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Ncthcrlandr ' A .RAPID AND ACCURATE DETERMINATION OF TRACE QUANTITIES OF SULPHUR IN TIN
The demands for pure materials of all types are incrcming daily, and tin is no exception. A particularly undesirable contaminant of tin is sulphur. The usual chemical methods for the analysis of very low levels of contamination arc inadequate since the standard deviation is frequently of a similar orclcr of magnitude.
During the past decade a relative-concluctimetric method has been developed for the determination of sulphur in ferrous' and organic" materials, which involves the combustion of the sample in oxygen. The evolved sulphur dioxide is absorbed in a conductivity cell containing acidified hydrogen pcroxidc and the change in conductivity is a measure of the sulphur content of the material. This paper clescribes an extension of th.is technique to handle the low concentrations of sulplrur found in refined tin. ESPERIMENTAL Unglazed porcelain boats (5 cm x I cm x I cm) (H. Wijsthoff O.H.G. Uochum, Germany) ; Wiisthoff Sulmhograph 12, Sulphur Analyser (0-20 p.p.m.) ; Wijsthoff Gas Dosing Device, consisting of a cascade of gas dilution pumps.
Reageti Is
Absorption reagent: 0.5 ml of 30% (w/w) hydrogen peroxide per litre of 0.002 N sulphuric acid (both analytical-reagent-grade).
Microanalytical-reagent-grade sulphanilic acid.
Procedure
Reduce the tin to fine turnings. Wash well with acetone to remove any grease, and dry. Place a porcelain boat in the secondary furnace tube and condition in oxygen at 1350" for IO min. Remove the boat and allow it to cool. Accurately weigh ca. I g of tin and transfer to the boat, distributing the turnings evenly. Fill the conductivity cell and introduce the boat into the combustion tube (1350").