The infrared spectra of cobalt acetate dihydrate provide a direct evidence for the existence of quite strong hydrogen bonds formed by the water protons. An intense band is, namely, found around 2750 cm −1, several additional bands are present at lower frequencies and bands originating from water librations appear above 1000 cm −1. The existence of a band around 3310 cm −1 on the other hand, indicates that much weaker hydrogen bonds are also present. On deuteration the protons involved in stronger hydrogen bonds are apparently replaced by deuterons to a higher degree than those forming weaker H-bonds.