title: A methodology for the determination of reductive sulphur in optical and technical glass.
abstract: This paper describes an analytical method for the determination of reductive sulphur (S(IV), S(-II)) in glass. The glass sample is dissolved in hydrofluoric/hydrochloric acid mixture and the sulphur is separated via distillation in an apparatus made of polyfluoralkoxyethylene (PFA). The distilled hydrogen sulphide is trapped in buffered boric acid-zinc acetate solution and subsequently determined after conversion to an ethylene blue dye. The range of the method lies within a range of 2-1200mugg(-1) reductive sulphur. The quantification limit for reductive sulphur is 2mugg(-1). Different analysed glass types show either no detectable reductive sulphur or up to 30% of the total sulphur content reductive sulphur. The inter-laboratory standard deviation shown by a round robin test performed is excellent (+/-4mugg(-1); average 59mugg(-1)). Sources of error of the methodology are discussed.
authors.affiliation: SCHOTT GLAS, Chemical Analysis, Hattenbergerstrasse 10, Mainz 55014, Germany.
authors.forename: Udo
authors.initials: U
authors.lastname: Rohr
authors.forename: Lothar
authors.initials: L
authors.lastname: Meckea
authors.forename: Christine
authors.initials: C
authors.lastname: Strubel