High pressure (beyond 10,000 atm.) is a relatively new tool in
chemistry. Beyond 10,000 atm. the chemist deals primarily with
liquids or solids since most gases transform to a condensed phase at
such pressures unless the temperature is rather high. As a matter of
fact, most ordinary liquids transform to solids at a pressure of 10,000
atm. The most resistant liquid to solidification presently known is
a 50-50 mixture of riornial pentane and isopentane. This mixture
solidifies somewhere in the vicinity of 35,000 atm. at room temperature.