Perforated electrodes

A comparable cell design - but with flat, solid, or perforated electrodes, mounted parallel nearby the diaphragm - avoids the above-mentioned problems and can work with optimal current distribution [84]. 

Figure 12.7b is a sketch of an apparatus that may be used to measure streaming potential. As was the case with electroosmosis, the capillary can be replaced by a plug of powdered material between perforated electrodes. An applied pressure difference p across the capillary causes the solution to flow through the capillary, thereby tangentially displacing the part of the double layer in the mobile phase from the stationary part. 

Silicic acid,1 in a form which is soluble and chemically pure, can be obtained by employing a divided cell with alkali silicate in the anode compartment. Perforated electrodes are fitted against the diaphragm wall, and during electrolysis alkali diffuses into the cathode compartment whilst silicic acid remains in the anode compartment. Hydrated silica is thus separated in a pure form specially suitable for stabilising colloids. 

In another process for the electrolytic lixiviation of animal, vegetable, and mineral substances,3 electrically active material is extracted by causing the liquor, in which the substance is suspended, to travel backwards and forwards through perforated electrodes. The negative and positive constituents collect at their respective electrodes. 

Electrolyzers with louvre type, lamellar, or perforated electrodes. 

Another cell design strictly directed toward minimization of the ohmic drop in the electrolyte, especially if gases are developed at the electrodes, is the zero-gap cell, shown in Fig. 8 [17, 93, 94]. The perforated electrodes are pressed directly onto the diaphragm by the current collectors providing optimum contact across the whole electrode area. However, uneven... 

Transmission Cells Using Optically Transparent or Perforated Electrodes... 

A plasma beam is formed by passing a suitable gas mixture through a pair of perforated electrodes which confine the r.f. discharge. Figure 1 shows the physical layout schematically. 

This correlation (and others) requires no knowledge of bubble size and is applicable to systems with an approximately uniform voidage distribution. Bubbles may cause a considerable effect by accumulating near the vicinity of the gas-evolving electrode and producing an electrolyte layer rich in gas bubbles, the bubble curtain effect. This layer can be as thick as a few millimeters if not controlled, it can be a major source of ohmic resistance. The usual way to meet this problem is to induce effective electrolyte circulation and/or to use perforated electrodes. The latter are used in chlorine electrolyzers in order to permit gas release at the rear, away from the potential field. 

Forced convection is used to prevent excessive buildup of gaseous products in the interelectrode space. Another approach is to allow release of gas behind the electrodes by using meshed or perforated electrodes. These devices have been used successfully in modern chloralkali cells and have the advantage of allowing narrow gaps between the electrodes. They can have, however, some disadvantages, since contours on the electrodes can cause nonuniformities in current distribution. Also, the open areas for gas release may cause higher current densities in operation, with a possible adverse effect on electrode life. 

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