Krypton clathrates

Krypton clathrates have been prepared with hydroquinone and phenol. 85Kr has found recent application in chemical analysis. By imbedding the isotope in various solids, kryptonates are formed. The activity of these kryptonates is sensitive to chemical reactions at the surface. Estimates of the concentration of reactants are therefore made possible. Krypton is used in certain photographic flash lamps for high-speed photography. Uses thus far have been limited because of its high cost. Krypton gas presently costs about 30/1. 

Radiorelease methods are based on the same principle the substance to be determined is brought into contact with another substance containing a radionuchde reagent, and by their interaction a certain amount of the radionuclide is released and measured. For this method substances loaded with Kr (radioactive kryptonates), for example krypton clathrates, may be applied. By reaction with oxygen Kr is released and can be measured continuously. Oxygen dissolved in water can be measured by reaction with jj deposited on Cu 204 jj jg oxidized and released into the... 

Recently experiments with the clathrate of hydroquinone and krypton have been carried out in a similar way at 25°C. The result was pKr = 0.40 atm and again y = 0.34, thus proving the validity of the generalized form of Raoult s law (Eq. 25 ). 

Ashbaugh, H. S. Asthagiri, D. Pratt, L. R. Rempe, S. B., Hydration of krypton and consideration of clathrate models of hydrophobic effects from the perspective of quasichemical theory, Biophys. Chem. 2003,105, 323-338... 

Radon forms a series of clathrate compounds (inclusion compounds) similar to those of argon, krypton, and xenon. These can be prepared by mixing trace amounts of radon with macro amounts of host substances and allowing the mixtures to crystallize. No chemical bonds are formed the radon is merely trapped in the lattice of surrounding atoms it therefore escapes when the host crystal melts or dissolves. Compounds prepared in this manner include radon hydrate, Rn 6H20 (Nikitin, 1936) radon-phenol clathrate, Rn 3C H 0H (Nikitin and Kovalskaya, 1952) radon-p-chlorophenol clathrate, Rn 3p-ClC H 0H (Nikitin and Ioffe, 1952) and radon-p-cresol clathrate, Rn bp-CH C H OH (Trofimov and Kazankin, 1966). Radon has also been reported to co-crystallize with sulfur dioxide, carbon dioxide, hydrogen chloride, and hydrogen sulfide (Nikitin, 1939). 

Trofimov, A. M. and Kazankin, Yu. N., Clathrate Compounds of p-Cresol with Noble Gases. II. Compound of p-Cresol with Krypton and Radon, Radiokhim. 8 720-723 (1966). 

Kroll process, 13 84-85 15 337 17 140 in titanium manufacture, 24 851-853 Kroll zirconium reduction process, 26 631 KRW gasifier, 6 797-798, 828 Krypton (Kr), 17 344 commercial, 17 368t complex salts of, 17 333-334 doubly ionized, 14 685 hydroquinone clathrate of, 14 183 in light sources, 17 371-372 from nuclear power plants, 17 362 physical properties of, 17 350 Krypton-85, 17 375, 376 Krypton compounds, 17 333-334 Krypton derivatives, 17 334 Krypton difluoride, 17 333, 336 uses for, 17 336... 

Handa, Y.P. (1986b). Calorimetric determinations of the compositions, enthalpies of dissociation, and heat capacities in the range 85 to 270 K for clathrate hydrates of xenon and krypton. J. Chem. Thermodynamics, 18 (9), 891-902. 

Krypton is an inert gas element. Its closed-shell, stable octet electron configuration allows zero reactivity with practically any substance. Only a few types of compounds, complexes, and clathrates have been synthesized, mostly with fluorine, the most electronegative element. The most notable is krypton difluoride, KrF2 [13773-81-4], which also forms complex salts such as Kr2F3+AsFe [52721-23-0] and KrF+PtFF [52707-25-2]. These compounds are unstable at ambient conditions. Krypton also forms clathrates with phenol and hydroquinone. Such interstitial substances are thermodynamicahy unstable and have irregular stoichiometric compositions (See Argon clathrates). 

If the trapped gas is radioactive with a high gamma-ray emission, such as krypton-79, which has a half-life of 34 hrs, the clathrate may then... 

Radon forms a series of clathrate compounds similar to those of krypton, xenon, and argon (e.g. Rn-6H20, RnGCeHsOH, Rn-3/ -ClC6H40H). 

Another example of crystals containing more than one component is provided by the clathrates. In clathrates of, 3-quinol, three quinol molecules are hydrogen bonded together to form an approximately spherical cavity of radius 4 A (Figure 15.13). Any molecule of appropriate size such as oxygen, nitrogen, krypton, xenon, methane, sulfur dioxide, or methyl alcohol can be trapped, and if it is not disordered within the clathrate, its location and orientation can be determined in the crystalline state by X-ray diffraction methods. In most cases, when a clathrate is... 

Clathrates provide cavities of a specific size and shape and therefore they can be used very effectively for separating gases with different sizes of molecules. For example, urea clathrates have been used to separate linear from branched hydrocarbons. The hydroquinone clathrate can be used to store and deliver radioactive krypton. In addition, if the host is chiral, there can be chiral discrimination so that one enantiomer of a guest is enclosed in the clathrate structure in preference to the other enantiomer. The trapped guest molecules can be liberated, for example, by solution in an apolar solvent, at the convenience of the user,... 

When quinol is crystallised from aqueous solution in the presence of argon at 40 atmospheres, the solid has the properties of quinol but contains argon which is set free when the quinol is melted or dissolved. The gas molecule is trapped inside a cage of hydrogen-bonded quinol molecules (Powell, 1948). Clathrates are formed by krypton, xenon and such gases as... 

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