The decomposition temperature of the structure I1 clathrate hydrate of tetrahydrofuran has been followed to pressures above 3 kbars, where the hydrate is found to decompose incongruently in the regions of stability of ices I11 and 11, with no evidence of formation of a denser hydrate. From measurements of liquid solution densities and of volume changes at hydrate decomposition the density of the hydrate was obtained. Comparison with the X-ray lattice dimension indicates that at least 98% of the large cages are occupied, the principal uncertainty being in the lattice parameter. A similar treatment is made of Tammann and Krige's data (23) for chloroform hydrate. Analysis of the results of 18 composition determinations of structure I1 hydrates shows no statistical evidence of departure from the ideal composition of 17 mol of water per mol of hydrate former.La temperature de dCcomposition du clathrate hydrate de structure I1 du tktrahydrofuranne a Ct C suivie jusqu'a des pressions superieures a 3 kbar; il a kt6 trouve que dans ces regions de stabilitk des glaces I11 et I1 l'hydrate se decompose d'une f a~o n aberrante sans preuve de formation d'un hydrate plus dense. A partir des mesures de densite des solutions liquides et des changements de volume a la dCcomposition de I'hydrate, il a Ct C possible d'obtenir la densite de l'hydrate. La comparaison avec la dimension du reseau obtenu par rayons X indique qu'au moins 98% des grandes cages sont occupees, ]'incertitude principale &ant dans le parametre retuculaire. A partir des donnCes de Tamman et Krige une analyse similaire est effectuee pour le chloroforme hydrate. Les analyses des resultats se rapportant a 18 determinations de composition d'hydrates ayant la structure I1 ne montrent aucune preuve statistique d'ecart par rapport la composition idkale de 17 mol d'eau par mole de gCnCrateur d'hydrate. Canadian Journal o f Chemistry, 49, 2691 (1971)Among the diverse molecules now known to therefore most easily distinguished from ice and form "gas hydrates" of von Stackelberg's has been chosen for further study. structures I and I1 (1) are a number of ethers and Tetrahydrofuran hydrate was first reported ketones which are distinguished from the classical by Palmer (10) who found from melting point us. gas-hydrate formers by their solubility in water concentration curves a composition of between and by the possibility of hydrogen bonding with 13 and 16 molecules of water per molecule of the host water molecules bf the clathrate struc-tetrahydrofuran (THF), with a probable formula tures. Ethylene oxide (2, 3) and trimethylene of THF.14H20. Erva (1 1) obtained a congruent oxide (4) form hydrates of type I. Structure I1 melting point of 4.38 "C at an approximate comhydrates are formed by dimethyl ether (I), by position of THF.16H20. Several nugatory irtrimethylene oxide, tetrahydrofuran, 2,5-dihydrofuran, propylene oxide, and 1,3-dioxolane (4, 5) and by acetone (6, 7) and cyclobutanone (5,8). With the exception of the study by Glew and Rath (9) of the variable composition o...

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Cubic ice Ic and hexagonal ice Ih were prepared in pressurizable dielectric cells at temperatures near − 110°C from the high-pressure ices II and IX. No differences were found between the dielectric properties of Ic and Ih. Freshly prepared samples exhibited longer relaxation times at low temperatures than those commonly found for samples of Ih prepared directly by freezing purified water. These long relaxation times became appreciably shorter with sample aging. These results are attributed to precipitation of impurities from ices II and IX, followed by their gradual reincorporation in the ice I lattice. At temperatures as high as − 50°C the isothermal sequence of transformations I→II→I is capable of producing a substantial degree of purification of ice I in terms of its dielectric relaxation time.

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Publication costs assisted by NRCC Dielectric measurements between 1.8 and 250°K are reported for the isostructural hydrates of tetrahydrofuran, trimethylene oxide, and acetone. The characteristic shape of the high-temperature absorption arising from reorientation of water molecules is better represented by two discrete relaxation times than by a continuous distribution of the Cole-Cole or Frohlich type. The activation volume for water reorientation, 4.4 ± 0.3 cm3 mol'1 for tetrahydrofuran hydrate at 211°K, is similar to values found in other disordered ices. At low temperatures, very broad absorption by the guest molecules and failure of the guest contribution to the permittivity to increase as 1/T show the perturbing effect of the variable (but relatively small) electrostatic fields of the orientationally disordered water molecules. Permittivities of 3.5 to 4.0 at 4°K for the three hydrates include large contributions from rotational oscillations of guest molecules at far-infrared frequencies. The relaxation rate of H2S in the small cages of the double hydrates exceeds 1 MHz at all temperatures down to 1.8°K.