Oxygen fugacities, measurements

Brett R., Huebner J. S., and Sato M. (1977) Measured oxygen fugacities of the Angra dos Reis achondrite as a function of temperature. Earth Planet. Sci. Lett. 35, 363-368. 

Mendybaev R. A., Beckett J. R., Stolper E., and Grossman L. (1998) Measurement of oxygen fugacities under reducing conditions non-Nemstian behavior of Y203-doped zirconia oxygen sensors. Geochim. Cosmochim. Acta 62, 3131-3139. 

Williams, Richard J. Mullins, 0. "A System Using Solid Ceramic Oxygen Electrolyte Cells to Measure Oxygen Fugacities in Gas-Mixing Systems" Technical Memorandum TMX-58167,... 

The measurement of diffusion rates as functions of various activities, in particular oxygen fugacity, is extremely important to clarifying the diffusion mechanisms and aid in extrapolation. The work of Ryerson et al. (1989) is the only geochemical example of such type of work. Questions of concern include under what conditions does the /02-dependence occur, and what does it tell us about the main mechanism of O2 transport (e.g. permeation versus diffusion, network versus molecular oxygen diffusion etc.). 

Delaney JS, Sutton SR, Newville M, Jones JH, Hanson B, Dyar MD, Schreiber H (2000) Synchrotron micro-XANES measurements of vanadium oxidation state in glasses as a function of oxygen fugacity Experimental calibration of data relevant to partition coefficient determination. Lunar Planet Sci... 

When it comes to physical meaning, parameters in the thermodynamic model sometimes have meanings that are difficult to relate to the real world, as we have seen, particularly in the case of standard states. The example most relevant here is oxygen fugacity, another measure of the state of oxidation of systems, which we will consider in a later section. Oxygen fugacity is often used as a parameter in systems which contain no O2, just as water contains no free electrons. Still, there are other. systems where fugacity approximates partial pressures, and this is a link to reality that... 

Fig. 18.6. Experimental control and measurement of hydrogen fugacity. (a) Schematic arrangement of an oxygen-buffered experiment, (b) Shaw membrane for external control of hydrogen fugacity. Apparatus can also be used as a hydrogen sensor to measure H2 pressure externally, (c) Double capsule method of controlling both oxygen fugacity and HCl activity within an inner, Pt capsule.

It is also possible to measure oxygen and other gas fugacities with electrochemical sensors. These methods use the same theoretical principles that apply to measurement of Eh. The design and operation of such sensors is described in detail by Sato (1971) and Huebner (1987). We will illustrate the technique briefly, by describing an oxygen fugacity sensor. 

Electrochemical Cell for Measuring Oxygen Fugacities in Oxidic Glass-... 

Main electrochemical cell arrangements for measuring oxygen fugacities of oxidic glassforming melts (a) separated reference and measuring electrodes (b) single-rod electrode . 

Figure 26-IQ. Time dependence of temperature-dependent emfs of the cell Pt/melt/Pt,M with M = 1% Ir (a), 5% Rh (b), and 10% Rh (c), showing irreversible behavior of the alloys and demonstrating that only pure platinum can be used for constructing measuring electrodes of oxygen fugacity cells. dT/dt = —300 K/h.

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