Temperature In Binary Mixtures Research Articles

Viscosities and Densities of Binary and Ternary Mixtures of Aliphatic and Polyaromatic Hydrocarbons: Pyrene +1-Methylnaphthalene + Dodecane at T = (293.15 to 343.15) K. Experiment and Modeling.

This work presents new experimental viscosity and density data for aromatic and polyaromatic compounds in binary and ternary pyrene, 1-methylnaphthalene, and dodecane mixtures. The lack of experimental viscosity data for these mixtures requires the development of a new database, which is vital for understanding the behavior of mixtures in more complex systems, such as asphaltenes and fuels. The mixtures proposed in this work have been measured over a temperature range of (293.15 to 343.15) K at atmospheric pressure. Several mixture compositions have been studied at these conditions: 1.0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0% pyrene mass fraction. The concentration of pyrene correlates with an increase in the viscosity and density values. At the lowest temperature in binary mixtures, the corresponding values reach 4.4217 mPa·s for viscosity and 1.0447 × 103 kg·m-3 for density, respectively. In ternary mixtures, the introduction of dodecane leads to the lowest maximum values of 3.5555 mPa·s for viscosity and 1.0112 × 103 kg·m-3 for density at the same temperature. The experimental data have been employed for the specific modification of viscosity models. These modifications could facilitate the prediction of the viscosity of mixtures that are more complex than those presented in this work. Various viscosity models have been employed, such as Linear, Ratcliff and Khan, modified UNIFAC-Visco, and Krieger-Dougherty. The settings in the models used reliably reproduce the experiment reliably. However, the Ratcliff model agrees excellently with the experiment, having a low standard deviation (2.0%) compared to other models. Furthermore, a model based on the equation of state of Guo is proposed to predict the viscosity values by modifying the specific parameters and adjusting them to the mixtures proposed in this work. The results from this study are compared to previous work, where pyrene, toluene, and heptane mixtures were analyzed. In this case, we find that the decrease of aggregation grade in the present systems is predicted by the model fixed in this work.

How does pressure affect the molecular dynamics, intramolecular interactions, and the relationship between structural (α) and secondary (JG-β) relaxation above and below the glass transition temperature in binary mixtures of H-bonded API – probucol and acetylated saccharides?

In this paper, the molecular dynamics as well as inter- and intramolecular interactions in the homogenous solid dispersions (SDs) of active pharmaceutical ingredient - probucol (PRO) with acetylated glucose (acGLU), acetylated sucrose (acSUC), and sucrose acetoisobutyrate (aibSUC), prepared in 5:1 molar ratio, have been investigated using broadband dielectric (BD) and Fourier transform infrared (FTIR) spectroscopy. Importantly, high pressure dielectric measurements revealed that as for neat PRO, a breakdown of the isochronal structural (α) and JG-β exact superpositioning, due to increasing separation between both processes under compression, can also be detected in its mixtures with acetylated saccharides (acSACCHs). Furthermore, the analysis of temperature dependences of JG-β-relaxation times for PRO and PRO-acSACCH SDs at selected isobaric conditions indicated the increase in the cooperativity of the secondary process (reflected in the value of the activation entropy, ΔSβ) at elevated pressure in all systems. The mere addition of the small amount of excipient to neat PRO (p = 0.1 MPa) resulted in a greater value of ΔSβ (it was the most noticeable in the case of aibSUC). Further FTIR studies carried out on the pressure densified glasses of PRO, and binary mixtures suggested that the observed changes in the cooperativity of the JG-β-process, as well as the failure of the exact isochronal superpositioning of α- and JG-β relaxation times, are due to varying H-bond pattern in the examined single- and two-component systems at high compression/in the presence of saccharide.

