Hydrates host water cages

It should be noted that the use of the KVSj charts implies that both the gas phase and the hydrate phase can be represented as ideal solutions. This means that the Kvsi of a given component is independent of the other components present, with no interaction between molecules. While the ideal solution model is approximately acceptable for hydrocarbons in the hydrate phase (perhaps because of a shielding effect by the host water cages), the ideal solution assumption is not accurate for a dense gas phase. Mann et al. (1989) indicated that gas gravity may be a viable way of including gas nonidealities as a composition variable. 

Clathrate hydrates are crystalline inclusion compounds composed of host water cages that trap guest molecule-. [-.The three most common types of clathrate hydrates are known as structure I, II, and H, which differ in the type of water cage they contain. The type of clathrate hydrate structure formed depends mainly on the size of the guest molecules present (for further details, see the article Clathrate Hydrates and Refs. [8,9]). The structures of these compounds were first determined from x-ray diffraction studieshowever, as mentioned previously, vibrational spectroscopy can provide important complementary information on the structures and dynamics of these compounds and can also detect the presence of any guest molecule-host lattice interactions. 

Gas hydrates are non-stoichiometric crystals formed by the enclosure of molecules like methane, carbon dioxide and hydrogen sulfide inside cages formed by hydrogen-bonded water molecules. There are more than 100 compounds (guests) that can combine with water (host) and form hydrates. Formation of gas hydrates is a problem in oil and gas operations because it causes plugging of the pipelines and other facilities. On the other hand natural methane hydrate exists in vast quantities in the earth s crust and is regarded as a future energy resource. 

Depending on conditions, frozen substances in comet nuclei can be crystalline ices, amorphous ices, and clathrate hydrates (compounds in which cages in the water-ice lattice can host guest molecules). Compositions of the ices and associated organic materials in comets have been determined from both telescopic and spacecraft observations. Spectral line measurements of gases in a comet s coma allow the identification of molecules and radicals. An inherent difficulty in spectral measurements is that volatiles in the coma are commonly broken... 

In a gas hydrate, water forms a hydrogen-bonded cage and different molecules reside inside the cage. Water is called the "host,"... 

Clathrate hydrates (known also as gas hydrates) belong to a large class of crystalline, non-stoichiometric, inclusion-compound materials that are stable within a certain range of pressure and temperature. The host solid framework structure is made up of water molecules, connected through hydrogen bonds that form cavities (cages) . The cavities can be stabilized by the inclusion of small molecules such as CH4, CaHg, CO2, N2, Ar, etc. Over 100 different molecules are known to form hydrates. 

Until 1962 only physical inclusion compounds were known. Argon, krypton, and xenon form cage or clathrate compounds with water (clathrate hydrates) and with some organics such as quinol. The host molecules are arranged in such a way that they form cavities that can physically trap the noble gas atoms, referred to as guests. The noble gas will be released upon dissolution or melting of the host lattice. 

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