Electrical conductivity measurement procedure

Additional checks were made using a dialysis procedure in which zeolite samples which had been isotopically equilibrated with a 22Na O.OlAf NaCl solution were dialyzed against distilled water. After repeated washings, the sodium loss from NaX reached a steady value of 2.8 ( 0.1) ions/ unit cell at a zeolite content of 0.44 gram/liter, i.e. a value which is nearly identical to the data in Table I for a 10 NaCl concentration. Under similar conditions, the sodium loss from NaY is much less and corresponds to 1.5 ( 0.1) ions/unit cell. These results were confirmed by electrical conductivity measurements on the respective dialysates the conductivity for NaX is about twice as large (7.5 X 10 6 mhos/cm) as for NaY (3.9 X 10 6 mhos/cm). 

If this procedure is not foimd to be reliable one could perform a direct calibration at high temperature by resorting to the available high precision data for the conductivity of KCl solutions up to 410 °C and 33 MPa (Ho et al, 2000). This data are more precise than those reported in 1970 for aqueous 0.01 demal KCl solutions as reference solutions for electrical conductance measurements to 800 °C and 1200 MPa. (Quist el al, 1970). 

Electrical and thermal conductivity are important diffusion layer properties that affect the fuel cell s overall performance. The maferial chosen to be the DL in a fuel cell must have a good electrical conductivity in order for the electron flow from the FF plates to the CLs (and vice versa) to have the least possible resistance. Similarly, the DL material must have good thermal properties so that heat generated in the active zones can be removed efficiently. Therefore, in order to choose an optimal material it is critical to be able to measure the electrical and thermal conductivity. In this section, a number of procedures used fo measure fhese paramefers will be discussed. 

The example selected here shows the techniques developed by Szwarc s group (Bhattacharyya, Lee, Smid and Szwarc, 1965). They eschewed completely the use of taps and in each experiment the electrical conductivity and the optical absorption of the solution were measured this actually involves the same combination of devices as the Pask-Nuyken and Holdcroft-Plesch reactors described in Section 3.2.2. The description of the procedure is taken almost verbatim from the original publication, whose conciseness cannot be bettered. 

Even more interesting and important than the foregoing unique method of measuring thermal conductivities of suspensions is the procedure used to calculate thermal conductivities theoretically. Orr and DallaValle noted that electrical and thermal fields are similar hence the usual equation for calculation of electrical conductivity of a suspension should also be applicable to thermal conductivities. Their extensive tabulated results support this contention to within 3 %. This equation is... 

Critical micelle concentrations can be determined by measuring any micelle-influenced physical property as a function of surfactant concentration. In practice, surface tension, electrical conductivity and dye solubilisation measurements (see Figure 4.13 and page 90) are the most popular. The choice of physical property will slightly influence the measured c.m.c., as will the procedure adopted to determine the point of discontinuity. 

When the procedure involves measurement of the electrical conductivity of the film, vessel 3 is filled up with the solution. The rings are wetted by the solution and when drawn... 

The nature of the tracer dictates the detection system. For the liquid phase, quite often the tracers (e.g., NaCl, H2S04, etc.) are such that the detection probe is directly inserted into the reactor and continuous monitoring of the concentration at any fixed position is obtained by means of an electrical conductivity cell and a recorder. In this case, no external sampling of liquid is necessary. If the tracer concentration measurement requires an analytical procedure such as titration, etc., sampling of the liquid is required. For the solid phase, a magnetic tracer is sometimes used. The concentration of a solid-phase tracer can also be measured by a capacitance probe if the tracer material has a different dielectric constant than the solid phase. In general, however, for solid and sometimes gas phases, some suitable radioactive tracer is convenient to use. The detection systems for a radioactive tracer (which include scintillation counters, a recorder, etc.) can be expensive. Some of the tracers for the gas, liquid, and solid phases reported in the literature are summarized in Table 3-1. 

Solvent purification has been discussed by many, and recommended procedures have been listed by Kratochvil. Molecular and volatilizable impurities are best measured by gas chromatography, and ionic impiuities by electrical conductivity. The commonest and most troublesome impurity, because of its leveling action, is water it can be measured by the Karl Fischer method (Section 19-8) among others. 

Two experimental procedures were carried out. In the first, a 100 1 (water and dye filtrate) dilution was concentrated to one-tenth its initial volume. Rejection based on color absorbance (HlO nm) and electrical conductivity, flux, pressure, temperature, and crossflow rate were measured at intervals during the concentration experiment. In the second, a slightly diluted dye filtrate (2 3) was used and the hyperfiltration at steady state was evaluated as in the first procedure. The test was repeated at dilutions reaching (100 1), with pH and temperature excursions at a dilution of 3 1. 

In this work, an attempt was made to prepare IrSbs by liquid-solid phase sintering (LSPS) and hot pressing of pulverized LSPS powders. The LSPS powder were characterized by using an X-ray diffractometer. These procedures were also applied to form an IrSbs-CoSba solid solution. The electrical conduction parameters of these materials were examined on the electrical measurement. The thermal stability of the hot-pressed IrSbs was also investigated. 

Procedure Measure and compare electrical conductivity of listed solutions. Dilute the solutions, test and compare with conductivity of mineral water, tap water and distilled water. 

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