Vibrating-tube Density Meter Research Articles

P[formula omitted]T measurements of Glycols (Mono-, Di- and Triethylene glycol) up to 423.15 K and 140.0 MPa and their aqueous solutions at atmospheric pressure

The density of three glycols, namely Monoethylene glycol (MEG), Diethylene glycol (DEG), and Triethylene glycol (TEG) was measured in the temperature range from 298.15 K to 423.15 K and pressures up to 140.0 MPa using a vibrating tube density meter Anton Paar DMA-HPM, coupled with a high-pressure mPDS 5 unit. The modified Tait-Tammann equation was used to correlate the experimental density, which gave an absolute average relative deviation (AARD) of less than 0.2 %. Derived properties such as isobaric thermal expansion and isothermal compressibility coefficients were estimated and discussed. Furthermore, the density of the binary systems composed by the aforementioned glycols (1) + water (2) was also measured in the (273.15, 373.15) K temperature range at atmospheric pressure. The Cubic-Plus-Association (CPA) and the simplified version of the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equations of state were used to correlate the newly measured data, with deviations less than 3.7 % for pure component and 12.0 % for the binary systems.

Density, Excess Molar Volume and Vapor–Liquid Equilibrium Measurements at 101.3 kPa for Binary Mixtures Containing Ethyl Acetate and a Branched Alkane: Experimental Data and Modeling

Vapor–liquid equilibrium (VLE) and density data for binary systems of branched alkanes + ethyl acetate are scarce in the literature. In this study, the binary mixtures 3-methylpentane + ethyl acetate and 2,3-dimethylbutane + ethyl acetate were investigated. Density measurements at atmospheric pressure were performed using a vibrating tube density meter at 293.15, 298.15 and 303.15 K. Large and positive excess molar volumes were calculated and correlated using a Redlich–Kister-type equation. Isobaric VLE data at 101.3 kPa were obtained using a Gillespie-type recirculation ebulliometer. Equilibrium compositions were determined indirectly from density measurements. The experimental data were checked for consistency by means of the Fredenslund test and the Wisniak (L-W) test and were then successfully correlated using the NRTL model. The newly studied binary systems display high deviations from ideality and minimum boiling azeotropes, the coordinates of which are reported in this work.

An investigation on the thermophysical properties of glycerol

A vibrating tube density meter (VTD) was used to measure density of pure glycerol at different isotherms between 298.16 and 423.12 K, and a pressure range up to 55 MPa. The VTD was calibrated based on the measurements conducted for water and nitrogen. Speed of sound in glycerol was also obtained by mean of a double path acoustic technique in a high pressure acoustic cell. Speed of sound measurements were conducted at five isotherms between 298.14 and 398.16 K with pressures limited to 55 MPa. The acoustic cell was calibrated with distilled water. Validation tests were performed by measuring the density and sound velocity in pure toluene using the VTD and acoustic cell, respectively. The maximum uncertainty (with 95 % level of confidence, k = 2) of the measured densities and sound velocities were found to be 1.27 kg.m−3 and 4.07 m.s−1, respectively.In addition, the measured sound velocities combined with some reliable literature data for density, heat capacity and sound velocity at atmospheric pressure were utilised to determine density, isobaric, and isochoric heat capacities and the Joule-Thomson coefficient using a numerical integration method. Finally, the calculated densities were compared with measured densities from this work and literature, and a good agreement was observed.

Density and sound velocity measurement by an Anton Paar DSA 5000 density meter: Precision and long-time stability

Vibrating tube density meters are frequently used in routine measurements. The instruments are often equiped with a cell for sound velocity measurement. The methodology of measurement is described in the operation manual and many papers contain recommedations how to achieve data with higher precision. This work is aimed to the study of importance of each aspect of the measurement procedures, effects of neglection of a viscosity correction as well as the magnitude of induced errors. Numerical values of all effects are presented. As a result of thorough analysis not yet published recommendations for best practice of density and sound velocity measurements are summarized.

