1. Properties of ultra-high-pressure fluids

1.1 Compressibility of fluids

Several quantities can be defined to characterize gas compression. Here are a few of them.

Compressibility pV is the product of pressure p and volume V, and the virial coefficients are the coefficients in the limited expansion of pV as a function of the inverse of volume or pressure. The development as a function of 1/V is the more fundamental of the two:

For low-density gases (whose molar volume is greater than the critical...