Abstract
The state of water in inorganic crystal hydrates has been discussed, and the various distortions of the water molecule, as far as its dissociation, under the influence of the environment have been analysed. The reactions involved in the extensive dehydration of crystal hydrates have been examined from the viewpoint of the relationship between the state of water in the hydrate and the characteristic features of the dehydration processes leading to irreversible changes in the substance undergoing dehydration and to the decomposition of a complex oxo-anion. The bibliography contains 221 references.