Densities and excess volumes of aqueous monoethanolamine and diisopropanolamine systems at atmospheric pressure from 303.15 K to 333.15 K

The densities of water+monoethanolamine (MEA), water+diisopropanolamine (DIPA), DIPA+MEA binary systems and water+DIPA+MEA ternary system were measured over the full range of composition at temperatures from 303.15 K to 333.15 K by using an Anton Paar digital vibrating tube density meter (DMA4500). The experimental excess volumes were obtained from the experimental density results and fitted using the Redlich-Kister-Muggianu expression. The parameters obtained from the binary excess volume data were used for the correlation of ternary system with one additional ternary parameter for each isotherm. All investigated binary and ternary systems are completely miscible, because the values of excess volume are negative under the examined conditions.

Excess specific volume of water + tert-butyl alcohol solvent mixtures: Experimental data, modeling and derived excess partial specific thermodynamic quantities

The aim of this work is to develop a model for the dependence of the excess specific volume of the water + tert-butyl alcohol system on both composition and temperature under the temperature and pressure conditions relevant to the manufacturing and processing of poorly water-soluble drug formulations intended to be freeze-dried. For this purpose, experimental excess volumes of binary solvent mixtures were obtained from density measurements performed with a vibrating-tube density meter and carried out at atmospheric pressure for thirty-nine compositions covering the whole composition range and at five temperatures over the range from 293.15 to 313.15 K. For every temperature investigated, experimental excess volume data were fitted by a Redlich-Kister-based equation. By considering the temperature dependence of the regression coefficient estimates thus determined, the complete model equation was obtained and further validated by testing its correlative and predictive capabilities against data from this work and those from literature, respectively. Then, it was used to derive expressions for the excess partial thermodynamic quantities and their variations with respect to composition and temperature were discussed in terms of molecular interactions and structural arrangements in solution.

Volumetric behavior of carbon dioxide + 2-methyl-1-propanol and carbon dioxide + 2-methyl-2-propanol mixtures at 313.15 K

Volumetric properties were measured of carbon dioxide+2-methyl-1-propanol and carbon dioxide+2-methyl-2-propanol mixtures at 313.15K, using the vibrating tube density meter. In the present experiments, no analytical instrument was required. The saturated pressure was also measured of carbon dioxide+2-methyl-1-propanol and carbon dioxide+2-methyl-2-propanol mixtures at 313.15K by the synthetic method. The experimental data obtained were correlated with the density equation, Soave–Redlich–Kwong (SRK) equation of state, and the pseudocubic equation of state. The partial molar volumes of carbon dioxide and C4 alcohols (2-methyl-1-propanol or 2-methyl-2-propanol) were calculated, based on the calculated results by the density equation.

Densities of a deep eutectic solvent based on choline chloride and glycerol and its aqueous mixtures at elevated pressures

Deep eutectic solvents are cheap and biodegradable alternatives to conventional ionic liquids and volatile organic solvents. In this work, we present new measurements on the densities of the deep eutectic solvent choline chloride:glycerol (GLY) and its aqueous mixtures in the temperature range (298.15–323.15)K and pressures up to 50MPa. The density was measured using a vibrating-tube density meter and the experimental uncertainty was estimated to be ±0.1%. Density data were used to derive other properties such as isothermal compressibility, isobaric expansivity, and excess molar volume. The excess molar volumes of the mixtures of GLY (1)+H2O (2) were investigated and an empirical equation was used to represent their dependence on temperature, pressure, and composition. The density data at elevated pressures were correlated with the temperature, pressure, and composition by a Tait-type equation.

Volumetric Behavior of Carbon Dioxide + Butan-1-ol Mixtures at 313.15 K

Volumetric behavior was measured of carbon dioxide + butan-1-ol mixtures at 313.15 K using a vibrating tube density meter. The saturated pressures were also measured of carbon dioxide + butan-1-ol mixtures at 313.15 K by the conventional synthetic method. The equilibrium vapor compositions were newly evaluated by combining the molar volume equation, the experimental values of the equilibrium vapor density, vapor density of pure carbon dioxide, and pressure.

Experimental Study on the Surface Tension, Density, and Viscosity of Aqueous Poly(vinylpyrrolidone) Solutions

Aqueous solutions of the polymer poly(vinylpyrrolidone) (PVP) were analyzed in terms of surface tension (Wilhelmy-Plate), density (vibrating tube density meter), and dynamic viscosity (falling ball viscometer) for different molar masses, concentrations, and temperatures. Surface tensions were determined for PVP 10, K25, and K90 at 298.15 K. Densities and viscosities were studied with PVP K25 and K90 in a temperature region from (293.15 to 310.15) K. The dynamic viscosity isotherms were fitted successfully to a basic polynomial function. The experimental data are discussed and compared to literature data.