Visual Measurements of Solid–Liquid Equilibria and Induction Times for Cyclohexane + Octadecane Mixtures at Pressures to 5 MPa

A specialized apparatus designed for visual measurements of solid–liquid equilibrium (SLE) and solid–liquid–vapor equilibrium (SLVE) was constructed and used to measure liquidus (melting) temperatures in binary mixtures of cyclohexane (C6H12) and octadecane (C18H38) across the entire range of composition and at pressures from about (0.004 to 5.3) MPa. A Peltier-cooled copper tip immersed in the liquid mixture was used to determine both freezing and melting temperatures by varying the temperature of the copper tip relative to the stirred, bulk liquid. With the bulk liquid held at the mixture’s SLVE temperature, the induction time required to nucleate solid octadecane decreased exponentially as the subcooling of the copper tip increased, halving approximately every 0.25 K. At higher pressures, while the melting temperature of pure cyclohexane (cyC6) increased by about 0.55 K·MPa–1, at xcyC6 = 0.5675 it increased by only 0.15 K·MPa–1. The new data were compared with measurements reported in the literature, e...

The thermal storage performance of mixtures consisting of liquid paraffin and fatty acids

ABSTRACTThe thermal storage performance of binary mixtures consisting of fatty acids and liquid paraffin (LP) was studied experimentally. The study is to look for the material with suitable phase transition temperature and high phase change latent heat. The phase transition temperatures of binary mixtures consisting of capric acid and other four kinds of fatty acid are between 20°C and 30°C, and the phase change latent heat is high. They are ideal phase change materials used in the wall. The binary mixtures consisting of stearic acid, palmitic acid, lauric acid (LA) and myristic acid have high phase transition temperatures, and they are not suitable to use in the wall. The phase transition temperatures of mixtures consisting of LP and LA are between 20°C and 30°C, and the phase change latent heat is high. They can be used in the wall. The thermal stability of fatty binary mixtures is good.

Effect of ferroelectric liquid crystalline quaterphenyl structure and handedness on helical pitch length in bicomponent mixtures

ABSTRACTThe aim of this paper is characterisation of mesomorphic properties and helical structure parameters: handedness and helical pitch, of two laterally substituted ferroelectric compounds and mixtures based on them. These compounds have the same quaterphenyl rigid core and the same length of non-chiral chain – eight carbon atoms, as well as the absolute configuration of chiral centre (‘R’). Base compounds differ in the kind of a substituent in a rigid core (–Cl, –CH3). Both of them have rather low melting temperature in comparison to most of quaterphenyls, and it affects the lowering of this temperature in binary mixtures. Thus they can be used for preparation of multicomponent ferroelectric mixtures useful for application.

The Second Mode in High-enthalpy Boundary Layers in Chemical Non-equilibrium

Boundary layers at a zero pressure gradient in chemical non-equilibrium are considered for a five-species model of air in a total enthalpy range of 5 - 17MJ/kg. Comparisons with boundary layers in binary mixtures of oxygen reveal that the growth rates of the second mode are lower in the case of air. This result can be attributed to the lower wall temperatures in binary mixtures of oxygen due to dissociation, with the lower wall temperatures having a destabilizing effect on the second mode similar to the case of boundary layers in calorically perfect gases.

Determination of Latent Mesogenic Behavior in Nonmesogenic Compounds by Extrapolation Method

A homologous series of 8-(4′-n-alkoxybenzoyloxy) quinolines were synthesized by established methods [5,6]. On evaluation by optical microscopy, none of the homologues were found to exhibit mesogenic behavior even in the monotropic condition. Then, each homologue (B) was mixed with a liquid crystal component (A) and binary systems were studied by optical microscopy. Solid–mesomorphic or isotropic–nematic transition temperatures of binary mixtures were determined and plotted to obtain the phase diagram for transition temperatures versus percentage composition of component (A). The nematic–isotropic transition curve was extrapolated to zero mole percentage of component (A) (100%B) to determine the latent transition temperature (LTT) of each nonmesomorphic homologue. The number of carbon atoms in the n-alkyl chain of each homologue versus LTT is plotted and a phase diagram is obtained. The isotropic–nematic transition curve behaves in a normal manner like a curve behaving for a typical nematogenic homologous series, including odd–even effects in its phase diagram. This method is useful to determine the probable temperature at which a nonmesogenic substance can show mesogenic behavior, provided a suitable condition is applied. Also, it is useful to correct the LTT of a homologue from the mesomorphic–isotropic transition curve.

