The Structure of Chlorine Hydrate

In 1811 Humphry Davy [1] showed that water is a component of the phase that had earlier been thought to be solidified chlorine, and twelve years later Michael Faraday [2] reported an analysis that corresponds to the formula Cl2•10H2O. He surmised that his determination of the chlorine content was low, and later studies have indicated the composition to be close to Cl2•8H2O. Since Faraday's time similar crystalline hydrates of many gases with small molecular volume, including the noble gases and simple hydrocarbons, have been reported. The determination of the structure of ice and the development of an understanding of the nature of the hydrogen bond have strongly suggested that these substances are clathrate compounds, with a tetrahedral hydrogen-bonded framework of water molecules (with O-H•••O = 2.76 Å, as in ice) defining cavities large enough to contain the other molecules.