Determination of iron monosulfide and iron disulfide in suspensions by an electrochemical method using a platinum-silver twin-electrode.

New electrochemical technique with a Pt-Ag twin electrode is proposed for the determining the contents of iron sulfides (FeS and FeS(2)) in a suspension. After electrolytic oxidation with a Pt electrode, Fe(2+) was measured by linear sweep voltammetry. From relations of the charge amount from the baseline to the peak in the voltammogram of Fe(2+) with the content of FeS or FeS(2), linear calibration curves (a) and (b) were prepared, respectively. After measurements of Fe(2+), Fe(2+) and S(0) were reduced with a Pt electrode to remove Fe(2+) and to produce S(2-). With an Ag electrode, Ag(2)S was deposited on Ag. A linear curve (c) was prepared from a relation between the charge amount of the Ag(2)S peak part and the FeS content. However, in the suspension of FeS(2), Ag(2)S can not be detected. When this method is applied to a mixed suspension of FeS and FeS(2), the content of FeS can be determined with curve (c), whereas curves (a) and (b) were not effective in the mixed suspension.