Nematic–isotropic phase transition of binary liquid crystal mixtures

We experimentally studied the nematic–isotropic phase transition of (a) binary mixtures consisting of nematic and racemic liquid crystals and (b) binary mixtures consisting of positive and negative dielectric liquid crystals. We observed that the phase transition temperature is very sensitive to the chemical structures of the constituent components. We also used Maier–Saupe theory to calculate the transition temperature of binary mixtures. By fitting the experimental data, we obtained the interaction coupling constant between the constituent components.

Phase Equilibria of an Ammonium Ionic Liquid with Organic Solvents and Water

We report the phase diagrams of an ammonium ionic liquid: (benzyl)dimethylalkylammonium nitrate, [BA][NO3], where the alkyl is {C12H25 (w = 0.4) or C14H29 (w = 0.6)} with alcohols (propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, and decan-1-ol); with hydrocarbons (benzene, toluene, hexane, and hexadecane); and with water. The phase equilibria were measured by a synthetic method from 220 K to the melting point of the ionic liquid or to the normal boiling temperature of the solvent. Simple eutectic systems were observed for binary mixtures of [BA][NO3] with propan-1-ol and with butan-1-ol. The solid−liquid equilibria with immiscibility in the liquid phase for the ([BA][NO3] + water, hexan-1-ol, octan-1-ol, decan-1-ol, benzene, toluene, hexane, or hexadecane) are described. The difference of the solubility of the ionic liquid with longer chain alcohols is significant, a simple eutectic system was observed with immiscibility in the liquid phase for low mass fraction of the solvent. The upper critical solution temperature in binary mixtures of {[BA][NO3] + heptane or hexadecane} was limited by the boiling temperature of the solvent. For the systems evaluated, immiscibility of the liquid mixtures was observed up to a very high mass fraction of the ionic liquid.

Phase equilibria of didecyldimethylammonium nitrate ionic liquid with water and organic solvents

The phase diagrams for binary mixtures of an ammonium ionic liquid, didecyldimethylammonium nitrate, [DDA][NO 3], with: alcohols (propan-1-ol, butan-1-ol, octan-1-ol, and decan-1-ol): hydrocarbons (toluene, propylbenzene, hexane, and hexadecane) and with water were determined in our laboratory. The phase equilibria were measured by a dynamic method from T = 220 K to either the melting point of the ionic liquid, or to the boiling point of the solvent. A simple liquidus curve in a eutectic system was observed for [DDA][NO 3] with: alcohols (propan-1-ol, butan-1-ol, and octan-1-ol); aromatic hydrocarbons (toluene and propylbenzene) and with water. (Solid + liquid) equilibria with immiscibility in the liquid phase were detected with the aliphatic hydrocarbons heptane and hexadecane and with decan-1-ol. (Liquid + liquid) equilibria for the system [DDA][NO 3] with hexadecane was observed for the whole mole fraction range of the ionic liquid. The observation of the upper critical solution temperature in binary mixtures of ([DDA][NO 3] + decan-1-ol, heptane, or hexadecane) was limited by the boiling temperature of the solvent. Characterisation and purity of the compounds were determined by elemental analysis, water content (Fisher method) and differential scanning microcalorimetry (d.s.c.) analysis. The d.s.c. method of analysis was used to determine melting temperatures and enthalpies of fusion. The thermal stability of the ionic liquid was resolved by the thermogravimetric technique–differential thermal analysis (TG–DTA) technique over a wide temperature range from (200 to 780) K. The thermal decomposition temperature of 50% of the sample was greater than 500 K. The (solid + liquid) phase equilibria, curves were correlated by means of different G Ex models utilizing parameters derived from the (solid + liquid) equilibrium. The root-mean-square deviations of the solubility temperatures for all calculated data are dependent upon the particular system and the particular equation used. Comparison of the solubilities of different ammonium salts in alcohols, in hexane, in benzene, and in water are discussed.

Solvent effect on lipase enantioselectivity. Evidence for the presence of two thermodynamic states.

