Slope anomaly in the vapour pressure curve of Hg
The investigation of normally-metallic fluids at reduced densities has created considerable experimental and theoretical interest. Hensel1 has presented evidence for transitions, related to electronic properties, in both the liquid and vapour phases of Hg, and predicted that these would affect the liquid–vapour transition. We present here evidence that the vapour pressure curve of Hg, p(T), has an unusual and probably unique form in that the In p against 1/T plot showed a sharp change of slope at temperature T = T′ = 1,361 K and saturated liquid density ρL = 10.7 g cm−3. The latter is about the density at which Hensel1 deduced that the electronic mean free path equalled the mean interatomic spacing, and which he took to be associated with the electronic-property related transition in the liquid phase.
Thermoelectric power near the critical point of expanded fluid mercury
It has been suggested in the past that the thermoelectric power of expanded fluid mercury near the critical density rapidly decreases to zero. A new experiment has been performed to check whether this is really so or whether the observations can be attributed to the effect of high temperature on the other materials in the measuring system. It is concluded that the thermoelectric power of Hg really does cease to vary monotonically with temperature near the critical point and that it changes sign twice. This behaviour is tentatively connected with the critical point itself and the situation is discussed. The critical point is found to be at pc=0.1675+or-0.0025 GPa and Tc=1495+or-8 degrees C.
Self-diffusion in liquid sodium at constant volume and constant pressure
Abstract The self-diffusion coefficient of liquid sodium has been determined in the temperature range melting point to 300°C, under both constant pressure and constant volume conditions. The experimental technique is described in detail and current theories are reviewed in the light of the results obtained. None of the theoretical approaches is entirely correct in predicting the experimentally observed data. This is probably because there is more than one diffusion process operative in the liquid. It is, however, concluded that models of the fluctuation type most accurately describe observed conditions. The critical fluctuation concept is thought not to be applicable.