E. U. Franck

Water and aqueous solutions at high pressures and temperatures

A survey is given of recent results on properties of water and aqueous solutions at high pressures and high temperatures with emphasis on supercritical conditions. New PVT-data for water from static measurements are available to 1000°C and 10 kb. Dielectric constants and viscosity have been measured to 550°C and 5 kb. Infra-red and Raman spectra of OD-vibrations of HDO in F120 to 400°C and 5 kb give information about the extent of hydrogen bonded structure. Critical curves of binary aqueous systems with one inert component, for example argon, extending to 3 kb and 400°C are discussed. Absorption spectra of bivalent cobalt and nickel chlorides are measured to 500°C and 6 kb and conclusions about the stability of octahedral and tetrahedral complexes are drawn. Shock wave and static conductance measurements to 1000°C and more than 100 kb demonstrate the increase of the ion product of water by twelve orders of magnitude or more at these conditions.

Critical curves and phase equilibria of water-n-alkane binary systems to high pressures and temperatures

Abstract The critical curves of the six binary systems water-methane to water-hexane and water-dodecane have been calculated up to 200 MPa and, in part, to 670 K. An equation of state of the perturbation type with a repulsion and an attraction term with square-well potential for intermolecular interaction is used. With pairwise combination rules for these potentials, three adjustable parameters are needed. The values of these parameters for the series of alkanes obtained from comparison with experiments are given and discussed. For water with methane, butane, and hexane the extent of the three-dimensional two-phase regions is calculated. It is suggested to use this procedure as a basis for predictions for analogous binary polar-nonpolar systems to high pressures and temperatures.

Concentrated electrolyte solutions at high temperatures and pressures

A survey is given of recent experimental results obtained from high-temperature, high-pressure investigations with water, aqueous solutions, and ionic fluids. Data on the static dielectric constant of water to 550°C and 5 kbar are given and discussed with respect to their relation to water structure. Infrared and Raman spectra of HDO in pure water have been obtained to 400°C and 4 kbar, which give information on hydrogen bonding. Xe−H2O and CO2−H2O mixtures were investigated in the infrared. Ni(II) and Cu(II) complexes were investigated by absorption spectroscopy in aqueous solutions of high chloride content to 350°C and 2–6 kbar. The gas-liquid critical point of ammonium chloride was found at 880°C and 1635 bars. This fluid appears to be predominantly ionic even in the critical region. The possibility of converting pure polar fluids such as ammonia and water into concentrated ionic solutions by self-ionization at very high pressures is mentioned.

Polar and ionic fluids at high pressures and temperatures

A survey and critical discussion is given of recent experimental investigations of thermodynamic and related properties of water, aqueous mixtures, other polar fluids certain fused salts and fluid metals Results cover a range of pressures to several kbar and of temperatures extending to 1000°C and beyond. For supercritical water, P VT-data, thermal conductance, Raman spectra, dielectric constant and ionic dissociation are discussed and m part compared with the properties of dense supercriticai hydrogen chloride and ammonia. Recently determined critical curves of binary systems ith water or ammonia combined with non-polar second components such as rare gases and hydrocarbons are given. Vapour pressure. density and conductance measurements are presented for fluid and supercritical bismuth trichioride and ammonium chloride. The last salt may be the first example of a predominantly ionic fluid at critical conditions. For mercury, caesium and potassium the vapour pressure curve has been measured to the critical point. Conductance measurements at supercritical conditions show the continuous transition from insulating to metallic states with increasing density. Certain experimental details for high pressure--high temperature cells are presented, which may be useful for various applications.

The viscosity of n-decane to high temperatures of 573 K and high pressures of 300 MPa

The dynamic viscosity of liquid n-decane has been measured with the “Oscillating Disk Method” from 293 K to 573 K and from 0.1 MPa to 300 MPa. A high pressure autoclave of 50 mm internal diameter contained between two rigid disks an oscillating stainless steel disk of 44 mm diameter suspended on a platinum-tungsten wire. Pressure was generated with a spindle press filled with a suitable hydraulic fluid separated from the n-decane. Thus heating and pressure variation could be performed at selected constant volumes. The density dependence of the viscosity could be determined. The viscosity increases at 373 K from 375 to 1602 μPa s in the pressure range from 0.1 to 200 MPa, at 473 K from 200 to 1114 μPa s in the pressure range from 10 to 300 MPa, and at 573 K from 223 to 675 μPa s in the pressure range from 60 to 300 MPa. The mean accuracy of the viscosity measurements is about 1.3 %. A polynomial function describing the viscosity variation with pressure and temperature is given. The maximum average deviation is 0.46 %, the mean average deviation between measured and calculated data is 0.11 %. The viscosity as a function of density is also shown. With Arrhenius plots, the energies of activation are obtained.

