4F - S04 - Combustion Infrared Detection

A 0.2g sample is combusted in a resistance furnance at 550^°C in a pure oxygen environment. During combustion, sulphur-bearing elements are reduced, releasing sulphur, which binds with oxygen to form SO₂. Sulphur is measured as a sulphur dioxide in the infrared cell. An Eltra CS-2000 used for analysis.

As described in ASTM E1915 sulphate sulpur, in the absence of sulphide forms of sulphur, the total sulphur may be used to estimate the concentration of sulphate sulphur. The pyrolysis residual sulphur may be the best estimate of sulphate sulphur in the presence of barite, alunite, jarosite, since these sulphate forms are not dissolved by sodium carbonate and in the presence of orpiment and realgar, since these sulphide minerals are soluble in sodium carbonate.  The sodium carbonate sulphur loss may be the best estimate of sulphate sulphur in the presence of metal sulphide minerals other than iron, which may not be lost by pyrolysis and the absence of barite, alunite, jarosite, orpiment and realgar.