High-temperature indium(III) solutions

The speciation of metal ions in high-temperature, high-pressure aqueous solutions is important in geochemical and environmental processes, such as metal transport and ore formation. Changes in the fundamental properties of water with temperature will affect the number and type of ligands around the metal and the degree of ion pair formation. X-ray absorption spectroscopy allows these changes to be monitored. We have investigated the solvation and stepwise complex formation of In(III) in aqueous solutions up to 350 C. In solutions containing perchlorate and nitrate ions there was no change in the In-O bond length (2.13 Angstrom), and no ion pairing with nitrate ions. In chloride solutions both O and Cl are present in the inner coordination sphere, with the proportion of Cl increasing with increasing temperature and Cl molality.