The enantioselectivity of lipase-catalyzed kinetic resolutions has been measured at various temperatures in binary mixtures of solvents. Varying the solvent composition and temperature had a profound effect on the enantiomeric ratio. The values for delta delta H(R-S)(#) and delta delta S(R-S)(#), calculated from the E values measured at various temperatures, were estimated as a function of the solvent composition. By plotting delta delta H(R-S)(#) versus delta delta S(R-S)(#) as a function of the solvent composition, an extreme was observed. The resulting "hairpin-type" enthalpy-entropy compensation plots can be described by assuming the presence of two thermodynamically distinct physical states, displaying different enantioselectivities, that are in equilibrium with one another. Changing the solvent composition results in a change in the equilibrium constant K(eq) for the two states. The intriguing bell-shaped curves of the enantioselectivity versus solvent composition observed for lipase-catalyzed kinetic resolutions can be described assuming a linear correlation for the logarithm of K(eq) and the solvent composition. Thus, a simulation of the two-state model adequately describes the solvent effects found for lipase-catalyzed kinetic resolutions in binary mixtures of solvents and possibly in series of homologous organic solvents.

Effect of molecular structure on the phase behaviour of some liquid crystalline compounds and their binary mixtures IV. Dependence of Tc on the anisotropy of the aryl-X of polarizability bond

Transition temperatures of binary mixtures of the two series, 4-hexadecyloxyphenyl-4- substituted benzoates (Ia-d) and 4-substituted phenyl-4-hexadecyloxybenzoates (IIa-d), have been determined on cooling and the phase diagrams compared with those previously obtained on heating. Tc values for the monotropes and the non-LC analogues have been evaluated by extrapolation. Examination of both series revealed that the square root of Tc is related to the polarizability anisotropy, Delta alphaX, of the CAr-X bond, except for the methoxy derivatives.

Temperature flammability limits and fire temperatures for binary mixtures of linear hydrocarbons

Temperature flammability limits and fire temperatures for binary mixtures of linear hydrocarbons

Excess thermodynamic properties of mixtures of alkyl benzoates withn-heptane

The paper reportshE values at 298.15 K andvE and δη values at various temperatures for binary mixtures of propyl or butyl benzoate andn-heptane. The excess Gibbs energy of viscous flow,Δg*E, and the thermodynamic activation properties were calculated from these values. The results are compared with those for similar mixtures and interpreted on the basis of the characteristic dipole-dipole interactions of alkyl esters.

Unusual critical temperature phenomena in fluid mixtures containing perfluorotributylamine

Abstract Sadus, R.J., 1992. Unusual critical temperature phenomena in fluid mixtures containing perfluorotributylamine. Fluid Phase Equilibria , 77: 269-283. The critical temperatures of binary mixtures containing perfluorotributylamine and a hydrocarbon are calculated and compared with experimental data. Systems containing low molecular weight hydrocarbons exhibit a positive deviation from linearity whereas a temperature minimum is reported for mixtures containing a higher molecular weight alkane. Between these extremes some mixtures display both a temperature minimum and a positive deviation. Theory can qualitatively reproduce this phenomenon. The calculations using an optimized value of the combining rule adjustable parameter (ξ) yield good results whereas calculations with the van der Waals prescription (ξ = 1) do not predict the behaviour. Better results are obtained using a theoretical alternative to mixture prescriptions for the attractive equation of state parameter. The critical temperatures of some ternary perfluorotributyl-amine + hydrocarbon mixtures are also reported. The anomalous behaviour is also observed in the ternary systems. The critical conditions for a ternary mixture are solved. The comparison between theory and experiment indicates that the temperature minimum of these ternary mixtures can be predicted but a positive deviation is not observed.

Changes of the physical properties of the liquid-ordered phase with temperature in binary mixtures of DPPC with cholesterol: A 2H-NMR, FT-IR, DSC, and neutron scattering study

