|
This run features an aqueous solution that is approximately 15.5 wt.% Na2SO4. Initially, the pressure was about 151 MPa. 11/07/14 12:41:41: The system starts as all liquid at nearly a pressure of 151 MPa and a temperature of nearly 300 K. Upon cooling, the volume decreases as the liquid contracts. 11/07/14 15:43:30: The system is supercooled to 282.5 K, at which point mirabilite crystals grow rapidly and the volume increases. Further cooling brings only slight additional mirabilite growth. 11/07/14 18:13:30: Around 250 K, the volume and pressure jump up as Ice Ih begins forming, though it is not immediately visible in the window. 11/07/14 18:33:30: Ice dendrites are now visibly growing, and soon the chamber is filled with small crystals that block the light. With the connecting tubing frozen, the pressure and volume transducers may not accurately reflect the conditions inside the chamber. As the system is warmed, there is visible melting in the window, but no significant changes are registered in the volume until the material softens sufficiently. 11/07/15 13:23:30: The volume and pressure both start dropping as the window begins to clear, signifying the onset of significant melting. The temperature of 250.6 K is well below the expected eutectic temperature of about 256 K for this pressure, indicating that the pressure inside the capsule is still significantly different from that indicated by the sensor, or that this is a different phase of material. Upon cooling, the voltage and pressure did increase again, but regrowth was not visible in the window. 11/07/15 16:41:30: There appears to be substantial liquid in the cell. We started to lower the pressure to prepare for the next run.
|