On the pH-dependent formation constants of iron(III)-sulfur(IV) transient complexes |
| |
| Authors: | Eric A Betterton |
| |
| Institution: | (1) Department of Atmospheric Sciences, University of Arizona, 85721 Tucson, AZ, USA |
| |
| Abstract: | An experimental study is described of Fe(III)-S(IV) formation constants measured as a function of pH (1–3), ionic strength (0.2–0.5 M) and Fe(III)]
T
(2.5–5.0×10–4 M) using a continuous-flow spectrophotometric technique to make observations 160 ms after mixing. Preliminary experiments using pulse-accelerated-flow (PAF) spectrophotometry to measure rate constants on a microsecond timescale are also described. The conditional formation constant at 25 °C can be modeled with the following equation: {ie307-1} where {ie307-2}K
7 andK
8 can be interpreted as intrinsic constants for the coordination of HSO
3
–
by FeOH2+ and Fe3+, respectively, but until further evidence is obtained they should be regarded as fitting constants. PAF spectrophotometry showed that the initial reaction of Fe(III) with S(IV) (pH 2.0) is characterized by a second-order rate constant of  4×106 M–1 s–1 which is comparable to rate of reaction of FeOH2+ with SO
4
2–
. However, the PAF results should be regarded as preliminary since unexpected features in the initial data indicate that the reaction may be more complex than expected. |
| |
| Keywords: | Sulfur dioxide iron(III)-S(IV) complexes sulfur(IV) autoxidation pulsed-accelerated-flow spectrophotometry |
| 本文献已被 SpringerLink 等数据库收录！ |
|