High pressure vapor–liquid equilibria for carbon dioxide + tetrahydrofuran mixtures

Vapor–liquid equilibria and saturated density for carbon dioxide + tetrahydrofuran mixtures at high pressures were measured by the analytical method at the temperatures 298.15 and 313.15 K. The experimental apparatus equipped with three Anton Paar DMA 512S vibrating tube density meters was previously developed for measuring vapor–liquid–liquid equilibrium at high pressures. The equilibrium composition and saturated density of each phase were determined by gas chromatograph and vibrating tube density meters, respectively. The bubble point pressure at the temperature 313.15 K was further measured by the synthetic method. The experimental data were correlated with Soave–Redlich–Kwong (SRK) equation of state and the pseudocubic equation of state.

High-Pressure Vapor−Liquid Equilibrium for Ethylene + 2-Methyl-1-propanol

Vapor−liquid equilibria and the saturated density for the ethylene + 2-methyl-1-propanol system at high pressures were measured at the temperatures (278.15, 283.65, and 288.15) K with a static-circulation apparatus. The experimental apparatus equipped with three Anton Paar DMA 512S vibrating-tube density meters was previously developed for measuring vapor−liquid−liquid equilibrium at high pressures. Coexisting phase composition and saturated density of each phase can be measured by means of the apparatus with a maximum temperature and pressure of 400 K and 20 MPa, respectively. The equilibrium composition and saturated density of each phase were determined by gas chromatography and vibrating-tube density meters, respectively. The experimental data were correlated with various equations of state.

A Comprehensive Model for Packing and Hydration for Amyloid Fibrils of β2-Microglobulin

Volume can provide informative structural descriptions of macromolecules such as proteins in solution because a final volumetric outcome accompanies the exquisite equipoise of packing effects between residues, and residues and waters inside and outside proteins. Here we performed systematic investigations on the volumetric nature of the amyloidogenic conformations of beta2-microglobulin (beta2-m) and its amyloidogenic core peptide, K3, using a high precision densitometer. The transition from the acid-denatured beta2-m to the mature amyloid fibrils was accompanied by a positive change in the partial specific volume, which was larger than that observed for the transition from the acid-denatured beta2-m to the native structure. The data imply that the mature amyloid fibrils are more voluminous than the native structure because of a sparse packing density of side chains. In contrast, the formation of the mature amyloid-like fibrils of the K3 from the random coil was followed by a considerable decrease in the partial specific volume, suggesting a highly compact core structure. Interestingly, the immature amyloid-like fibrils of beta2-m exhibited a volume intermediate between those of the mature fibrils of beta2-m and K3, because of the core structure at their center and the relatively noncompact region around the core with much hydration. These volumetric differences would result from the nature of main-chain-dominated fibrillogenesis. We suggest comprehensive models for these three types of fibrils illustrating packing and hydrational states.

Densities, Viscosities, Refractive Indices, and Surface Tensions for the Ternary Mixtures of 2-Propanol + Benzyl Alcohol + 2-Phenylethanol at T = 308.15 K

Densities, viscosities, refractive indices, and surface tensions for the ternary system of 2-propanol + benzyl alcohol + 2-phenylethanol were measured at T = 308.15 K and atmospheric pressure. Densities were determined using a vibrating-tube density meter. Viscosities were measured with an automatic Ubbelholde capillary viscometer. Refractive indices were measured using a digital Abbe-type refractometer. Surface tensions were determined by the Wilhelmy-plate method. The experimental data are used to calculate excess molar volumes VE, deviations in the viscosity Δη, deviations in the refractive index ΔnD, and deviations in the surface tension Δσ. The calculated quantities VE, Δη, ΔnD, and Δσ were fitted to the variable-degree polynomials.

Densities and Viscosities of N,N-Dimethylformamide + Formic Acid, and + Acetic Acid in the Temperature Range from (303.15 to 353.15) K

Densities and viscosities for formic acid and acetic acid with dimethylformamide (DMF) were determined at atmospheric pressure from (303.15 to 353.15) K. The measurements were carried out over the whole range of compositions, using a vibrating-tube density meter and an Ubbelohde viscometer. The density and viscosity measurements were used to compute the excess molar volumes, VE, and viscosity deviations, Δη. The excess molar volumes and viscosity deviations have been fit to the Redlich−Kister equation.

