Plug porous

The rigid wall is stiff. When pressure is applied, it does not change its shape and size. If a thermodynamic system is enclosed in a rigid wall, its volume remains constant, i.e., it ensures that d V = 0 under any change of the thermodynamic variables of the system. 

The diathermic border has no volume. So it cannot take up volume energy. The diathermic border faces a temperature Th from one surface and a temperature Ti from the other surface. Here Th 7]. When entropy d5(7/,) passes into the border across a surface, the diathermic border ejects -d5(7]) at the opposite surface following the relation 

In this way, the diathermic border is a generator for entropy, even when it cannot store entropy. Moreover, the diathermic border acts as a valve for entropy. If 7), 7] then it does not allow an inflow of entropy, d CT),). 

the porous plug in the Joule - Thomson experiment is an idealized device. It has certain properties, such as lack of volume, common to the diathermic border, but it does not allow a flow of entropy without flow of matter. When matter flows though the porous plug, the pressure and the temperature are reduced. This is associated with an increase of entropy. 

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Streaming potentials, like other electrokinetic effects, are difficult to measure reproducibly. One means involves forcing a liquid under pressure through a porous plug or capillary and measuring E by means of electrodes in the solution on either side [6, 23, 71-73]. 

If the solid in question is available only as a finely divided powder, it may be compressed into a porous plug so that the capillary pressure required to pass a nonwetting liquid can be measured [117]. If the porous plug can be regarded as a bundle of capillaries of average radius r, then from the Laplace equation (II-7) it follows that... 

Bartell and co-workers report the following capillary pressure data in porous plug experiments using powdered carbon. Benzene, which wets carbon, showed a capillary pressure of 6200 g/cm. For water, the pressure was 12,000 g/cm, and for ben-... 

To appreciate the questions raised by Knudsen s results, consider first the relation between molar flow and pressure gradient for a pure gas flowing through a porous plug, rather than a capillary. The form predicted by the dusty gas model can be obtained by setting = 1, grad = 0 in equation... 

A typical Ag/AgCl electrode is shown in figure 11.9 and consists of a silver wire, the end of which is coated with a thin film of AgCl. The wire is immersed in a solution that contains the desired concentration of KCl and that is saturated with AgCl. A porous plug serves as the salt bridge. The shorthand notation for the cell is... 

From Fig. 10.40 it will be seen that contact between the electrolyte (soil or water) and the copper-rod electrode is by porous plug. The crystals of CUSO4 maintain the copper ion activity at a constant value should the halfcell become polarised during measurements. The temperature coefficient of such a cell is extremely low, being of the order of 1 x 10" V/°C and can thus be ignored for all practical purposes. To avoid errors due to polarisation effects, it is necessary to restrict the current density on the copper rod to a... 

Figure 3.5 In the Joule-Thomson expansion, a volume of gas V, is pushed through a porous plug by a piston at pressure pt. The gas expands to a volume V2 against a second piston at a pressure p2.

What is the molar mass of a compound that takes 2.7 times as long to effuse through a porous plug as it did for the same amount of XeF, at the same temperature and pressure ... 

A sample of argon gas effuses through a porous plug in 147 s. Calculate the time required for the same number of moles of (a) CO, (b) C2H4, (c) H2, and (d) SO, to effuse under the same conditions of pressure and temperature. 

A hydrocarbon of empirical formula C,H, takes 349 s to effuse through a porous plug under the same conditions of temperature and pressure, it took 210. s for the same number of molecules of argon to effuse. What is the molar mass and molecular formula of the hydrocarbon ... 

When a parison or preform is inflated, it displaces the air around it within the mold. If no provision is made to vent the mold, compression of the air around the parison or preform can raise its temperature to such an extent that it can scorch the surface of the product. To avoid this problem, we equip blow molds with vents. These can consist of slit vents at the parting line between mold halves, porous plugs of sintered metal, or small holes drilled into the cavity walls. 

This consists of a silver wire, coated with silver chloride and in contact with a solution of potassium chloride saturated with silver chloride. The solution is contained in a tube, the end of which is sealed with a porous plug or disc to facilitate contact with the sample solution. The half-cell and associated electrode reaction is represented by... 

Some electrodes are double-junction electrodes. Such electrodes are encased in another glass tube and therefore have two junctions, or porous plugs. The purpose of such a design is to prevent contamination—the contamination of the electrode solution with the analyte solution, the contamination of the analyte solution with the electrode solution, or both, by the diffusion of either solution through the porous tip or plug. See the next section for tips concerning these problems. 

The Ti02 electrode was placed in an alkaline solution and the Pt counter-electrode was immersed in an acidic solution, with the two solutions being separated by a porous plug to prevent mixing (Figure 11.8). 

Figure 4.4 The saturated calomel electrode. A platinum wire makes electrical contact with an electrode which is composed of a paste of metallic mercury, mercuric chloride (calomel) and potassium chloride. A saturated solution of potassium chloride completes the half-cell and provides electrical contact through a porous plug.

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