Mixtures of ammonia and water and of methane and water at high pressures.

摘要

I have examined the phase relations of mixtures of ammonia and water, {dollar}rm (NHsb3)sb{lcub}X{rcub}Hsb2O)sb{lcub}1-X{rcub},{dollar} with compositions 0.32 {dollar}<{dollar} X {dollar}<{dollar} 0.51, at pressures from 0 to 6.5 GPa, and at temperatures from 125 to 400 K. Sample pressures were determined by the ruby luminescence technique. The sample temperature was controlled by mounting the diamond cell in a vacuum cryostat where the diamond cell was cooled by a static heat sink and heated electrically. Microscopic observations were made in situ and were recorded on video tape. Polarizing filters were used to observe and record birefringence and other optical effects. I found that the congruent melting curve of ammonia dihydrate, {dollar}rm NHsb3{lcub}cdot{rcub}2Hsb2O,{dollar} extends from 0.06 GPa and 179 K to 1.4 GPa and 243 K and conforms to the equation, T = 176 + 60P {dollar}-{dollar} 8.5P{dollar}sp2{dollar} where T is temperature in K and P is pressure in GPa. Above 1.4 GPa, {dollar}rm NHsb3{lcub}cdot{rcub}2Hsb2O{dollar} was found to melt incongruently to form Ice VII and fluid. The congruent melting curve of ammonia monohydrate, {dollar}rm NHsb3{lcub}cdot{rcub}Hsb2O,{dollar} was found to extend from atmospheric pressure to 4.8 GPa and 350 K and to conform to the equation, T = 194 + 37P {dollar}-{dollar} P{dollar}sp2{dollar}. At higher pressures, it is presumed that {dollar}rm NHsb3{lcub}cdot{rcub}Hsb2O{dollar} melts incongruently to form Ice VII and fluid. A phase diagram for the high-pressure ice polymorphs and the ammonia hydrates in the water-rich region is presented.; I have examined samples of methane and water which were loaded into a diamond cell as methane hydrate clathrate using optical observations and Raman spectroscopy at conditions ranging from 296 to 323 K and at pressures from 0.4 to 5.0 GPa. The spectral results indicate that methane hydrate decomposes to high pressure ices and solid methane at pressure above 2.0 GPa at 295 {dollar}pm{dollar} 5 K. Microscopic examination indicates the presence of a single phase at pressures above 2.3 GPa which tends to contradict the spectral data. The transition from methane hydrate to ice and solid methane seems to cover a broad range of pressure, from 1.0 to 2.0 GPa.