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A filler-rod technique for controlling redox conditions in cold-seal pressure vessels

William Matthews, Robert L. Linnen and Qiang Guo
A filler-rod technique for controlling redox conditions in cold-seal pressure vessels
American Mineralogist (April 2003) 88 (4): 701-707

Abstract

A new method has been developed to impose different redox conditions in high-temperature-pressure experiments in cold-seal pressure vessels, at 800 degrees C and 2000 bars. Experiments were conducted by loading a metallic filler rod into the autoclave together with H (sub 2) sensor capsules, and pressuring the autoclave with H (sub 2) O. Rod materials tested successfully were Co, Ti, and C (graphite). The oxidation of these rods produces H (sub 2) , but because of diffusive H (sub 2) . However, f (sub H2) quickly reaches a steady state value, and because f (sub H2) is easily measured by the hydrogen sensor method, the effect of the filler rods on the intrinsic f (sub O2) of the autoclave can be quantified. In order to produce oxidized conditions, Ar was used as the pressure medium and metal oxides, contained in Al (sub 2) O (sub 3) tubes, were employed. By using either Ar or H (sub 2) O as a pressure medium, a log f (sub O2) range of NNO -3.9 to NNO +4.6 can be imposed by this method, where NNO is the log f (sub O2) value of the Ni-NiO buffer. The ability to conduct long-run-duration experiments at high temperature and high f (sub H2) conditions is not possible with the traditional double-capsule technique because the buffer assemblage is consumed too quickly. However, run durations of up to 4 weeks with constant f (sub H2) at reduced conditions have been conducted using the filler-rod technique. This technique has been shown to be an effective method in controlling redox conditions in cold-seal autoclaves, and thus can be applied to investigating redox-dependent reactions in a wide range of geochemical systems.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 88
Serial Issue: 4
Title: A filler-rod technique for controlling redox conditions in cold-seal pressure vessels
Affiliation: University of Waterloo, Department of Earth Sciences, Waterloo, ON, Canada
Pages: 701-707
Published: 200304
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 17
Accession Number: 2003-053385
Categories: General geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200317
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