Structure and Composition
The average methane clathrate hydrate composition is 1 mole of methane for every 5.75 moles of water, though this is dependent on how many methane molecules "fit" into the various cage structures of the water lattice. The observed density is around 0.9 g/cm3. One litre of methane clathrate solid would therefore contain, on average, 168 litres of methane gas (at STP).
Methane forms a structure I hydrate with two dodecahedral (12 vertices, thus 12 water molecules) and six tetradecahedral (14 water molecules) water cages per unit cell. This compares with a hydration number of 20 for methane in aqueous solution. A methane clathrate MAS NMR spectrum recorded at 275 K and 3.1 MPa shows a peak for each cage type and a separate peak for gas phase methane. Recently, a clay-methane hydrate intercalate was synthesized in which a methane hydrate complex was introduced at the interlayer of a sodium-rich montmorillonite clay. The upper temperature stability of this phase is similar to that of structure I hydrate.
Read more about this topic: Methane Clathrate
Famous quotes containing the words structure and/or composition:
“Agnosticism is a perfectly respectable and tenable philosophical position; it is not dogmatic and makes no pronouncements about the ultimate truths of the universe. It remains open to evidence and persuasion; lacking faith, it nevertheless does not deride faith. Atheism, on the other hand, is as unyielding and dogmatic about religious belief as true believers are about heathens. It tries to use reason to demolish a structure that is not built upon reason.”
—Sydney J. Harris (1917–1986)
“Those Dutchmen had hardly any imagination or fantasy, but their good taste and their scientific knowledge of composition were enormous.”
—Vincent Van Gogh (1853–1890)