The structure of the so-called liquid-ordered (lo) phase of binary mixtures of DPPC-d(62) with cholesterol was studied between 20-50 mol% cholesterol using (2)H-NMR, FT-IR, DSC, and neutron specular reflection. Different model systems such as multilamellar vesicles, spherical supported vesicles, and oriented multilayers were used. We observed significant changes of the lo phase structure in the physiological relevant temperature region between 30-45 degrees C. (2)H-NMR in combination with lineshape simulations provides evidence for a drastic effect of cholesterol on the shape of multilamellar vesicles due to magnetic field orientation. Moreover, the data indicates a significant change of the extent of this partial orientation for DPPC-d(62) multilamellar vesicles containing 25 mol% cholesterol between 36-42 degrees C. The semiaxes ratio of the (due to magnetic field orientation) ellipsoidal multilamellar vesicles changes over this temperature range by approximately 25%. (2)H-NMR and FT-IR measurements indicate changes of the average orientational order at the bilayer center in the same temperature range and a significant increase of the number of end-gauche conformers while the majority of the methylene groups remain in an all-trans conformation. Additionally, specular reflection of neutrons shows a concomitant reduction of the bilayer thickness by 4 A. Based on a model of the arrangement of DPPC and cholesterol in the lo phase, a molecular mechanism is proposed in which increasing the temperature between 30 and 45 degrees C has the effect of driving cholesterol from the bilayer center towards the head group region.

Solubility ofp-phenylazophenol in low molecular weight liquid crystalline precursors

Freezing point temperatures for binary mixtures containing phenylazophenol (PAP) with p-(p-methoxyphenylazo)phenol (MOPAP), p-(p-ethylphenylazo)phenol (EPAP) and p-(p-ethoxyphenylazo)phenol (EOPAP) have been experimentally determined using differential scanning calorimetry. Enthalpies and entropies of fusion for the four phenylazophenol derivatives were also measured. Results of these measurements indicate that the three binary systems exhibit only slight deviations from ideality at temperatures between the melting points of the pure components. Deviations become more pronounced in the PAP+EOPAP system as the temperature decreases below the melting pont of the ethoxy-derivative.

A Molecular Statistical Theory of Smectic A Liquid Crystalline Mixtures: Thermal Stability of Smectic A Phase in Binary Mixtures

A molecular statistical theory of smectic A liquid crystalline mixtures is presented. Both the intermolecular repulsions and the attractions are consistently introduced in similar to the previous work on smectic A liquid crystals. 1) The repulsive interaction is approximated in terms of the hard-core potential and is taken into account within the second-virial approximation. The temperature dependence of the order parameters over the smectic-nematic (or isotropic) and nematic-isotropic phase transitions is numerically calculated for several binary mixtures. In addition the phase diagrams of them are constructed. The smectic-nematic (or isotropic) transition temperatures in binary mixtures tend to be increased in comparison with the predicted values in terms of the linear approximation, being consistent with some experimental findings. It is also found that the symmetry-breaking component of one-body pseudo-potential contributes to the thermal stability of smectic A phase in smectic A binary mixtures.

A Molecular Field Treatment of Nematic Liquid Crystalline Mixtures: Effects of the Intermolecular Requlsions on Nematic-Isotropic Phase Transition in Binary Mixtures

The internaolecular repulsions are approximately introduced into the molecular field theory of multi-component system of nematogens developed by Humphries-James-Luckhurst 1) (H-J-L), and its effects on nematic-isotropic transition temperatures are investigated in binary mixtures of nematogens. From the comparison of the theoretical and experimental results, one can conclude that the intermolecular repulsions are also important to treat the nematic-isotropic phase transition in binary mixtures in addition to the intermoleculer attractions. It is found that the effects of the intermolecular repulsions tend to lower the nematic-isotropic transition temperatures in binary mixtures.

Effect of molecular structure on mesomorphism. 7. Enhancement of smectic-isotropic transition temperatures in binary mixtures of a new liquid crystal series: the 4-nitrophenyl 4'-n-alkoxybenzoates

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of molecular structure on mesomorphism. 7. Enhancement of smectic-isotropic transition temperatures in binary mixtures of a new liquid crystal series: the 4-nitrophenyl 4'-n-alkoxybenzoatesAnselm C. Griffin, Richard F. Fisher, and Stephen J. HavensCite this: J. Am. Chem. Soc. 1978, 100, 20, 6329–6333Publication Date (Print):September 1, 1978Publication History Published online1 May 2002Published inissue 1 September 1978https://doi.org/10.1021/ja00488a006RIGHTS & PERMISSIONSArticle Views103Altmetric-Citations42LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (659 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts