The inorganic ion exchanger chromium(ll1) hexacyanoferrate(ll1) has been found to be specifically selective for silver ions, with a sorption capacity of ca. 10 mequiv. 9-1 of the exchanger. Sorption of the silver i o n s f r o m acidic ( I 0 m o l dm-3 HN03) and salt solutions (8 m o l dm-3 NH4N03), containing different levels of silver nitrate, has been studied. The studies, which were aimed a t using the exchanger for the recovery of silver ions from the waste, generated from chemical oxygen demand determinations, showed ca. 80-95% recovery of silver ions f r o m concentrated waste. The exchanger also selectively removed silver ions from simulated waste containing Bi, Ca, Cd, Co, Cull, Mg, Mn, Ni, Pb and Zn ions.

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A new eluent has been developed for the suppressed ion chromatographic separation of strontium from large amounts of calcium. Together with a Dionex CS-2 separator column, the eluent, a mixture of 2.5 mmol dm-3 ethylenediamine, 5 mmol dm-3 hydrochloric acid and 1 mmol dm-3 Zn2+, was successfully used for the simultaneous determination of strontium, magnesium and calcium in high salinity sub-surface waters. The results of the determination of magnesium, calcium and strontium in sub-surface Arab-D brine and its mixtures with aquifer Wasia and sea-water compare well ( p > 0.1) with those obtained by a standard atomic absorption spectrometric method. A base line separation of magnesium, calcium and strontium from each other and from a large excess of sodium in a sub-surface brine can be achieved in approximately 8.0 min. This is a considerably shorter time than that required to achieve a reasonably good separation factor between calcium and strontium by other liquid chromatographic methods, although such methods have not been used for the determination of alkaline earth metal cations in sub-surface waters.

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