Supercritical Water and Other Fluids — A Historical Perspective

Dense, supercritical high pressure fluids find rapidly increasing interest in science and industry. Experimental research at the Institutes for Physical Chemistiy of Gottingen and Karlsruhe Universities has accompanied this development since the 1950’s. With am adequate selection of examples, a historical perspective will be attempted which is personal and cannot be representative of the development in the field in general. Supercritical water is the most important fluid. My own interest was initiated in 1953 by c. W. Correns of Mineralogy in Gottmgen, who slowed me that quarte and alkali halides dissolve in dense steam. TMs stimulated our investigation of electrolytic dissociation within a wide range of high temperatures and pressures along with other thermophysical properties of aqueous systems and related fluids.

Aqueous mixtures to supercritical temperatures and at high pressures

Proprietes thermophysiques, en particulier la permittivite dielectrique. Binaires eau et H 2 , N 2 , O 2 , CH 4 , He

Dense fluids—New aspects and results

Abstract Dense fluids at elevated and supercritical temperatures find increased interest in science and technology. In this presentation special attention is given to binary mixtures with polar components. Methods and results of experiments with such high pressure-high temperature fluids are described. Far infrared spectra of CHCIF 2 and CHF 3 give indications of the types of molecular motion in the supercritical phases. “Enhancement factors” for the solubility of a solid solute like caffeine in high pressure CO 2 have been determined spectroscopically. The phase diagrams in the pressure-temperature-composition space and critical curves for water combined with nitrogen, oxygen, methane and helium have been measured recently to 2500 bar and 450°C. A “rational” equation of state permits calculation of critical curves and binodal surfaces for such systems. An extended investigation was made with the ternary system water-methane-sodium chloride. Small additions of salt shift critical curves by 100°C and more to higher temperatures. In water-methane mixtures between 400 and 500°C and at 1000 bar “supercritical flames” and “hydrothermal combustion” could be produced with injected oxygen. Binary liquid mixtures of cesium and cesium hydride to elevated hydrogen pressure and to 800°C show the phenomena of continuous transition from metal to ionic fluids. Electric conductance measurements in the whole range of concentrations are presented and discussed.

Phase equilibria and critical phenomena of the ternary system H2OCH4NaCl to 500°C and 2500 bar

Abstract The system of water and methane with addition of minor quantities of sodium chloride permits to study the extent of the water-methane two-phase region and critical curve by an added electrolyte. The system is also of interest in relation to mineral forming hydrothermal fluids and to natural gas deposits. Experimental determinations of the phase boundary surface in the three-dimensional pressure-temperature-composition space were made with an especially designed high pressure vessel with variable volume, a sapphire window and a pair of internal electrodes to facilitate detection of phase separations. Water-methane ratios from 0.1 to 0.9 have been used. Water-salt contents of 0.6, 1.7 and 8 weight percent, relative to water, were applied. The addition of NaCl shifts the upper miscibility limiting temperature at 1000 bar from 360°C for salt-free water-mathane to 430 and 490°C with the lowest and highest of the three salt contents.

Experimental Studies of Compressed Fluids

With high pressures at elevated and supercritical temperatures fluids can be studied over a very wide range of density. Fluids with strongly interacting polar molecules - for example water - are of particular interest. Results for several thermophysical properties are presented. PVT-data of sodium, high pressure-high temperature viscosity of decane and the dielectric constant of supercritical water-benzene mixtures are discussed. The continuous transition from ionic to metallic states is shown with the cesium-cesium hydride system to 800 °C. High pressure far-infrared spectroscopy reveals the dynamics of compressed polar methyl halides. Quantitative determinations of the solubility of solids in dense supercritical gases are presented. A number of phase diagrams and critical curves of binary aqueous systems to 400 °C and 2000 bar have been determined. A new rational equation of state for such systems is presented. “Hydrothermal” combustion of methane in supercritical water is possible and a flame, burning at 1000 bar is shown.