Melting curve and fluid equation of state of carbon dioxide at high pressure and high temperature

The melting curve and fluid equation of state of carbon dioxide have been determined under high pressure in a resistively heated diamond anvil cell. The melting line was determined from room temperature up to 11.1+/-0.1 GPa and 800+/-5 K by visual observation of the solid-fluid equilibrium and in situ measurements of pressure and temperature. Raman spectroscopy was used to identify the solid phase in equilibrium with the melt, showing that solid I is the stable phase along the melting curve in the probed range. Interferometric and Brillouin scattering experiments were conducted to determine the refractive index and sound velocity of the fluid phase. A dispersion of the sound velocity between ultrasonic and Brillouin frequencies is evidenced and could be reproduced by postulating the presence of a thermal relaxation process. The Brillouin sound velocities were then transformed to thermodynamic values in order to calculate the equation of state of fluid CO2. An analytic formulation of the density with respect to pressure and temperature is proposed, suitable in the P-T range of 0.1-8 GPa and 300-700 K and accurate within 2%. Our results show that the fluid above 500 K is less compressible than predicted from various phenomenological models.     

High temperatures and high pressures Brillouin scattering studies of liquid H(2)O+CO(2) mixtures

The Brillouin scattering spectroscopy studies have been conducted in a diamond anvil cell for a liquid mixtures composed of 95 mol?% H(2)O and 5 mol?% CO(2) under high temperatures and pressures. The sound velocity, refractive index, density, and adiabatic bulk modulus of the H(2)O+CO(2) mixtures were determined under pressures up to the freezing point at 293, 453, and 575 K. It is found from the experiment that sound velocities of the liquid mixture are substantially lower than those of pure water at 575 K, but not at lower temperatures. We presented an empirical relation of the density in terms of pressure and temperature. Our results show that liquid H(2)O+CO(2) mixtures are more compressible than water obtained from an existing equation of state of at 453 and 575 K.     

Volumetric,Acoustic and Refractive Index for the Binary System (Butyric acid + Hexanoic acid) at Different Temperatures

In this paper density, sound velocity, and refractive index for the binary system (butyric acid + hexanoic acid) were measured over the entire composition range and at 5 K intervals in the temperature range 293.15–313.15 K. The excess molar volumes, isentropic compressibilities, excess isentropic compressibilities, deviation in refractive indices, molar refractions, and deviation in molar refractions were calculated by using the experimental densities, sound velocities, and refractive indices, respectively. The Redlich–Kister equation was used to fit the excess molar volume, excess isentropic compressibility, deviation in refractive index and deviation in molar refraction data. The Lorentz–Lorenz approximation was used to correlate the excess molar volume from the deviation in refractive index and also to predict the density from refractive index or the refractive index from density of the binary mixtures. Four sound velocity mixing rules were tested and the best model for the systems studied in this work was the Berryman mixing rule. The thermodynamic properties are discussed in terms of intermolecular interactions between the components of the mixtures.     

Investigations of the reduced Redlich–Kister excess properties of 1,4-dioxane + isobutyric acid binary mixtures at temperatures from 295.15 to 313.15 K

Excess molar volumes and refractive index, molar refraction deviations and isentropic compressibility changes in 1,4-dioxane + isobutyric acid binary mixtures (from 295.15 to 313.15) K. were calculated from experimental density, refractive index and sound velocity data presented in previous work. Here, these experimental values were used to test the applicability of the correlative reduced Redlich–Kister equation as well as their corresponding relative functions which are important to reduce the effect of temperature and, consequently, to reveal the effects of different types of interactions. The results of these observations have been interpreted in terms of structural effects of the solvents. The correlating equation recently proposed by Belda, has also been applied to the present system in order to assess the validity of this equation and to give thermodynamic limiting partial molar quantities interesting to evaluate solute–solvent interaction.     

Densities, refractive indices and speeds of sound of the ternary mixtures (dimethyl carbonate + methanol + ethanol) and (dimethyl carbonate + methanol + 1-propanol) at T=298.15 K

Density, refractive index and speed of sound at T=298.15 K and atmospheric pressure have been measured over the entire composition range for (dimethyl carbonate (DMC) + methanol + ethanol) and (DMC + methanol + 1-propanol). Excess molar volumes, changes of refractive index on mixing and deviations in isentropic compressibility for the above systems have been calculated. The calculated quantities are further fitted to the Cibulka equation to estimate the ternary fitting parameters. Standard deviations from the regression lines are shown.     

