PHYSICAL-CHEMISTRY OF THE H2SO4/H2O BINARY-SYSTEM AT LOW-TEMPERATURES - STRATOSPHERIC IMPLICATIONS

Laboratory experiments have been carried out to investigate the physical chemistry of the H2SO4/H2O binary system under conditions characteristic of the stratosphere. Water vapor pressures of sulfuric acid solutions (20-70 wt %) and of liquid-solid and solid-solid phase coexistence systems have been measured by mass spectrometry at temperatures between 190 and 240 K. Infrared spectra of the liquid. supercooled liquid, and crystalline hydrates of this system have also been investigated. The results indicate that some of the hydrates of sulfuric acid (i.e., H2SO4-4H2O, H2SO4.6.5H2O, and H2SO4.8H2O) may form and persist under the temperature and water partial pressure conditions typical of the high-latitude stratosphere.