Enclosure compounds

Atwood JL, Atwood JD (1976) Non-stoichiometric liquid enclosure compounds ( Liquid Clathrates ) In King B (ed) Inorganic compounds with unusual properties. American Chemical Society, Washintgton, 112-127... 

Non-Stoichiometric Liquid Enclosure Compounds ( Liquid Clathrates )... 

The liquid complexes have many of the properties ascribed to enclosure compounds, and the term liquid clathrate seems to be an appropriate designation. 

The discovery of buckminsterfullerene led to a considerable amount of research into its properties and compounds. Particular interest has been shown in trapping metal ions inside the carbon cage to form enclosure compounds. Buckminsterfullerene itself is often simply called fullerene. The term also applies to derivatives of buckminsterfullerene and to simi-... 

Atwood. J.L. Atwood. J.D. Non-Stoichiometric Liquid Enclosure Compounds ("Liquid Clathrates"). In Inorganic Compounds with Unusual Properties King. R.B., Ed American Chemical Society Washington, 1976 112-127... 

Various fullerene derivatives ate known in which organic groups ate attached to carbon atoms on the sphere. In addition, it is possible to produce novel enclosure compounds by trapping metal ions within the cage. 

In the final step of the analysis, the iodine is titrated with thiosulphate. The iodine is reduced to iodide, and the thiosulphate in turn is oxidized to the tetrathionate ion. The concentration of the thiosulphate solution used for the titration must be known precisely. The endpoint of the redox titration is commonly indicated by a starch indicator or by photometric or amperometric endpoint detection. The starch indicator forms an enclosure compound with iodine. The large electron cloud of the iodine interacts with the hydroxo dipoles in the starch helix resulting in an intensely blue colour of the iodine starch complex. Nevertheless, the iodine molecules can leave the starch hehx easily and thus can be reduced by thiosulphate. The endpoint of the titration is clearly marked by the change from blue to colourless. 

Atwood, J.L. and Atwood, J.D., Non-stoichiometric liquid enclosure compounds ( liquid clathrates ), in Inorganic Compounds with Unusual Properties, bl. 150, ed. R.B. King, American Chemical Society, Washington, DC (1976), pp. 112-127 (c)Atwood, J.L., Liquid clathrates, in Recent Developments in Separation Science, bl. 3, ed. N.N. Li, CRC Press, Cleveland (1977), pp. 195-209. 

Fig. 43. Amylose. The molecular shape of amylose explains some of its chemical and biochemical properties. With iodine, amylose turns intensely blue. This venerable reaction has been explained only recently. It was found that iodine molecules enter the hollow center of the coil created by the glucose units. In such enclosure compounds iodine exhibits changed physical characteristics, such as the strong absorption of light. There are enzymes that slit open this tube and free fragments, each of which contains six glucose units (Section 6).

Inclusion compounds open up a wide area of applications (1,2,17—28). An important aspect in this connection is the specific microenvironment created by the host enclosure of the guest which exerts an influence on the physical, spectroscopic, chemical, and other properties of the guest. 

Enclosure also changes the redox properties of a compound, its color, and other physical properties (1,2). On this basis nonlinear optical materials, luminescence markers, controlled light switches, and other high-tech devices might be designed and prepared (15,17,137). 

Partial enclosure with local exhaust ventilation, or local exhaust ventilation, of working position separate hazardous processes from other work, e.g. spray-painting with epoxy-containing sensitizing and carcinogenic compounds. 

To retard corrosion and to facilitate future maintenance (e.g., allow the non-destructive removal of threaded Junction box covers), all threaded connections should be lubricated with an antiseize compound which will not dry out in the environment. If lubricant is applied to the threaded (or flanged) portion of covers of explosion-proof enclosures, the lubricant must have been tested and approved as suitable for flame path use. It is cautioned that some lubricants contain silicone, which will poison most catalytic gas detector sensors and should not be used near gas detectors. 

An example is the complex with argon which can be kept indefinitely in an ordinary bottle, although the equilibrium pressure of argon over the crystal amounts to several atmospheres at room temperature. Powell31 named these complexes "clathrate compounds, which according to him are those compounds "in which two or more components are associated without ordinary chemical union but through complete enclosure of one set of molecules in a suitable structure formed by another. ... 

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. 

Fukui Y, Doskey PV. 1996. An enclosure technique for measuring nonmethane organic compound emissions from grasslands. Journal of Environmental Quality. 25 601-610. 

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