Properties Of Liquid Mixtures Research Articles

In English

The temperature and interfacial behaviors of individual and mixed liquids are of importance from a practical point of view because changes in the phase state of compounds with decreasing temperature could lead to negative effects (e.g., frost damage of porous materials). However, the use of certain mixtures may prevent these negative effects due to the colligative properties of the solutions (cryscopic effects, CE) that lead to several effects including relative lowering of vapor pressure, boiling point elevation, and freezing point depression (FPD). Confined space effects (CSE) also leading to the freezing point depression can affect the colligative properties of liquid mixtures with respect to FPD. One could assume that for some systems with certain FPD due to CE for bulk solutions, there is no additivity (synergetic effect) of CSE and CE, but for others, the opposite results could be. To elucidate these interfacial phenomena, a set of liquid mixtures bound to different adsorbents could be studied using low-temperature NMR spectroscopy. The solutions included acids, bases, and salts as solutes, some liquids (e.g., dimethylsulfoxide, acetonitrile, n-decane) as co-sorbates and others (e.g., CDCl3, CCl4) as dispersion media. The adsorbents included various porous and highly disperse silicas, fumed alumina, carbons (activated carbons, graphene oxides), and porous polymers. So wide ranges of the systems studied could allow one a deeper insight into competitive or additive CSE and CE influencing the interfacial and temperature behaviors of bound liquids. The results of this analysis are of interest from both practical and theoretical points of view.

Interfacial Phenomena in Nanostructured Systems with Various Materials.

Interfacial phenomena linked to the behavior of bound water, organic solvents (co-sorbates, dispersion media), hydrogen, methane, acids/bases, and salts bound to various silicas, polymers, and carbon materials were analyzed vs. temperature and concentrations using 1 H NMR spectroscopy, differential scanning calorimetry (DSC) and other methods. The material characteristics were studied using microscopy, infrared spectroscopy (IR), small angle X-ray scattering (SAXS), and nitrogen adsorption. Confined space effects (CSE) result in enhanced freezing point depression (FPD) and stronger diminution of solvent activity and colligative properties of liquid mixtures in narrower pores. Short hydrophobic functionalities (≡Si-CH3 , =Si(CH3 )2 ) at a silica surface and the presence of nanopores result in differentiation of bound water into weakly (WAW, δH =0.2-2.0 ppm) and strongly (SAW, δH =4-6 ppm) associated waters of smaller solvent activity in smaller clusters located in narrower pores and unfrozen below a bulk freezing point. These effects are enhanced in hydrophobic dispersion media. Hydrophobic liquids could displace bound water into narrower pores inaccessible for their molecules larger than water and/or into broader pores to reduce contact area between immiscible liquids. The observed phenomena depend on sorbent/sorbate kinds and play an important role on practical applications of various sorbents.

Experimental analysis of volumetric, acoustic, viscometric and optical properties of water with 1-amino-2-propanol, 1,2-diaminopropane and 1,3-diaminopropane at T=298.15 -318.15 K: Molecular Modelling by Graph, PFP and IR spectroscopy investigations