Volumetric Properties and Viscosities of Binary Mixtures of N,N-Dimethylformamide with Methanol and Ethanol in the Temperature Range (293.15 to 333.15) K

Densities and viscosities of the binary mixtures of methanol + DMF and ethanol + DMF have been measured over several temperatures at atmospheric pressure. The measurements were carried out over the whole range of compositions, using a vibrating-tube density meter and an Ubbelohde viscometer. The densities are used to calculate excess molar volumes for each of the systems. The experimental values of excess molar volumes have been compared with those reported by other authors available in the literature. The Redlich–Kister equation was fitted to excess molar volumes, VE, and viscosities, η.

Experimental setup to measure critical properties of pure and binary mixtures and their densities at different pressures and temperatures: Determination of the precision and uncertainty in the results

We describe an experimental setup to measure critical properties and density as a function of pressure and temperature. Critical temperature and critical pressure ( T c, P c) are measured with a flow apparatus, and detected by critical opalescence. Precision in measuring critical points for pure compounds and binary mixtures are characterized in terms of repeatability and confidence interval. The volumetric properties are determined with a high-pressure vibrating-tube density meter, calibrated from 278.15 to 318.15 K at pressures up to 200 × 10 5 Pa. Density values are validated for pure compounds by determining the absolute and relative root-mean-square deviations to CO 2 data obtained from the Span and Wagner equations of state (EOS), and for binary mixtures by determining the relative mean standard deviation of density, s ¯ ρ r . Both the critical and volumetric experimental results have been compared with literature data and values obtained from the Peng–Robinson and Patel–Teja cubical equations of state.

High-pressure phase equilibrium for ethylene + 1-butanol at 283.65 K and 290.80 K

Phase equilibria and saturated densities for ethylene + 1-butanol at high pressures are measured at the temperatures 283.65 K and 290.80 K with a static-circulation apparatus including the vicinity of the critical region. The equilibrium composition and saturated density of each phase are determined by using gas chromatograph and vibrating tube density meters, respectively. The present experimental results include VLE, LLE, and VLLE with density data at the temperature 283.65 K. The saturated points near the critical region at the temperature 283.65 K are further measured by the conventional indirect method using the variable volume apparatus. The experimental data are correlated with Soave–Redlich–Kwong (SRK) equation of state and the pseudocubic equation of state.

Densities, Viscosities, Refractive Indexes, and Surface Tensions for Binary Mixtures of 2-Propanol + Benzyl Alcohol, + 2-Phenylethanol and Benzyl Alcohol + 2-Phenylethanol at T = (298.15, 308.15, and 318.15) K

Densities, viscosities, refractive indexes, and surface tensions for three binary systems (2-propanol + benzyl alcohol, 2-propanol + 2-phenylethanol, and benzyl alcohol + 2-phenylethanol) were measured at T = (298.15, 308.15, and 318.15) K over the whole composition range at atmospheric pressure. Densities were determined using a vibrating-tube density meter. Viscosities were measured with an automatic Ubbelholde capillary viscometer. Refractive indexes were measured using a digital Abbe-type refractometer. Surface tensions were determined by the Wilhelmy-plate method. These results are used to calculate excess molar volumes, , deviations in the viscosity, Δη, deviations in the refractive index, ΔnD, and the deviations in the surface tension, Δσ, at these three temperatures. The calculated quantities of , Δη, ΔnD, and Δσ were fitted to the Redlich−Kister equation to estimate the binary interaction parameters.

Vapor–liquid equilibrium, densities and viscosities for the binary system exo- and endo-tetrahydrodicyclopentadiene and pure component vapor pressures

Vapor pressures of exo- and endo-tetrahydrodicyclopentadiene (THDCPD) were measured by using dynamic glass still at T = 335–463 K. The experimental vapor pressures were fitted well with the Antoine equation. Isobaric vapor–liquid equilibria for the binary system exo-THDCPD + endo-THDCPD were determined by a using dynamic method at six constant pressures of 10, 30, 50, 70, 90 and 101.3 kPa. All the VLE data sets were correlated with NRTL model. Additionally, densities and viscosities at 288.15, 298.15, 308.15 and 318.15 K for the same binary mixtures were measured by using a vibrating tube density meter and a precision viscometer, respectively.