A method is described for determining trace amounts of thallium in nickel-based alloys by electrothermal atomic absorption spectrometry (ETAAS). The alloy was dissolved by two methods, one a microwave digestion procedure and the other a hot-plate dissolution method. Different acids were used for each of the two different methods. For microwave digestion, a combination of H2S04, HNO, and HF acid was used, whereas for hot-plate dissolution, a combination of H, SO, , HF and H202 was used. Ascorbic acid (C6H&@6) was used as chemical modifier. Comparable results for TI are achieved by the two methods of dissolution. The installation of a stabilized temperature platform in the graphite furnace tube improves the absorbance signal and the precision of the measurement. The detection limit was 0.1 ng ml-' of TI ( 3 ~~) .The accuracy of the method was elucidated through the analysis of certified nickel-based alloys.

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A complexometric method for the determination of copper(l1) in the presence of other metal ions is described. The method is based on the selective complexing ability of mercaptosuccinic acid towards Cu(ll). Copper, present in a given sample solution, is initially complexed by the addition of EDTA solution and the excess is titrated against zinc solution. A known excess of mercaptosuccinic acid is then added to release EDTA from the Cu(ll) -EDTA complex, which is subsequently titrated against zinc solution. The amount of EDTA replaced from the complex is equivalent to the amount of Cu(ll) in the solution. Various metal ions such as Pb(ll), Ni(ll), Co(ll), Cd(ll), Fe(lll), AI(III), Ti(IV), Th(lV) and rare earths and anions such as CI-, N03-, S042-, acetate, tartrate and Fwere found not to interfere. Interference from ions such as Sn(lV), Zr(lV), Bi(lll), Hg(ll) and Pd(ll) can be overcome by the use of suitable masking agents. The method has been successfully applied to the analysis of various alloys and ores.

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