BackgroundLiquid mixtures are used as a solvent in most of the natural systems and chemical processes. Therefore, the physicochemical properties of liquid mixtures at different compositions and at different temperatures have a significant role in the optimization of chemical processes. The present report involves the analysis of the thermophysical properties of water (1) and amines (2). MethodsDensity, ρ, dynamic viscosity, η, refractive index, nD, and speed of sound, u, data were measured for binary mixtures of water (1) and amines (1A2P (1-amino-2-propanol), 1,2-DAP (1,2-diaminopropane) and 1,3-DAP (1,3-diaminopropane) (2) at five different temperatures (T = 298.15 to 318.15 K) and at 0.1 MPa pressure. Based on experimental data, the excess molar volume, VmE, deviation in dynamic viscosity, Δη, excess Gibbs free energy of activation, G*E, deviation in refractive index, ΔnD, excess ultrasonic speed, uE, excess isentropic compressibility, KsE, deviation in free volume, ΔVf, excess available volume, VaE, and excess intermolecular free length, LfE, were calculated and these evaluated properties were fitted to Redlich-Kister polynomial (R.K.). The VmE data was analyzed by Prigogine-Flory-Patterson (PFP) theory. The dynamic viscosity, η, values were studied by different correlations. The VmE and Δη data were also analyzed by Graph theoretical approach (GTA). Raman and FT-IR spectroscopic studies give important information about the intermolecular interactions present between unlike molecules water (1) and amines (2) which is also recognized by GTA. Significant findingsThe value of VmE and KsE values were found negative over the whole composition range, and it follow the sequence as: 1,2-DAP > 1,3-DAP > 1A2P with water at equimolar composition. GTA and PFP well supported the VmE data. GTA studies help in investigating the specific intermolecular interactions between unlike components. Further, Graph theory studies predicted OH—–NH interaction is dominant interaction among all interactions which were also supported by Raman and FTIR spectroscopic studies.

Multi-optimization of operational parameters for malt extract production by centrifugal block freeze concentration

This study aims to optimize light and dark malt extract production by centrifugal block freeze concentration (CBFC), considering simultaneous optimization of solids concentration (SC), concentration efficiency (CE), and concentrate percentage (CP) using a desirability function approach. Two cycles and one recycle of CBFC were evaluated for both malt extracts. A central composite rotational design was employed to predict the effects of freezing temperature (FT) and centrifugal time (t) on malt extract production. The desirability function approach was used for optimization. In scenarios with the highest optimization, operational parameters varied from −29.63 °C to −25.90 °C for FT and 7.00 min to 10.16 min for t. Optimized response values ranged from 2.99°Brix to 26.13°Brix for SC, 69.14% to 86.23% for CE, and 38.30% to 43.86% for CP. The results suggest that optimizing CBFC cycles hinges on liquid mixture properties, and diverse input parameters may be necessary for attaining optimal outcomes.

Viscosities of 1,2-DAP + alkyl acetates binary liquid mixtures at T = 298.15–318.15 K: Theoretical interpretation by Graph theoretical approach (GTA) and Bloomfield and Dewan (BFD) model

The liquid mixtures are used as a solvent in most of the natural systems and chemical processes. Therefore, the physicochemical properties of liquid mixtures at different compositions and at different temperatures have a significant role in the optimization of chemical processes. In the present report, the dynamic viscosity (η) of 1,2-DAP (1,2-Diaminopropane) (1) with AAc (alkyl acetates) (C1-C4) (2) were measured at different temperatures (T = 298.15 to 318.15 K) at pressure 0.1 MPa. Deviation in dynamic viscosity, Δη, and excess Gibbs free energy of activation, G∗E, for these binary mixtures were calculated from measured dynamic viscosity data and fitted to Redlich-Kister polynomial equation (R.K.). Δη data were examined in terms of the Bloomfield and Dewan (BFD) model and Graph theoretical approach (GTA) to study the intermolecular interactions in binary mixtures. Further, different correlation like Hind-McLaughlin-Ubbelohde, Bingham, Arrhenius, Kendall, Heric-Brewer, Kendall-Monroe, Tamura-Kurata, Lulian, Grunberg-Nissan, Krishnan-Laddha Frenkel, Katti-Chaudhari, Heric and McAllister were used to correlate η values.

Effects of intramolecular chain conformation on the hydration and miscibility of polyethylene glycol in water studied by means of polymer reference interaction site model theory.

