Phase Diagram and Heat Capacities of the Malonic Acid/Water System
Abstract
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 C3H4O4ṡ6H2O. 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.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFM.A51F0754H
- Keywords:
-
- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0305 Aerosols and particles (0345;
- 4801);
- 0320 Cloud physics and chemistry;
- 1610 Atmosphere (0315;
- 0325)