1965 Volume 38 Issue 10 Pages 1792-1794
Ethyl acetate has been employed as a solvent for extracting thallium(III) from its hydrochloric acid solutions. The empirical formula of the extracted metal entity has been found to be HTCl4. Optimum conditions for the extraction of the metal have been determined, and the effect of various factors, e.g., metal concentration, salting-out agents, and the dilution of the solvent, have been investigated. It has been possible to separate thallium(III) from aluminum(III), gallium(III) and indium-(III) by performing a batch-by-batch extraction at a 1.0 N hydrochloric acid concentration.
1) The extracted species is an acid with an approximate formula of HTICl4, the distribution of the species between the two phases depends upon the concentration of the hydrochloric acid present in the system.
2) The extracted species is ionic and may associate in the organic phase to from ion pairs, ion triplets and higher clusters. This is evident from the fact that an increase in the metal concentration causes an increase in the distribution coefficient.
3) There is no primary solvation of thallium, which is tetrahedrally surrounded by chloride ions and which is apparently saturated. This is supported by the observation that the metal could not be extracted from its solution in perchloric acid.
4) The proton of the chlorothallic acid may be solvated (and possibly hydrated, too) in the organic phase, the solvation number being indefinite.
5) Ion pairing results in the formation of an extractable complex and a general mechanism of the type:
may be expected, where S is either H2O or ethyl acetate.
The above equation may well represent qualitatively various reactions at different relative water and ethyl acetate activities.
In general, the system is a simple ion-association extraction system and is quite similar to the extraction of iron(III) and gallium(III) chloride with oxygenated solvents.
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