Editing Calorimetry (section)

===Compressibility at constant temperature===

For measurements at experimentally controlled temperature, it is again assumed that the volume <math>V\ </math> of the body of calorimetric material can be expressed as a function <math>V(T,p)\ </math> of its temperature <math>T\ </math> and pressure <math>p\ </math>, with the same provisos as mentioned just above.

The quantity that is conveniently measured at constant experimentally controlled temperature, the isothermal compressibility, is defined by <ref name="LR 54"/><ref name="Guggenheim 38"/><ref name="Callen 84"/><ref name="Adkins 38"/><ref name="Bailyn 49"/><ref name="Kondepudi 180"/>

:<math>\kappa _T(T,p)\ = -\frac{1}{V(T,p)}{\left.\cfrac{\partial V}{\partial p}\right|_{(T,p)}} </math>