Thermophysical properties of the ternary mixture ethanol + n-hexane + n-octane in function of the temperature

This article presents the analysis of the following physical properties such as refractive indices, excess molar volumes, sound velocity and the temperature dependence of the ternary system ethanol?+?n-hexane?+?n-octane in the temperature range 288.15–323.15?K at atmospheric pressure. The derived properties are calculated from data obtained experimentally and fitted to Cibulka equation.     

Thermophysical properties of the binary mixtures (1,8-cineole + 1-alkanol) at T = (298.15 and 313.15) K and at atmospheric pressure

This work presents the measurements of the density, speed of sound, refractive index and enthalpy of binary mixtures containing {1,8-cineole + 1-alkanol (ethanol, 1-propanol, 1-butanol, and 1-pentanol)} at two temperatures (298.15 and 313.15) K and atmospheric pressure. The determination of excess molar volume, speed of sound deviation, refractive index deviation, molar refraction, molar refraction deviation, excess isentropic compressibility, and excess molar enthalpy are also given. Redlich–Kister equation was used to fit these derivate properties. The experimental data of the constituent binaries were analysed to discuss the nature and strengths of intermolecular interactions. Eventually some models, SAFT and PC-SAFT for density, Free Length and Collision Factor for speed of sound, Gladstone-Dale Arago-Biot for refractive index, and UNIFAC for excess molar enthalpy, among others, were successfully applied.     

Temperature dependence of the properties of ternary systems ethanol + water + an aliphatic alkane (C6-C9)

The measures and calculation of different properties such as refractive index, density, speed of sound, excess molar volume, and isentropic compressibility of the ternary heterogeneous compounds by ethanol + water + (n-hexane, n-heptane, n-octane, n-nonane) have been performed in the range 288.15–323.15 K and atmospheric pressure. Attending to the accurate results of these models, the equation of state enclosing mixing rules is indicated as a simple estimation of the procedures of these properties for this kind of multicomponent systems.     

Study of molecular interactions in binary mixtures of formamide with 2-methoxyethanol and 2-ethoxyethanol at varying temperatures

The thermophysical properties of binary mixtures of formamide with 2-methoxyethanol and 2-ethoxyethanol have been investigated in this article. Densities, refractive index, ultrasonic velocity and viscosity for the two binary mixtures viz. formamide with 2-methoxyethanol and 2-ethoxyethanol have been measured over the entire composition range at 293, 303 and 313 K and at atmospheric pressure. The excess molar volume, the molar refraction deviation, excess Gibb's free energy of activation for viscous flow, excess isentropic compressibility, deviation in viscosity, excess free volume and excess molar enthalpy have been computed using experimental data. These excess parameters have been correlated with Redlich–Kister polynomial equation. The results have been interpreted on the basis of strength of intermolecular interaction occurring in these mixtures. Densities, refractive index and ultrasonic velocity were correlated with second-order polynomial equation. The molar volume and excess partial molar volume at infinite dilution have also been calculated for both the mixtures.     

Water density and polarizability deduced from the refractive index determined by interferometric measurements up to 250 MPa

The refractive index of water is precisely determined in the visible light range as a function of the pressure until 250 MPa by means of a new measurement device that uses a special pipe tee included in an interferometer set. This technique allows revisiting the Bradley-Tait and Sellmeier equations to make them dependent on the wavelength and the pressure, respectively. The Bradley-Tait equation for the pressure dependence of the water refractive index is completed by a wavelength-dependent factor. Also, in the considered pressure and wavelength ranges, it is shown that the Sellmeier coefficients can be straightforwardly linked to the pressure, allowing the determination of the refractive index of water for either any wavelength or pressure. A new simple model allows the determination of the density of water as a function of the measured refractive index. Finally, the polarizability of water as function of pressure and wavelength is calculated by means of the Lorentz-Lorenz equation.     

