Experimental study on the stability of oxalic acid and carbon dioxide manometer.

In this study, diamond-anvil cell combined with Raman spectroscopy are applied to in situ investigate the stability of oxalic acid. The oxalic acid can preserve stably at low temperature and high pressure, however it will decompose into CO, and H2O under the conditions of high temperature and low pressure. When the ore-forming fluids encountered the fracture, the organic complexes would be transformed into CO, quickly both by the elevated temperature and the decrease of pressure. Consequently, the metals will precipitate and concentrate in favorable space. In addition, the physical and chemical properties of carbon dioxide are also studied. The equation for determining the pressure of CO2-rich inclusions by Raman shift of CO, is P(MPa) =271. 517 center dot (Delta nu(1381.93) - 0. 010987 center dot Delta T) +0. 1, where Delta vi(138.93) (cm(-1)) is the Raman shift (cm') relative to that of the 1381. 93cm(-1) line at 0. 1MPa and ambient temperature, AT is the temperature relative to 23 degrees C, P(MPa) is the inner pressure of the inclusion. The standard deviation of Raman shift is +/- 0. 2cm(-1) and the uncertainty of pressure is 54MPa. This equation is suitable for pressure calibration under high pressure between 23 degrees C and 390 degrees C.