Shock compression of liquid carbon monoxide and methane to 90 GPa (900 kbar)

Dynamic equation-of-state data for liquid CO and CH4 were measured in the shock pressure range 5–92 GPa (50–920 kbar) using a two-stage light-gas gun. The liquids were shocked from initial states near their saturation curves at 77 and 111 K for CO and CH4, respectively. The experimental technique used to double-shock CH4 is described. The CO data were examined by using three theoretical models: (1) a chemically nonreactive model, (2) a quasi-chemical-equilibrium model that allows CO to dissociate into gaseous species and graphite, and (3) a chemical-equilibrium model that also includes a dense carbon phase which exists at higher pressures and temperatures than graphite. This dense phase is assumed to be diamond. Our analysis shows that at low pressure chemical equilibrium takes much longer than a typical shock passage time. As a consequence, the experimental data initially follow the nonreactive Hugoniot to pressures well beyond the chemical dissociation limit. Both the experimental data and the Hugoniot computed with case (3) agree satisfactorily at high pressure. Further consequences of these observations to high-explosive studies are discussed. The theoretical analysis for the CH4 data was presented in an earlier paper.