Oscillometry

Abstract The physical and experimental technique of gas adsorption measurements by slow oscillations of a rotational pendulum or, hkewise, the relaxational motion of a freely floating rotator are described. Combinations of the pendulum with either gravimetric or volumetric measurements are outhned. These especially are suited to measure the absorption or solubility of gases in non-rigid or swelling sorbent materials like polymers. Pros and cons of these methods are discussed in brief. List of symbols. References. 

The inertia of mass against acceleration provides another possibility to measure it, i. e. to compare it with a standardized sample mass. Fot practical measurements periodic motions, i. e. oscillations at high or low frequencies in linear or circular modes are used, cp. Ref. [3.1]. For gas adsorption measurements it always should be taken into account that 

For these reasons we will be here restricted to consider only the slow rotational oscillations of sorbent masses in a sorptive gas atmosphere such that the masses moved geometrically are transformed into themselves and only initiate flows in the surrounding gas which are rotationally synunetric. 

Tcxiay this method is used in practice to determine the mass of astronauts in zero gravity (g = 0) conditions like in Spacelab . The astronaut is put on a sledge connected to a hnear spring of known constant (k) and the frequency (m = 2 Ji / T) or the time period of oscillations (T) is measured. Then the astronaut s mass (m) can be calculated as m = k / (o this quantity being an important indicator ofhis health status [5.9]. 

Hence the respective flow fields can be exactly calculated from the Navier Stokes equations, at least for low frequencies, i. e. laminar flows. This is not the case for linear oscillations at either low frequencies, i. e. the linear spring in gas system [3.1], or high frequencies, namely piezo-quartz systems bearing sorbent samples [5.10] or oscillating rod systems (SETARAM). Also at high frequencies the state of the sorbate phase may become transient , i. e. deviate considerably from a thermodynamic equilibrium state. 

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E Pungor, Oscillometry and Conductometry, Pergamon Press, Oxford, 1965... 

Oscillometry 527 as analytical tool, 528 titrations (H.F.), 527 Osmium tetroxide catalyst 381 Ostwald s dilution law 31 Ovens electric, 97 microwave, 97 Overpotential 506 Overvoltage see Overpotential Oxalates, D. of as calcium carbonate via oxalate, (g) 484... 

The introduction of a pure inductance L becomes necessary in a resonance procedure (see oscillometry below). 

In the latter procedure, which is often called oscillometry6, one observes the frequency at which resonance occurs or one retunes the oscillator to the original frequency, e.g., with the aid of a calibrated capacitor parallel to the sample cell. Further, in oscillometry it is useful to compare in parallel with a reference frequency unit. 

Electrical conductivity/electrical resistivity Dielectric constant and loss factor Oscillometry Gaseous conduction... 

Pungor, E. Oscillometry and Conductometry. The Intern. Ser. of Monographs on Analytical Chemistry, Vol. 21. Oxford Pergamon Press 1965. 

Cells for Conductimetry. Reliable and precise measurements of electrolytic conductance require attention to the design of cells, electrodes, and measuring circuitry. Extraction of an ohmic resistance from AC bridge measurements is not a trivial task, particularly in solutions with high resistance (such as organic solvents) or low resistance (molten salts). Expositions of the principles are provided in monographs that emphasize aqueous solution,54,55 and in a review of conductimetry and high-frequency oscillometry that emphasizes analytical applications.56... 

Refs. [i] Pungor E (1965) Oscillometry and conductometry. Pergamon Press, New York [ii] Sugimachi M, Okamoto H, Hoka S, Sunagawa K (2004) Blood Press Monit 9 135... 

Loveland JW (1963) Conductometry and Oscillometry. In KolthofFiM, Living PJ and Sandell LB, eds. Treatise on analytical chemistry. Part I (Theory and practice), Vol 4, section D-2, Electrical methods of analysis (Reilley CN, section advisor), pp. 2569-2630. John Wiley Sons, New York. 

Ohm s law applies to both metallic conductors and electrolyte solutions. However, anomalies occur under special conditions such as high voltages or very high frequencies. Our emphasis will be to explore electrolytic conductance for analytical uses under the more ideal conditions of low volta (1 to 100 V) and low frequencies (0 to 5000 Hz). We will also introduce the technique of oscillometry, which is an... 

Oscillometry differs from conductometry in several respects. 

In conductance, the ions absorb energy which is translated into heat and motion. In oscillometry, we have not only this aspect, but also the capacitance effect in which molecules absorb and return energy each frequency cycle owing to the induced polarization and alignment of electrically unsymmetrical molecules. 

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