Determination of antimony in galena by atomic-absorption spectrometry

Abstract

In the determmatlon ofantimony m galena, hydrochlortc acid cannot be used to dissolve the sample because the chlorrde of antimony(III), as well as those of Ge( IV), As( I II), Sn( IV) and Hg( II), are volatile at boiling temperatures’. If concentrated mtrtc acid is used, lead sulphate precipitates, and Sb, BI, Ag, Cu, Ca and Sr are parttally coprectprtated i However, the lead sulphate can be easily drssolved m strong hydrochlorrc acid solution, 11 was found that no precipttate was formed even when the solution was diluted to 5% m hydrochlortc acid; the solution remamed clear on storage and when dilute sulphuric acid was added to an aliquot, no prectpttate was formed Accordingly, the galena could be dissolved with concentrated mtric acid, and then a hydrochloric acid solution of the sample at any desired acidtty could be prepared Smce some sulphide-forming elements (Sb, Br, Ag) remam m solution only in strong hydrochloric acid, the extraction of antimony with methyl isobutyl ketone (MIBK) irom such solutions was exammed. An extraction procedure would not only concentrate the antimony, but would also mmtmize Interferences, especially that of lead Lead has been reported’ to interfere m the determinatton of antimony by atomtc-absorption spectrometry at 217.6 nm; Slavm and Sattur3 suggested that antimony m the presence of lead should be determined at the resonance lmes 206 83 or 231.15 nm. Antimony m lead has been determined by a spectrophotometric method4 in which the antimony IS extracted mto di-isopropyl ether from hydrochloric acid solutton before tts spectrophotometric determination with iodide. Meranger and Somers’ determmed antimony m titanium dioxide by atomic-absorptton spectrometry after tts extractton into MIBK from 10-14°/0 (w/v) hydrochloric acid solution. Goto er ~1.~ reported that antrmony(II1) and (V) are quantttattvely extracted from hydrochlortc acid solution less than 8 h4, but that m the presence of 5 M sulphuric acid, they can be completely extracted from 0 5 M hydrochloric acid solution In the method proposed here, galena is dissolved m concentrated mtrtc actd, after removal of the excess, lead sulphate acid, and the antimony IS extracted into absorbance at 217.6 nm.