A new cubic equation of state for simple fluids: pure and mixture

A two-parameter cubic equation of state is developed. Both parameters are taken temperature dependent. Methods are also suggested to calculate the attraction parameter and the co-volume parameter of this new equation of state. For calculating the thermodynamic properties of a pure compound, this equation of state requires the critical temperature, the critical pressure and the Pitzer’s acentric factor of the component. Using this equation of state, the vapor pressure of pure compounds, especially near the critical point, and the bubble point pressure of binary mixtures are calculated accurately. The saturated liquid density of pure compounds and binary mixtures are also calculated quite accurately. The average of absolute deviations of the predicted vapor pressure, vapor volume and saturated liquid density of pure compounds are 1.18, 1.77 and 2.42%, respectively. Comparisons with other cubic equations of state for predicting some thermodynamic properties including second virial coefficients and thermal properties are given. Moreover, the capability of this equation of state for predicting the molar heat capacity of gases at constant pressure and the sound velocity in gases are also illustrated.     

Effect of the temperature on the physical properties of pure 1-propyl 3-methylimidazolium bis(trifluoromethylsulfonyl)imide and characterization of its binary mixtures with alcohols

In this paper, physical properties of a high purity sample of the ionic liquid 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [PMim][NTf₂], and its binary mixtures with methanol, ethanol, 1-propanol, and 2-propanol were measured at atmospheric pressure. The temperature dependence of density, refractive index and speed of sound (293.15 to 343.15) K and dynamic viscosity (298.15 to 343.15) K were studied at atmospheric pressure by conventional techniques for the pure ionic liquid. For its mixtures with alcohols, density, speed of sound, and refractive index were measured at T = 298.15 K over the whole composition range. The thermal expansion coefficient of the [PMim][NTf₂] was calculated from the experimental results using an empirical equation, and values of the excess molar volume, excess refractive index, and excess molar isentropic compressibility for the binary systems at the above mentioned temperature, were calculated and fitted to the Redlich–Kister equation. The heat capacity of the pure ionic liquid at T = 298.15 K was determined using DSC.     

Excess properties of binary mixtures hexane,heptane, octane and nonane with benzene,toluene and ethylbenzene at T = 283.15 and 298.15 K

Densities, speeds of sound and the refractive indices of binary systems containing alkanes (hexane, heptane, octane and nonane) with aromatic compounds (benzene, toluene and ethylbenzene) at T = 283.15 and 298.15 K under atmospheric pressure were determined over the whole composition range. From the experimental results, the derived and excess properties (excess molar volumes, isentropic compressibility, excess molar isentropic compressibility and refractive index deviations) at T = 283.15 and 298.15 K were calculated and satisfactorily fitted to the Redlich–Kister equation.     

Nonspherical ZnS colloidal building blocks for three-dimensional photonic crystals

The asymmetry introduced by a complex or nonspherical basis promotes photonic band gap formation in three-dimensional photonic crystals. However, relatively few techniques have been demonstrated to produce uniform nonspherical colloids for use as photonic crystal bases. Here we expand the menu of basis types with high refractive index by preparing nonspherical zinc sulfide colloids of uniform size and shape. Dimers, trimers, and planar tetramers were precipitated from aqueous solution by the thermal decomposition of thioacetamide in the presence of zinc nitrate, manganese nitrate, and nitric acid. The well-defined morphological types were obtained from suspensions aged for 4-6 h at 26-32 degrees C and then for 20-35 min at 85 degrees C. Stereological techniques were used to analyze SEM images and determine the percentage of each particle class. For example, the quantitative characterization of a particle population prepared at 29 degrees C for 6 h and 85 degrees C for 22 min had the composition 59+/-3% spheres, 31+/-2% dimers, 7+/-1% trimers, 0.4+/-0.2% tetramers, and 2.5+/-0.8% complex clusters (encompasses all other varieties of shape). X-ray diffraction and X-ray photoelectron spectroscopy confirmed the zinc blend crystal structure and the stoichiometric composition of the particles. The refractive index was estimated as 2.25 (413 nm) -2.09 (709 nm) by fitting experimental absorption spectra to curves derived from Mie scattering calculations. This indicated an average porosity approximately 24%. Such colloids offer the potential to form diamond-like lattices with large, stable photonic band gaps.     

New low-index liquid refractive index standard: SRM 1922

A new standard for the calibration of refractometers has been developed. Standard Reference Material (SRM) 1922 is a mineral oil with a refractive index nD = 1.46945 at 20 degrees C, which is within the range of the Brix scale (% sucrose). The change in refractive index with temperature (dn/dT) has been characterized for the range 15 degrees C to 35 degrees C to allow for calibrations within that range of temperatures. The refractive indices were measured at 5 wavelengths in the visible spectrum by using the method of minimum deviation with a +/- 2-3 x 10(-5) uncertainty at 20 degrees C. The values of nD and dnD/dT were determined by fits of a two-term Cauchy function to the values at the measured wavelengths with a +/- 6 x 10(-5) uncertainty in nD at 20 degrees C.     

