Experimental Insights into the Sulfuric Acid/Water Phase Diagram: Implications for Polar Stratospheric Clouds
Abstract
We have investigated the H2SO4/H2O binary liquid/solid phase diagram using a highly sensitive differential scanning calorimeter (DSC) and infrared spectroscopy of thin films. In particular we have sought to investigate the region from pure ice to sulfuric acid hemihexahydrate (SAH, H2SO4ú6.5H2O), including a detailed look at the sulfuric acid octahydrate (SAO). Our studies have found that there is a unique, repeatable IR spectra for SAO, which is not merely a combination of spectra of ice and sulfuric acid tetrahydrate (SAT), as has been previously suggested could be the case. From our DSC studies, we have identified the melting, or solid/solid phase transition of the octahydrate. We have also determined from our studies using the energy of fusion for SAO that SAO is a major component of H2SO4 solutions in the range 20 - 40 wt.% when they freeze. Our results indicate that SAO could be a significant portion of solid or partially frozen polar stratospheric cloud particles. As such, key stratospheric reactions should be studied on SAO surfaces.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2002
- Bibcode:
- 2002AGUSM.A41B..06B
- Keywords:
-
- 0305 Aerosols and particles (0345;
- 4801);
- 0320 Cloud physics and chemistry;
- 0340 Middle atmosphere: composition and chemistry