Shock compression of formic acid

Abstract

Simple molecules such as formic acid, HCOOH, have been suggested to play important roles in the origin of life due to their high pressure and temperature chemistry. The hydrogen bonding characteristics and polymerization of HCOOH under static high pressure have been recently investigated using both molecular dynamics calculations and experimental work. These works suggest that symmetric hydrogen bonding of HCOOH (forming a linear chain polymer where all C-O bonds are equivalent) occurs at 16 - 21 GPa at room temperature. In order to examine the shock compression behavior of this simple carboxylic acid, we present a series of gas gun-driven plate impact experiments on formic acid with shock inputs in the range of 5.5 - 23.0 GPa. Using in-situ electromagnetic gauges, shock wave profiles (particle velocities) were measured at multiple positions as a function of shock input pressure, providing valuable information about its unreacted equation of state. No easily recognizable shock-induced reactions were observed in any of the four experiments, and the four points lie close to a universal liquid Hugoniot based only on the sound speed of formic acid. © 2012 American Institute of Physics.