Читать книгу Geochemistry - William M. White - Страница 37

The compressibility and coefficient of thermal expansion parameters allow us to construct an equation of state for any substance. Such an equation relates the fundamental properties of the substance: its temperature, pressure, and volume. The partial differential of volume with respect to temperature and pressure is such an equation:

(2.17)

Substituting the coefficient of thermal expansion and compressibility for ∂V/∂T and ∂V/∂P respectively we have:

(2.18)

Thus, to write an equation of state for a substance, our task becomes to determine its compressibility and coefficient of thermal expansion. Once we know them, we can integrate eqn. 2.18 to obtain the equation of state. These, however, will generally be complex functions of temperature and pressure, so the task is often not easy.