Molecular diffusion of CF₃SF₅ in pure water and artificial seawater

Authors

Jonathan Vardner
Brice Loose, University of Rhode IslandFollow

Document Type

Article

Date of Original Version

2016

Department

Oceanography

Abstract

We have experimentally determined the diffusion coefficient for trifluoromethyl sulfur pentafluoride (CF₃SF₅) in pure water and artificial seawater over a temperature range of − 2.0 °C to 30.0 °C. A working gas standard containing known concentrations of CF₃SF₅ and sulfur hexafluoride (SF₆) was prepared. The working standard was allowed to diffuse across a water barrier, stabilized with agar gel, and the diffused gas was swept into a gas chromatograph with an electron-capture detector to measure the resulting gas mixing ratio. The mixing ratios for both CF₃SF₅ and SF₆ were measured to determine the diffusivity for each species. The diffusion coefficient for SF₆ was determined during these experiments as a check against existing literature values and to validate our experimental setup. The experimental data were fit to the Arrhenius equation to yield the following equations D_CF3SF5 = 0.0015 exp (-12.9/RT) and D_SF6 = 0.037 exp (-19.8/RT), where R is the gas constant in units of kilojoules per mole per kelvin and T is the temperature in kelvin. At the mean temperature of the ocean, 18 °C, D_CF3SF5 = 7.02 × 10^-6 ± 9.9% and D_SF6 = 1.03 × 10^-5 ± 13.8 % cm²/s. The diffusion coefficients for SF₆ matched the literature data within 4.3% for all temperatures.

Citation/Publisher Attribution

Vardner, J., & Loose, B. (2016). Molecular diffusion of CF₃SF₅ in pure water and artificial seawater. Marine Chemistry, 180, 51-56. doi: 10.1016/j.marchem.2016.01.005

Available at: https://doi.org/10.1016/j.marchem.2016.01.005

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.