H2O loss during piston-cylinder experiments

The capsule materials Au, Ag75Pd25, and Pt, were tested for permeability to C-H-O fluids in a piston-cylinder apparatus at 10 kbar and 900-1100 degree s C. The capsules were embedded in boron nitride. After the experiments, th e C-H-O fluids were analyzed by gas chromatography to determine the oxygen content of the capsules. No significant loss of oxygen was observed in any capsule material at tempe ratures less than or equal to 1050 degrees C. At 1100 degrees C, however, a which is above the melting point of Au and Ag75Pd25 at 10 kbar, oxygen los s from Pt capsules amounted to between 12 and 80%, over a period of 6 days. These results were confirmed by experiments performed using pure H2O as th e fluid. Water loss during piston-cylinder experiments is a serious problem. A tempe rature of about 1050 degrees C represents the upper thermal limit for const ant H2O-containing systems.