Test gases, potential differences

Under carefully optimized conditions (internal flow rates, temperature, switch time, feed concentration and enantiomeric excess ee) the enantio-selective SMB-GC pilot unit furnished a total of 20 g of each enantiomer of enflurane with an enantiomeric excess of 96.6 % (time requirement not known) with N2 as carrier gas (Biressi et al., 2002b). Noteworthy is the low particle size of the non-acid-washed Chromosorb A (NAW) used ( 0.6 mm). Enflurane was introduced in the gaseous form (saturated in N2). The SMB-GC unit produced the largest amounts of single enflurane enantiomers presently available for testing of potential differences in biological activity. No comparison of throughput between the batchwise vs. the SMB process is as yet available. 

Because it is inconvenient to bubble H2 gas through a solution, a more sophisticated pH meter is used in standard laboratory practice. Dilute hydrochloric acid is used as the reference solution. The test solution is in contact with a thin glass membrane in which a silver wire coated with silver chloride is imbedded. This glass membrane is dipped into the test solution and the potential difference between the solutions is measured and interpreted by a computer, which displays the pH of the test solution. The same equation holds for both pH meters. 

Figure 25-1 Potential differences measured on the cells air, Pt 1 Zr gg Mg u O, gg 1 Pt, test gas, formed with a solid electrolyte tube as shown in Figure 25-25. The test gases were ([67]) ...

Ceramic materials that retain structural integrity to temperatures in the 2100 to 2400°F range have been the subject of research and development for many years. Researchers have in fact created small radial inflow turbines from structural ceramic material for possible use in automotive gas turbines. These experimental units have shown favorable properties in laboratory tests. However, several practical considerations pose potential stumbling blocks to their use in commercial systems, such as coefficients of expansion that are substantially different from those of the metals used in gas turbine construction. One may expect to find ceramic materials in use in industrial gas turbines in the future, first on... 

For interfacial systems, potential functions should ideally be transferrable from the gas-phase to the condensed phase. Aqueous-mineral interfaces are not in the gas phase (although they may be close, see (7)), but both the water molecules and the atoms/ions in the substrate are in contact with an environment that is very different from their bulk environment. The easiest different environment to test, especially when comparing with electronic structure calculations, is a vacuum, so there is likely to be a great deal of information available on either the surface of the solid or the gas-phase polynuclear ion or the gas-phase aquo complex (i.e., Fe(H20)63+, C03(H20)62-). The gas-phase transfer-ability requirements on potential functions are challenging, but it is difficult to imagine constructing effective potential functions for such systems without using gas-phase systems in the construction process. This means that any water molecules used on these complexes must also transfer from the gas phase to the condensed phase. A fundamental aspect of this transferability is polarization. 

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