ABSTRACT

It is definitely shown that the main cause of error encountered in the precision isotope analysis of sulfur is in the isotope exchange reaction between SO₂ and SO₃ during the combustion process of SO₂ preparation. The isotope fractionation factor between the two oxides is estimated to be 1.0035 at 1200°C. From this value, it is predicted that 3% fluctuation in the yield of SO₂ would introduce uncertainty of 0.1‰ in the results of the ratio measurement. An improved combustion technique to maintain a constant yield of SO₂ is described where pure oxygen is replaced by a nitroden-oxygen mixture (15: 1, v/v).