Reference materials for piston-displacement pressure-volume measurements: Indium, lead, and NaCl

Measurements of the room temperature compressions of NaCl, lead, indium, and indium-jacketed iron together with published results for these materials have been used to evaluate the piston-displacement technique for obtaining pressure-volume relations. The internal consistency of these measurements appears to be better than +- 5 x 10-4 in V/V0 at 20 kbar, which suggests a comparable accuracy. Indium, for which published data show appreciable discrepancies, is a very useful material since it is relatively incompressible and retains its plasticity to very low temperatures. The resulting pressure-volume relation for indium can be represented by a Murnaghan relation with B0 = 397 kbar and B/sup prime/0 = 5.45, and an estimated accuracy in the 20-kbar room temperature compression of 1%. The temperature dependences of these equations of state also are discussed