Simulating Weathering of Ignitable Liquids to Understand the Effect of Mole Fraction on Weathering

Evan Ferweda*, Ahna Kotula*, Caitlyn Wensel and Glen P. Jackson, Department of Forensic and Investigative Science, C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV 26506

Field (Broad Category): Forensics (Physical Sciences & Engineering) 

Student’s Major: Forensic Chemistry 

The ultimate goal of this project is to enable fire debris analysts to make more reliable predictions about the presence of ignitable liquids in fire debris samples. Towards that end, this study continues the development of a mathematical model to describe the composition of residues left behind when ignitable liquids, like gasoline, evaporate over time. Our previously published model, based on standard principals of ideal mixtures and ideal gases, was designed to predict how ignitable liquids would weather at different temperatures. That study determined that temperature has a significant effect on how ignitable liquids weathered, or evaporated, over time. The current study aims to establish how sensitive the model is to the molar fraction of each component of the mixture, and whether or not the model can be simplified. For example, if a particular component decreases below a certain mole fraction threshold, the term for mole fraction could become irrelevant or constant. To better understand this concept, the current model was edited to account for solutions up to 20 components and with a wider diversity of mole fractions than previously attempted. This poster will describe model that is used to simulate the weathering of different hypothetical mixtures and will discuss the relationship between the initial mole fractions and instantaneous mole fractions as a function of evaporation time or weathering. Other members of the group are currently validating the model with actual weathering of synthetic mixtures that replicate the simulations, and that work is to be presented in a complementary poster. 

Funding: National Institute of Justice 

Program/mechanism supporting research/creative efforts: WVU 497-level course