Isothermal compressibility pkTx=<△N2→vr/<N>r aP kT(O<N> HVT /OW)VT<ANZ>HVTIsothermal compressibility kTχT = <DN2> mVT/<N>mVT ( ) T P T V V   =− 1  kT(<N>mVT /m)V,T = <DN2> mVT