Positive electrode ports

Some of these parts, such as the threads on the pipe nipple, may have burrs on them, or shavings of metal that were not completely removed in the threading process done by the manufacturer. Pull these off, or grind them, or file them down. Inspect all parts as you receive them and finish working on them, and remove any such imperfections. 

Pipe nipple for electrolyzer body, drilled and tapped 

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After the liner is trimmed, slip it into the nipple. The position of the liner s seam when placed in the nipple should be 90° from each positive electrode port hole in the nipple (halfway in between them). Mark the position of the holes through the pipe nipple. 

Coat two 34" NPT x 3/a" Yor-Lok fittings on the 34" NPT side with thread seal, and tape with Teflon. Screw these into the positive electrode port holes and tighten. 

Cut four silicone rubber rib spacers Vs" thick, by /4" wide, by 6" long. Cement these strips with silicone or epoxy to the inner walls of the electrolyzer chamber more or less equidistant from each other, with one end of the strip lining up with the bottom edge of the pipe. Be sure not to cover over the positive electrode port... 

Mark the port holes for the positive electrode assembly on liner... 

Slip the cylinder back into the pipe and position the overlapping seam over one of the electrode port holes. Inside the tube, place your fingers over that hole, and press the mesh against the pipe. 

A schemahc diagram of the DEMS apparatus is shown in Fig. 5. The electrochemistry compartment corrsists of a circular block of passivated htanirrm (a) that rests above a stainless-steel support (1) cormected to the mass spectrometer. The space between the cell body and the snpport is a Teflon membrane (j) embedded on a steel mesh (k) the membrane is 75 pm thick, has 50% porosity and pore width of 0.02 pm. The single-crystal disk (h) is the working electrode its face is in contact with the electrolyte solution and separated from the cell body by another Teflon membrane (i) that functions as a spacer to form a ca 100-pm thick electrolyte layer (j). Stop-flow or continnons-flow electrolysis can be performed with this arrangement. For the latter, flow rates have to be minimal, ca 1 pL/s, to allow ample time (ca 2 s) for the electrogenerated products to diffuse to the upper Teflon membrane. Two capillaries positioned at opposite sides of the cell body (b, e) serve as electrolyte inlet and outlet as well as connection ports to the reference (f) and two auxiliary Pt-wire electrodes (d, f). 

OCN), which is a variation of the pneumatic concentric nebulizer built from flexible capillary mbes, was used in an interface. The OCN has had little application in CE interfaces, owing to its generally lower sensitivity performance when compared to other pneumatic nebulizers used with ICP-MS detection.The direct injection nebulizer (DIN), previously described in The Nebulizer, was used by Liu et al. in a CE interface. The electrophoretic capillary was directly inserted through the central sample introduction capillary of the DIN. A platinum grounding electrode was positioned into a three-port connector. This connector contained the DIN sample introduction capillary as well as a make-up buffer flow. These alternative nebulizers have been successfully used in CE interfaces, but the pneumatic designs dominate the interface systems reported in the literature. 

In Fig. 4.68 is shown a microconduit incorporating two potentiometric pH electrodes and a common reference electrode, the introduction of sample solution being executed by means of an exteriorly placed injection port. The measurement of pH requires a system with limited dispersion coefficient, and no chemical reaction is needed in the flow channel. Consequently, a short residence time was chosen, and the two pH-sensitive PVC-based membrane electrodes, containing as electroactive material tri- -dodecylamine [778], were placed in a single-line system and very close to the injection position (cf. Fig. 4.3), the Ag/AgCl wire reference electrode being situated in a side channel and connected to the main channel downstream from the indicator electrodes. The manifold construction is such that the reference solution and thus the liquid junction are renewed... 

The positive lead of the single-fiber electrode (see Figure 25.6) is the end cap of a 25-/xm wire exposed through a side port on the cannula of a steel needle. Due to the small size of the positive lead, bioelectric sources, which are located more than about 300 /xm from the side port, will appear as common-mode signals and be suppressed by the differential amplifier. To further enhance the selectivity, the recorded signal is high-pass filtered at 500 Hz to remove low-frequency background activity from distant fibers. 

The microfluidic fuel cell concept was first invented and demonstrated in 2002 [5, 6]. As shown schematically in Fig. 1.1a, b, the original cell design introduced two reactants (fuel and oxidant) through separate inlet ports into a single microfluidic channel with electrodes (anode and cathode) patterned on the channel walls. In microfluidic channels, mixing of two parallel laminar streams is minimal, and reactant crossover can be avoided by strategic electrode positioning sufficiently far... 

The construction of flat-plate prismatic cells is illustrated in Fig. 35.35. As in a wound cell, a microporous polyethylene or polypropylene separator separates the positive and negative electrodes. Typically each plate in the cell has a tab, the tabs are bundled and welded to their respective terminals or to the cell case. Cell cases of either nickel-plated steel or 304L stainless steel have been used. As shown, the cover typically incorporates one or two terminals, a All port and a rupture disk. The terminal may be a glass-to-metal seal, for low cost applications compression type seals have been used, or the terminal may incorporate devices similar to those found in the header of cylindrical products to provide pressure, temperature and over current interrupt in one component. The case to covo" seal is typically formed either by TIG or laser welding. 

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