Closed measuring cell

The Rubotherm system provides gravimetric sorption measurements carried out in a closed measuring cell completely thermostated up to 700 K or down to 77 K without temperature differences or corrosive parts inside the whole measuring cell with pressures up to 100 MPa and a mass sensitivity down to 1 gg using a magnetic suspension balance to measure mass transfer under controlled environments (14). 

Measurement of chemical parameters is best accomplished with an in-line closed measurement cell (25). When the values of the indicator parameters are observed to vary less than +10% over three consecutive well-bore storage volumes, the well may be presumed to have been adequately flushed for representative sampling. When in-line measurement cells are not practical, standard pH and conductivity meters and thermometers are used. 

Fig. 2. The oscillating bubble (drop) system with a closed measuring cell and excitation by the pressure change at the external end of the capillary I -capillary, 2 - phase A (solution), 3 - phase B (gas or liquid), 4 - pressure transducer.

Let us consider a closed measuring cell filled with a surfactant solution and the bubble or drop formed on the tip of a capillary submerged into this solution (Fig. 4). In equilibrium the pressure difference between the solution (phase A) and the external gaseous or liquid phase (phase B) is compensated by the Laplace pressure of the meniscus of the surface which is covered by the equilibrium surfactant layer. 

In this set-up, a temperature-controlled closed measuring cell is filled with a liquid or a surfactant solution as a first liquid. After a small drop of a second liquid is formed at the tip of a narrow capillary immersed in the cell, the drop volume, and consequently the drop area and radius, are subjected to sinusoidal oscillations via a piezelectric transducer connected to the measuring cell. Through changes in the drop radius, a sinusoidal... 

Before measuring conductivity, carbon materials and their mixtures were dried to residual moisture content of less than 5wt%. A sample of the investigated material was put into a measuring cell, representing a dielectric cylinder closed at both ends by the measuring electrodes. 

The highly conjugated diketo system obtained as a result of irradiation of the stilbosterol solution placed in a closed spectrophotometer cell for a duration of 10 minutes and exposed to a 15-watt short-wave ultraviolet lamp. Ultimately the extinction is duly measured at 418 nm and compared with stilboesterol (RS) treated exactly in the same manner. 

Procedure Weigh accurately about 20 mg of stilbosterol in sufficient ethyl alcohol to produce 100 ml and dilute 10 ml of this solution to 100 ml with ethyl alcohol. To 25 ml of the resulting solution add 25 ml of dispotassium hydrogen phosphate solution, transfer a portion of the mixture to a 1-cm closed quartz cell, place the cell 10 cm from a 15 watt short-wave UV-lamp, and subject it to irradiation for 10 minutes. Now, measure the extinction of the irradiated solution at the maximum at about 418 nm as described earlier. 

This is the correct expression for use in the analysis of closed diffusion-cell experiments for the measurement of diffusion coefficients. Equation (48) is known as Fick s First Law of Diffusion. Note that Na = — NB corresponds to saying that w = 0. 

The instrument works in a semi-continuous way. First, the pump purges the sample lines and the measurement cell in order to flush out the old sample and bring in the new one. The valves to and from the measurement cell are then closed and measurement starts the IR source is turned on, the chopper wheel starts rotating and the microphones pick up the photo-acoustic signal. The optical filter wheel positions each of the optical filters in the light path, one after the other, until all filters have been measured. Finally the instrument calculates the concentration of each gas, the results are displayed and the whole procedure starts all over again. 

FIGURE 7.1 Schematic presentation of a pill-box optical cell for measurements on solutions at high hydrostatic pressures. The slot and hole allow the pill-box cell to be filled and extra liquid to be released on closing the cell. 

If minute quantities of electricity are to be measured the electrolytic gas coulometer is recommended in this case a 15 per cent solution of sodium hydroxide is used as electrolyte while the electrodes are of platinum or nickel. Both the hydrogen and the oxygen escaping from the closed electrolytic cell... 

A coaxial probe can also be used to measure the through-plane conductivity of membranes. Figure 5.15 shows the schematic for a coaxial conductivity measurement cell. In this method, the membrane is cut to the same size as the inner conductor, and the measured resistance is the through-plane resistance. The resulting conductivity, 2.4 x 10 2 S/cm, is close to that reported in the literature. 

