-atm Hj or 0.03-atm H2O in He). After the... 

A common check valve design is to have a small synthetic ruby bead contained in a small cylinder that composes the check valve. On one end of the cylinder there is a centrally perforated funnel-like ceramic disk on which the bead can seat and block liquid flow. At the other end of the check valve, the ball can seat on a small ceramic highly porous disk (Figure 11.11). In the inlet check valve, as the piston enters the chamber and pressurizes the mobile phase, the bead will seat on the funnel-like disk and prevent any back-flow while the outlet check valve will open and allow the mobile phase to be forced through the column. As the piston is withdrawn from the chamber, backpressure will cause the outlet check valve to close and allow fluid to enter the piston chamber from the solvent reservoir via the inlet check valve. The cycle then repeats. 

Several types of equipment are available for laboratory use and for commercial UF installations. Small samples may be processed with flat circular membranes supported on a porous disk in a cylindrical cell. A magnet-driven stirrer above the membrane provides crossflow of the solution. Rectangular cells can also be used with solution recirculated through the small gap between the membrane and the top of the cell. These devices are useful for preliminary tests, but performance data are not directly applicable to large units. 

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