A comparison of iron redox ratios in silicate glasses determined by wet-chemical and ⁵⁷Fe Mössbauer resonant absorption methods

Abstract

The Fe³⁺/Σ Fe of twenty-nine experimentally formed, iron-bearing silicate glasses has been determined by wet-chemical and Mössbauer spectroscopic methods from 5–10 mg individual splits of 20–40 mg experimental run products. The wet-chemical and Mössbauer analyses were conducted in two separate laboratories (University of California, Berkeley, and the Geophysical Laboratory, respectively). The Fe³⁺/Σ Fe ranges from less than 0.2 to 0.96, and the total iron oxide content of the samples, from 2.2 to 34.7 wt %, added as Fe₂O₃. The interlaboratory comparison shows 70% of the Fe³⁺/ΣFe analyses from the two methods within the quoted uncertainties (±1 σ) of each other and 83% of the analyses within ±2 σ of each other. Replicate analyses in the current data set result in variations within ±1 σ. These uncertainties are similar to those obtained from several hundred Fe³⁺/Σ Fe analyses of reequilibrated natural rock and simple system compositions carried out with identical analytical methods in the two laboratories. There is no systematic bias in the results from either of the two techniques. The Fe³⁺/Σ Fe of silicate glasses can be analyzed, therefore, with equal confidence by either the wet-chemical or the Mössbauer spectroscopic method.