The experimental results are presented on the investigation of isentro
pic expansion of solid specimens of aluminum, iron, molybdenum, lead,
and tantalum, compressed by shock waves of an amplitude from 10 to 200
GPa. The data obtained are used to determine the range of validity of
the approximation within which the isentropes on pressure-mass veloci
ty diagrams are replaced by the mirror reflections of shock adiabats.