Hydration of ions in aqueous solution studied by IR spectroscopy

A method has been developed by which it is possible to obtain information about the hydration shell around molecules and ions in aqueous solutions. Two characteristics of the method are: 1) The OD stretchings of isotopically diluted HDO molecules are studied by IR spectroscopy. 2) Differences between spectra are taken to remove the contribution from the bulk water. Results are given for some metal perchlorates and chlorides. It is shown that each type of dissolved ion gives a certain wavenumber for an OD stretching band. Earlier results from the solid state are used to derive O…O distances which correspond to those wavenumbers.