Specific Heat Measured at High Pressures by a Pulse Method

The classical electric pulse technique has been adapted to measurements of specific heat at high pressure. A wire specimen is heated by a 100 μsec pulse, stabilized at I = 50 A. The resulting temperature rise is extracted from the voltage drop U over the sample by means of a bridge circuit. The specific heat is obtained from the formula cp = C(T,P)U I / m ė, where C(T,P) is a function to be experimentally determined for a given sample, m the mass of the sample, and ė the time derivative of the bridge output voltage. A procedure has been developed for in situ corrections of ė for heat loss to the medium surrounding the wire. Digital techniques are used for the pulse analysis. The method has been used to ascertain the pressure dependence of cp for Cu up to 100 kilobars at room temperature. The relative change in cp was found to be 2.8 × 10−4/kilobar.