To examine the conventional idea that the gauche conformation of the OCCO dihedral angle promotes the dissolution of polyethylene glycol (PEG) in water through strong hydration, the thermodynamic properties of liquid mixtures of PEG and water were studied by means of polymer reference interaction site model (PRISM) theory. The intramolecular correlation functions required as input for PRISM theory were calculated by the generator matrix method, accompanied by changes in the distribution of dihedral angles. In the infinite dilution limit, the increased probability of gauche conformation of the OCCO dihedral angles stabilizes the hydration of PEG through enhanced hydrogen bonding between the ether oxygen of PEG and water. The mixing Gibbs energies of the liquid mixtures were also calculated in the whole concentration range based on the Gibbs-Duhem equation, as per our recent proposal. A liquid-liquid phase separation was observed when all the dihedral angles of PEG were in the trans conformation; for the liquid mixture to be miscible in the whole concentration range, the introduction of the OCCO gauche conformation was found to be indispensable. The above theoretical results support the conventional idea that the OCCO gauche conformation is important for the high miscibility of PEG and water.

Critical review on graph theory: Estimation of thermodynamic properties of liquid mixtures

Critical review on graph theory: Estimation of thermodynamic properties of liquid mixtures

Thermophysical modelling of transport and optical properties of 1-propanol+1,3-diaminopropane or 1,2-diaminopropane or 1-amino-2-propanol binary liquid mixture at T=298.15-318.15 K: Molecular interaction analysis by density functional theory (DFT) and graph theoretical approach (GTA)

BackgroundPure liquid properties cannot always satisfy the need of chemical processes. Therefore, liquid mixtures are preferred in different compositions, and the thermo-physical properties of liquid mixtures are highly significant for different processes. The present report involves thermo-physical of amines and 1-propanol. Amines are utilized for CO2 absorption processes. MethodsThe viscosity (η) and refractive index (nD) of 1P (1-propanol) (1) + Amines (1,3-DAP(1,3-diaminopropane), 1,2-DAP(1,2-diaminopropane) and 1A2P(1-amino-2-propanol)) (2) binary mixture were measured at T = 298.15-318.15 K under the atmospheric pressure 0.1 MPa. Experimental data of η and nD were further used to determine deviation in viscosity (Δη), excess Gibbs free energy of activation (G*E) and deviation in refractive index (ΔnD). Δη were analyzed by Bloomfield and Dewan model (BFD) and also examined in term of Graph theoretical approach (GTA). The η and nD data were further correlated by various relevant correlations Significant findingsThe derived thermo-physical properties were well correlated with Redlich-Kister polynomial equation. DFT studies indicated the strength of molecular interactions and supported the graph theory in predicting probable associative molecular species in the liquid mixtures. Further, in 1P + amines binary liquid mixtures, the dominant interaction is OH—–NH.

General Adsorption Model to Describe Sigmoidal Surface Tension Isotherms of Binary Liquid Mixtures

Surface tension (σ) isotherms of liquid mixtures can be divided into Langmuir-type (L-type, including LI- and LII-type) and sigmoid-type (S-type, including SI- and SII-type). Many models have been developed to describe the σ-isotherms. However, the existing models can well describe the L-type isotherms, but not the S-type ones. In the current work, a thermodynamic model, called the general adsorption model, was developed based on the assumption of surface aggregation occurring in the surface layers, to relate the surface composition with the bulk one. By coupling the general adsorption model with the modified Eberhart model, a two-parameter equation was developed to relate the σ with the bulk composition. Its rationality was examined using the σ data of 10 binary mixtures. The results indicate that the new model can accurately describe the S- and L-type isotherms of binary liquid mixtures, showing a good universality. One advantage of the model is that its two parameters, i.e., the adsorption equilibrium constant (K) and the average aggregation number (n), can be estimated by linear fitting experimental σ data, thereby obtaining unique values. This model suggests that the S- and LII-type isotherms arise from the surface aggregation (n ≠ 1). In addition, the standard molar Gibbs free energy of surface adsorption (ΔG̃ad0) and the apparent surface layer thickness (τ) were analyzed for 10 binary mixtures. The ΔG̃ad0 data suggest that the order of adsorption tendency is LI-type ≫ SI-type ≈ SII-type > LII-type, and the strong adsorption usually corresponds to large τ. This work provides a feasible model for describing the S-type isotherms and a better understanding of the surface properties of liquid mixtures.