This equation shows the maximal P/O ratio measurable in mitochondria at a zero phosphate potential. Equation (11.97) also indicates that at level flow, the flow ratio does not yield the phenomenological stoichiometry Z but approaches this value within a factor of q. Therefore, if the degree of coupling q is known, it is then possible to calculate Z from the P/O measurements in a closed-circuited cell. 

A vessel made of sintered glass can also be used as a measuring cell [34, 35], In it the equilibrium pressure in Plateau borders is quickly reached and the effect of vessel walls on foam behaviour is omitted. This cell is most efficient in the study of structured foams obtained from protein and saponin solutions. Because of their rheological peculiarities such foams can decay close to the filter and detach from it if the measuring cell has a porous plate only at the bottom of the vessel. 

In the method developed by Exerowa, Cohen and Nikolova [144] the insoluble (or slightly soluble) monolayers are obtained by adsorption from the gas phase. A special device (Fig. 2.28) was constructed for the purpose a ring a in the measuring cell of Scheludko and Exerowa for formation of microscopic foam films at constant capillary pressure (see Section 2.1.2.). The insoluble (or slightly soluble) substance from reversoir b is placed in this ring. Conditions for the adsorption of the surfactant on either surface of the bi-concave drop are created in the closed space of the measuring cell. The surfactant used was n-decanol which at temperatures lower than 10°C forms a condensed monolayer. Thus, it is possible to obtain common thin as well as black foam films. The results from these studies can be seen in Section 3.4.3.3. 

There is another possibility to obtain NBF from insoluble monolayer produced during adsorption from a gas phase. This has been realized in the microscopic foam films from decyl alcohol being adsorbed from a gas phase [394,395]. They were obtained in the measuring cell described in Section 2.3.2. An especially constructed device permits saturation of the closed environment of the cell with vapors of the poorly soluble dodecyl alcohol. The dependence of... 

The foam is produced in a foam generator. After filling cup 2 with the foam the measuring cell is closed with lid 5 so that the porous plate is in contact with the foam. The foam electrical resistance is measured with platinum electrodes connected to a conductivity meter. 

Fig. 7.15 shows foam films formed in the measuring cell of Scheludko-Exerowa (variant A), in a porous plate cell (variant C) (see Section 2.1.2) and a foam. If the radii of the foam films in the measuring cells and the dispersity of the foam (respectively, the radii of the films in the foam) are properly chosen, as well as the applied capillary pressure in the films (variant B) and in the foam liquid phase, the experimental conditions with single foam films and foam films in the foam can be very close. 

Figure 3.52 Flow velocity measured at different heights in closed flow cell of Figure 3.50. Below 170 fua liquid flows to the right in the direction of wave propagation. Above that height liquid flows to the left due to recirculation in the closed cell. (Reprinted with per-mission. See Ref. [75]. 1994 IEEE.)...

Cole has also developed a modification of the Burnett technique, involving three measuring cells with matched volumes and shown schematically in Figure 1(b). Initially all three cells are filled with gas, the valves closed, and is measured. Cell A is then evacuated, the gas from B and C allowed to expand into A, and another measurement of e, made. The procedure is repeated cyclically, evacuating cells B, C, A, B, C in turn. The values of/before and after a complete cycle of expansions are related by... 

This survey deals with the fundamental morphological parameters of foamed polymers including size, shape and number of cells, closeness of cells, cellular structure anisotropy, cell size distribution, surface area etc. The methods of measurement and calculation of these parameters are discussed. Attempts are made to evaluate the effect and the contribution of each of these parameters to the main physical properties of foamed polymers namely apparent density, strength and thermoconductivity. The cellular structure of foamed polymers is considered as a particular case of porous statistical systems. Future trends and tasks in the study of the morphology and cellular structure-properties relations are discussed. 

Voltammetric and coulometric measurements were conducted with the Pt electrode in the nonaqueous electrolyte saturated with CO2 (purity 99.99 %). The electrolyses were carried out in a closed electrolytic cell with CO2 saturated solution for 60 minutes. The current density was -5 mA/cm. The products were analyzed by gas chromatographs and a... 

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