Recently, our view of the Earth¿s lower mantle changed dramatically. It had been thought that two major phases were present in all the lower mantle: MgSiO3-perovskite (PV) and (Mg,Fe)O. In 2004, it was found that the pressure and temperature just above the core-mantle boundary (CMB) will induce a transition in MgSiO3 to a ¿post-perovskite¿ (PPV) phase, now thought to be the origin of the thin D'' seismic zone extending into the mantle to ~200 km from the CMB. Understanding D'' is vital as core-mantle interactions, e.g. heat flow, pass through it. As PPV-MgSiO3 is stable only at megabar pressures, its properties are very difficult to measure; instead we must use computer simulation and experiments on analogues. CaPtO3 is the best low-P analogue available; we wish to measure the temperature dependence of its bulk modulus, no such measurements having been made for any PPV analogue phase.