Infra-red spectra of salt hydrates. Correlation between the fundamental symmetric and asymmetric stretching frequencies of the water molecules

Abstract

Fundamental band contours in the 3500 cm^–1 region for various perchlorates, chlorates, bromates and iodates containing water have been measured both for H₂O and HOD. The results show that, for the monohydrates, the water is symmetrically bonded, the frequency for the H—O stretch of HOD being the mean of ν_s and ν_as for H₂O. The results correlate very well with those previously reported for water symmetrically bonded to a range of hydrogen bond acceptors.

Results for various forms of ice appear to deviate markedly from this correlation, as also do those for water in potassium oxalate monohydrate. Reasons for this deviation are proposed, and possible values for ν_as and ν_s in liquid water are considered.