Study of phase equilibria and thermodynamic properties of liquid mixtures using the integral equation theory: Application to water and alcohol mixtures.

A theoretical method for calculating the thermodynamic properties and phase equilibria of liquid-liquid mixtures using the integral equation theory is proposed. The solvation chemical potentials of the two components are evaluated by the integral equation theory and the isothermal-isobaric variation of the total density with composition is determined to satisfy the Gibbs-Duhem relation. Given the density of a pure component, the method can calculate the densities of the mixture at any composition. Furthermore, it can treat the phase equilibrium without thermodynamic inconsistency with respect to the Gibbs-Duhem relation. This method was combined with the reference interaction-site model integral equation theory and applied to mixtures of water + 1-alcohol by changing the alcohol from methanol to 1-butanol. The destabilization of the mixing Gibbs energy by increasing the hydrophobicity of the alcohol and demixing of the water-butanol mixture were reproduced. However, quantitative agreement with experiments is not satisfactory, and further improvements of the integral equation theory and the molecular models are required.

Thermodynamic Properties of Binary Liquid Mixtures Containing Furfural with Chlorobenzene, Nitromethane, Diethylmalonate and 1-Butanol at 308.15K and 318.15K Supported by FTIR Spectral Studies

A study on thermodynamic properties of the liquid mixture is used in the industrial process, which often extends to solution chemistry. Density(ρ), Viscosity(η), and Ultrasonic velocity(U) were determined for binary liquid mixtures of furfural with chlorobenzene, nitromethane, diethyl malonate and 1- butanol at temperature of 308.15K and 318.15K at atmospheric pressure over the whole range of mole fractions. The calculated thermodynamic properties and some excess parameters such as Excess Volume(VE), Deviation in Isentropic Compressibility(∆KS), Deviation in Viscosity(∆η), Deviation in Intermolecular Free Length(∆LF), Deviation in Intermolecular Free Volume(∆VF), Deviation in Internal Pressure(∆π) and Deviation in Acoustic Impedance(∆Z) were calculated and applied to the Redlich-Kister type polynomial equation to determine the appropriate coefficients. The effects of composition and temperature on thermodynamic parameters have been studied in terms of molecule interaction in these liquid mixtures. Further, IR spectra of these liquid mixtures were recorded and the data were utilized to examine the mixing behavior of the components.

Study of solvation and pollution approch of atrazine and chlorothalonil pesticides in binary liquid mixtures

Thermodynamic properties of liquid mixtures are communally used to examine the deviation from ideality. The thermodynamic properties, which depend on temperature, composition and pressure, describe interaction between the component molecules. The solubility is a property of solute and solvent that effect on extent of adsorption–desorption of pesticides. Hence solution chemistry utilized for investigation of environmental fate of agrochemicals and pollutants in the environment. Some pesticides can leach through the soil and enter into the groundwater. In India about 60 % of the population depends upon ground water for drinking purpose and almost 95 % of the households in rural areas use ground water as their primary source of drinking water. Drinking water supplies might be contaminated by pesticides. The excess use of pesticides leads to environmental contamination and the pesticide residues are found in food, water and air. This paper addresses a study of solvation behavior of Atrazine and Chlorothalonil pesticides in binary mixture of DMF and DMSO. The measured densities (ρ) and viscosities (η) at 298.15 to 313.15 K using a bicapillary pycnometer and Ubbelohde viscometer were utilize to study salvation and pollution approach of pesticides. The obtained parameters were interpreted in terms of solute–solute and solute–solvent interactions. The proposed method for study of solvation behavior of pesticides by viscometer is simple, robust and requires less computational time. Each pesticide and solvent molecules are nanoparticles. Recommendation from this research work could help to change physiochemical behavior of pesticides used in agriculture field to becomes more eco-friendly for the sustainable development in environment.

