Coprecipitation of microgram amounts of lead and tin with aluminium, using 8-hydroxyquinoline, tannic acid and either thionalide or sodium sulphide

Abstract

Sodium sulphide is shown, by atomic-emission spectrometry using a carbon arc, to be more effective than thionalide for the recovery of lead in the range 15–150 µg from acetate-buffered solutions at pH 5.2. When combined with 8-hydroxyquinoline and tannic acid, only 50–70% of the lead is precipitated with thionalide, whereas sodium sulphide provides a complete recovery. Tin is fully recovered with either combination of the three reagents, but it appears that 8-hydroxyquinoline on its own also fully precipitates this element. Calibration graphs derived from mixed-powder standards for lead, tin and iron differed significantly from those obtained with precipitated materials, despite the use of internal standards. This could not be attributed to the downward drift of spectrometer sensitivity noted during the investigation.