Thermophysical properties of {(±)-linalool + propan-1-ol}: A first stage towards the development of a green process

In this paper, densities, speeds of sound and refractive indexes of binary mixture of {(±)-linalool (1) + propan-1-ol (2)} at four temperatures (283.15, 298.15, 313.15, and 328.15) K and 0.1 MPa are reported over the whole composition range. These data were used to calculate excess molar volume, speed of sound deviation, excess isentropic compressibility, refractive index deviation, molar refraction, and molar refraction deviation at the four work temperatures. All magnitudes were fitted to the Redlich–Kister equation. Subsequently prediction of speed of sound and refractive index was carried out using several theoretical models or equations. On the other hand, the density of the same mixture was determined in the same temperature range at pressures from 20 MPa to 40 MPa. Four equation of state (Peng–Robinson, Patel–Teja, SAFT, PC-SAFT) were tested as predictive models of the PρT behavior. The best results were obtained by PC-SAFT, with an average absolute deviation of 0.83%.     

Refractive index of thin, aqueous films between hydrophobic surfaces studied using evanescent wave atomic force microscopy

We have studied the refractive index of a thin aqueous film between microscopic hydrophobic surfaces using evanescent wave atomic force microscopy (EW-AFM). An evanescent wave, generated at a solid-liquid interface, is scattered by AFM tips or glass particles attached to AFM cantilevers. The scattering of this wave is used to determine the refractive index as a function of separation between these surfaces. Measurements were performed on surfaces that were rendered hydrophobic with octadecyltrichlorosilane, which produces solid-water contact angles in excess of 90 degrees. For AFM tips, the average refractive index in the thin film was always equal to that of water when the film was thicker than approximately 100 nm. At smaller separations, the refractive index was always greater than or equal to that of water. This is inconsistent with the formation of air or vapor films and consistent with a small amount of organic material between the surfaces. For colloidal spheres (R approximately 10 microm), we were not able to detect changes in the refractive index of the thin film between the sphere and plate.     

Equation of state of water under negative pressure

We report on the simultaneous measurements of the speed of sound and the density in liquid water under negative pressure. Application of a focused acoustic wave to the bulk liquid is able to generate negative pressures before nucleation of the vapor phase occurs. A method for time-resolved Brillouin scattering is developed to measure the speed of sound during the passage of a 1 MHz ultrasonic wave. This is coupled with a fiber optic probe hydrophone which allows the determination of the density. Together, these methods give an ambient temperature equation of state of metastable liquid water down to the acoustic cavitation threshold. Empirical equations of state of water are based on experimental data at positive pressure; the validity of their extrapolation to negative pressures had been tested only indirectly or with very weakly metastable liquid. We provide thermodynamic data that prove the fidelity of recent equations of state down to -26 MPa. However, this raises questions regarding the nature of the cavitation threshold observed in acoustic experiments, which is far less negative than expected.     

傅里叶变换表面等离子体共振频率对金膜表面溶液折射率响应

采用新型傅里叶变换表面等离子体共振仪（FT-SPR）,测定了NaCl、KCl和乙醇3种水溶液在不同浓度下的SPR响应值,建立了SPR响应与溶液浓度和折射率之间的定量关系R=1.53×105(n -1.3333),测定了FT-SPR 100型仪器的折射率响应常数m=1.53×105,即液体折射率每变化0.000 1,FT-SPR响应值变化为15 cm-1。 其结果为用FT-SPR直接测定液体样品的折射率提供了可能。     

Equation of state for expanded fluid mercury: variational theory with many-body interaction

A variational associating fluid theory is proposed to describe equations of state for expanded fluid mercury. The theory is based on the soft-sphere variational theory, incorporating an ab initio diatomic potential and an attractive many-body potential; the latter is evaluated with quantum chemical methods and expressed as a function of the local atomic coordination number and the nearest-neighbor distance. The resultant equation of state can reproduce the observed gas-liquid coexistence curve with good accuracy, without introducing phenomenological effective pair potentials. Various thermodynamic quantities such as pressure, isocloric thermal pressure coefficient, adiabatic sound velocity, and specific heat are calculated over a wide density-temperature range and compared with available experimental data.