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Ammonia-water mixtures at high pressures - Melting curves of ammonia dihydrate and ammonia monohydrate and a revised high-pressure phase diagram for the water-rich regionThe phase relations of some mixtures of ammonia and water are investigated to create a phase diagram in pressure-temperature-composition space relevant to the geophysical study of bodies in the outer solar system. The mixtures of NH3(x)H2O(1-x), where x is greater than 0.30 but less than 0.51, are examined at pressures and temperatures ranging from 0-6.5 GPa and 125-400 K, respectively. The ruby luminescence technique monitors the pressure and a diamond-anvil cell compresses the samples, and the phases are identified by means of normal- and polarized-light optical microscopy. The melting curve for NH3H2O(2) is described by the equation T = 176 + 60P - 8.5P squared for the ranges of 0.06-1.4 GPa and 179-243 K. The equation for NH3H2O is T = 194 + 37P - P squared, which represents a minor correction of a previous description by Johnson et al. (1985). Observed phase transitions are consistent with the high-pressure stability limit of NH3H2O(2), and the transition boundary is found to be linear.
Document ID
Document Type
Conference Paper
Boone, S.
(California Univ. Los Angeles, CA, United States)
Nicol, M. F.
(California, University Los Angeles, United States)
Date Acquired
August 15, 2013
Publication Date
January 1, 1991
Subject Category
Lunar And Planetary Exploration
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: Houston, TX
Country: United States
Start Date: March 12, 1990
End Date: March 16, 1990
Accession Number
Funding Number(s)
Distribution Limits

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