Sulphide sulphur is calculated from the difference between measurements at 550oC and 1450oC using combustion/IR, pyrolysis loss sulphur as described in ASTM E1915. An interpretation of the calculated sulphide value must be made in reference to the mineralogy of the sample.
According to ASTM E1915 in regards to sulphide sulphur, “In the absence of sulphate forms of sulphur, total sulphur may be used to estimate the sulphide sulphur concentration. The pyrolysis loss sulphur may be the best estimate of sulphide sulphur, particularly where the acid generation potential due to iron sulphides is desired. The nitric acid loss method may be appropriate where the sulphide forms are primarily pyrite and marcasite and pyrrhotite is absent, since pyrrhotite may react with acid. The sodium carbonate residual sulphur method is most appropriate where the concentrations of metal sulphide minerals in addition to iron are desired in the absence of barite, alunite, jarosites, orpiment and realgar.”
Sulphide S = Total S – Measured SO4