RISE Test Facilities for the Measurement of Ultra-Low Flow Rates and Volumes with a Focus on Medical Applications

In the framework of the ongoing EMPIR JRP 18HLT08 Metrology for Drug Delivery (MeDDII), a main task is to improve dosing accuracy and enable traceable measurements of volume, flow and pressure of existing drug delivery devices and in-line sensors operating, in some cases, at ultra-low flow rates. This can be achieved by developing new calibration methods and by expanding existing metrological infrastructure. The MeDDII project includes, among other issues, investigations on fast changing flow rates, physical properties of liquid mixtures and occlusion phenomena to avoid inaccurate measurement results and thus improve patient safety. This paper describes the extension of an existing measurement facility at RISE and the design and construction of a new measurement facility to be able to carry out such investigations. The new measurement facility, which is based on the dynamic gravimetric method, is unique worldwide in respect of the lowest measurable flow rate. The gravimetric measuring principle is pushed to the limits of what is feasible. Here, the smallest changes in the ambient conditions have a large influence on the measurement accuracy. The new infrastructure can be used to develop and validate novel calibration procedures for existing drug delivery devices over a wide flow rate range. The extension of the measurement facilities also enables inline measurement of the pressure and the dynamic viscosity of Newtonian liquids. For this purpose, it is ensured that all measurements are traceable to primary standards.

First-Order Prediction of the Relative Performance of Infrared (IR) Absorption, Raman, and Combined (IR + Raman) Spectroscopy for Estimating Composition and Bulk Properties of Fuel Mixtures

Using published infrared (IR) absorption and Raman scattering data for pure species, we performed simulations to gain insight into the performance of IR and Raman spectroscopy when applied to estimate the composition and properties of liquid mixtures. We also considered IR absorption applied to the evaporated mixtures. Using hypothetical mixtures composed of 237 pure species, we investigated estimation of molecular weight (MW) and density. Using hypothetical mixtures composed of 41 species, we investigated estimation of derived cetane number (DCN) and enthalpy of combustion (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) in addition to MW and density. For the 237-species problem, we found that Raman outperformed gas-phase IR by a factor of up to 1.6, and combined (Raman + gas-phase IR) spectroscopy outperformed Raman alone by a factor of up to 3.4. Similar trends were seen in the 41-species problem: for example, Raman was 1.2 times better for estimating DCN than gas-phase IR, and combined spectroscopy was 1.5 times better than Raman alone. We also estimated the performance for absorption in limited IR ranges: 600–1700 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> (fingerprint region), 2650–3200 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text {-1}}$ </tex-math></inline-formula> (CH stretch region), and 3400–4500 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text {-1}}$ </tex-math></inline-formula> . The fingerprint region performed only 1.2–1.6 times worse than the full range (600–6500 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text {-1}}$ </tex-math></inline-formula> ), but the other ranges resulted in higher errors. For example, the CH stretch region performed 5–8 times worse. Gas-phase IR outperformed liquid-phase IR by a factor of up to 1.6 when using the full range.

Comparative Study of Physicochemical and Acoustic Properties of Binary Liquid Mixtures of Cyclopentyl Methyl Ether with Chlorobenzene and Cyclopentyl Methyl Ether with Methyl Acrylate at 298.15 K Temperature

Physicochemical and acoustic propertie of liquid mixtures give knowlegeble information behaviour and interactions studies of liquids. Ultrasonic studies in liquids and solutions provide some valuable information about the structure and interaction in such systems. Ultrasonic velocity and density have been proved to be important properties to test the validity of liquid state model. The ultrasonic velocity (U) and density (ρ) of the binary liquid mixtures Chlorobenzene (polar)+Cyclopentyl methyl ether (nonpolar) [system I] and Methyl acrylate (polar) +Cyclopentyl methyl ether (nonpolar) [system II] are measured at 298.15 K temp. with pure components. With the help of these measured properties are calculated excess acoustic parameters using standard relations. Excess acoustic parameters are used as a qualitative and quantitative analysis in multicomponent liquid mixtures. The sign and magnitude of excess parameters provided information of different type interactions. Structural chemistry is related to the interactions involved in the liquid systems. structural effects also define nature and bonding of both liquid mixture system I and II.

