High temperature-high pressure experiments on H2O-N2

Abstract

Abstract The investigation of binary systems in a diamond anvil cell (DAC) reported in literature is limited to about 500 K. In order to extent these investigations to more complex systems like water-nitrogen, the accessible temperature range should be increased considerably. Apart from a high temperature DAC, there is a need for a loading system operating at temepratures as high as 700 K. The technical details of such a set-up and the procedure for the preparation and loading of the DAC with a mixture of known composition are described in this paper. Two important and interesting features of the phase diagram of water-nitrogen at high temperature are the fluid-fluid coexistence surface and the critical curve. This area has only been investigated up to 250 MPa. As an example to show the usefulness of the equipment we present for a mixture containing 67 mole percent of water, the fluid-fluid transitions in the range from 0.13 to 1.73 GPa and 650 to 816 K. This isopleth does not go to as high pressures as might be exspected from low pressure literature data.