HR: 0830h
AN: A51F-0754    [PDF]
TI: Phase Diagram and Heat Capacities of the Malonic Acid/Water System
AU: Hansen, A
EM: ahansen@mcw.edu
AF: Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226 United States
AU: * Beyer, K D
EM: keith_beyer@wlc.edu
AF: Wisconsin Lutheran College, Department of Chemistry 8800 W. Bluemound Rd., Milwaukee, WI 53226 United States
AB: Malonic acid is one of the more ubiquitous dicarboxylic acids found in the atmosphere and is quite soluble in water. Therefore, its impact on particle/cloud droplet formation needs to be better understood through the study of the thermodynamics of its aqueous solutions. The liquid/solid phase diagram and solution heat capacities of the malonic acid/water binary system have been investigated using differential scanning calorimetry and infrared spectroscopy of thin films. We report here the first measurement of the ice melting envelope as well as the ice/malonic acid eutectic temperature and composition in this binary system. Evidence from both thermal analysis and infrared spectroscopy is shown for a malonic acid hydrate, possibly C$_{3}$H$_{4}$O$_{4}\cdot$6H$_{2}$O. We have observed the formation of this hydrate over a large range of concentrations, and have found it is a major fraction of samples within that region. We have also determined the enthalpy of fusion of malonic acid as well as the constant pressure heat capacities of solutions in the concentration range 5 - 55 wt% malonic acid from 323 K to the freezing point of each solution.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 1610 Atmosphere (0315, 0325)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting