Oxygen Isotopic Exchange Between CO2 and Phosphoric Acid: Implications for the Measurement of Clumped Isotopes in Carbonates

Peter K. Swart, Sean T. Murray, Philip T. Staudigel, David A. Hodell

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Experiments have been conducted in which CO2 gases with varying C and O isotopic compositions and with stochastic and nonstochastic Δ47 values have been allowed to equilibrate with phosphoric acid of two concentrations in reaction vessels of varying dimensions at temperatures of 25 and 90 °C. Rates of 13C18O and 18O exchange between the CO2 and the phosphoric acid varied as a function of the length of exposure, volume of reaction vessel, acid strength, and difference of the initial Δ47 and δ18O values of the CO2 from theoretical equilibrium values. The Δ47 values were also altered by heated stainless steel surfaces such as those found within the Kiel device and other preparation systems. These results have been used to explain variations in the differences in the fractionation between 25 and 90 °C reported for calcite by different workers as well as differences in the slopes between temperature and Δ47 values produced by reacting samples at different temperatures (25 and 90 °C).

Original languageEnglish (US)
Pages (from-to)3730-3750
Number of pages21
JournalGeochemistry, Geophysics, Geosystems
Issue number7
StatePublished - 2019


  • CO
  • clumped isotopes
  • phosphoric acid

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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