Clathrate compound

Clathrates (Latin clatratus barred, '; German also partially clathrates ) are inclusion compounds of two substances, one of which a guest molecule is embedded in a lattice or cage of a host molecule. They are called also Käfigeinschlußverbindungen. For the lighter noble gases, helium and neon, they are the only known compounds.

Inclusion of gaseous substances in water are also called gas hydrates. In clathrates with water, the molar ratio of gas / water usually 8/48, with large einzulagernden gas particles and discounts for 6 / 48th Methane hydrate is formed in cold seas in great depth from natural sources of methane. It is at temperatures that are only slightly above 0 ° C, stable.

In large glaciers (eg at the South Pole ), air ( from the glacier forming snow) gradually installed at a depth of some 100 meters below the pressure prevailing there as clathrate in the ice.

In addition to water can also form clathrates some organic compounds, such as hydroquinone with argon forms an inclusion compound in a 3:1 ratio. In organic compounds can also be more reactive gases such as hydrogen halides or hydrogen sulfide store.

A distinction must be clathrates of interstitial solid solutions of compounds of metals with non-metals as well as of complex compounds which true chemical compounds.

Technical application

Clathrates are utilized industrially in the urea - extractive crystallization. This is used for the selective separation of n- paraffins from iso- paraffin, aromatic, naphthenic, and n- paraffin mixtures (kerosene ). The urea forms during crystallization channels with a diameter of 0.53 nanometer. Only n- paraffins can penetrate these small channels and be bound there. At 75 ° C, the urea crystal dissolves in water again, and the n-paraffins are released.