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.
Liquid metals and vapours under pressure
Abstract This review covers experimental and theoretical work on the properties of liquid metals under pressure, both at higher than normal densities near the normal melting point, and at lower densities in the region of the critical point. Information about the equation of state is summarized in section 2, together with some properties of the equilibrium vapour phase. The measurement and prediction of critical point data, and the application of the law of corresponding states, are discussed in section 3. Electrical measurements, in particular of the electrical conductivity, are reviewed in section 4; the extent to which present theories are adequate, and the theory of the metal-insulator transition, are also considered.
HIGH-TEMPERATURE SOLAR CHEMICAL REACTORS FOR HYDROGEN PRODUCTION FROM NATURAL GAS CRACKING
This study deals with the thermal cracking of natural gas for the coproduction of hydrogen and carbon black from concentrated solar energy without CO2 emission. A laboratory-scale solar reactor (1 kW) was tested and modeled successfully. It consists of a tubular graphite receiver directly absorbing solar radiation, in which a mixture of Ar and CH4 flows. A temperature increase or a gas flow rate decrease results in chemical conversion increase. Methane conversion higher than 75% was obtained. Reaction occurred near the wall where temperature is maximal and gas velocity is minimal due to the laminar flow profile. The work focused also on the design of a medium-scale tubular solar reactor (10 kW) based on the indirect heating concept. A reactor model including gas hydrodynamics and heat and mass transfers coupled to the chemical reaction was developed in order to predict the reactor performances. Temperature and species concentration profiles and final chemical conversion were quantified. According to the results, temperature was uniform in the tubular reaction zone and the predicted chemical conversion was 65%, neglecting the catalytic effect of carbon particles.