Composition of Tetrahydrofuran Hydrate and the Effect of Pressure on the Decomposition

Abstract

The decomposition temperature of the structure II 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 III and II, 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 II hydrates shows no statistical evidence of departure from the ideal composition of 17 mol of water per mol of hydrate former.