Mechanisms ruling the lifetimes of films of liquid mixtures

Foams and bubbles formed in liquid mixtures have lifetimes longer by several orders of magnitude than in pure liquids of similar viscosities. We have shown recently that this effect results from slight differences in molecular concentrations between bulk and surfaces, which give rise to a thickness-dependent surface tension of liquid films. We present a quantitative description of the enhanced stability of liquid films in binary mixtures, based on experimental data and theoretical analysis. Experiments were performed with mixtures of different natures and compositions: foams of stationary heights were obtained by continuous injection of gas, on one hand, and single bubbles were swollen under the surface of a liquid bath, on the other hand. Remarkably, the lifetimes measured in both experiments exhibit the same variations with mixture composition, and follow a power law with the microscopic length that characterises the amplitude of the thickness-dependent surface tension. In addition, the lifetimes vary with the squared film thicknesses at the onset of bursting. We suggest that two stages occur between the birth of liquid films and their rupture. We show how the thickness-dependent surface tension allows an equilibrium shape to be reached at the end of a first stretching stage. We give an analytical description of this shape, which is fully consistent with experimental findings. We suggest a possible mechanism for final rupture of the film, and discuss it in light of existing theoretical predictions. Finally, we compare the properties of liquid mixtures and surfactant solutions, and in particular their surface rheology.

Study of thermo-acoustical properties of Liquid mixtures of Aqueous solution of Lithium Chloride and Lithium Hydroxide at Different Temperatures

Density, viscosity and ultrasonic velocity of the various compositions of liquid mixtures of aqueous solutions of Lithium chloride (LiCl) and Lithium hydroxide (LiOH) have been experimentally measured at 303,308,313 and 318K and at atmospheric pressure. From these experimental measurements the acoustic impedance (Z) and adiabatic compressibility (ad) have been calculated. The variations in these parameters have been correlated to derive the intermolecular interactions taking place between the mixtures of present study.

Numerical study of the evaporation and thermal decomposition of a single iron(III) nitrate nonahydrate/ethanol droplet

The heating, evaporation, and possible thermal decomposition of spherically symmetric droplets consisting of a precursor solution of iron(III) nitrate nonahydrate (INN) and ethanol (EtOH) for nanoparticle synthesis in spray flames are studied numerically. The multicomponent droplets are at standard conditions and the evaporation is initiated through the elevated temperature of the convective ambience. The liquid mixture properties of INN and ethanol used in the model are fits to new experimental data. In general, there are two different pathways through which the nanoparticle synthesis may occur from the precursor solution. In one pathway, the particle forms directly inside the liquid precursor solution, and in another pathway, the droplet is transferred entirely into the gas phase from which the nanoparticle may form. The process is initially governed by the evaporation of ethanol and of the water from the INN. For ambient gas temperatures below the thermal decomposition temperature Tth of INN, the evaporation eventually leaves behind an iron(III) nitrate particle and for higher temperatures beyond Tth, thermal decomposition and liquid-phase reactions may occur inside the precursor droplet, transferring the iron(III) nitrate entirely into gaseous Fe2O3 and N2O5, so that the entire liquid droplet transforms into the gas phase. Parameter studies of the evaporation of the INN/ethanol droplet for both situations are presented. Moreover, the process in both dry and humid air is investigated. The water condensation on the droplet surface prolongs the droplet evaporation time and leads to higher droplet surface temperatures for high ambient gas temperatures, promoting thermal decomposition of the iron(III) nitrate.

Thermodynamic properties of liquid mixtures containing cyclic amines and isomeric picolines: excess molar volumes and excess isentropic compressibilities and excess heat capacities

The present study reports densities, ρ, speeds of sound, u, molar heat capacities, CP of binary piperidine or 1-methylpiperidine (1) + 2- or 3- or 4-picolines (2) mixtures over entire composition range by varying temperature range from 293.15 to 308.15 K with step of 5 K interval. Experimental data have been used to access excess molar volumes, VE, excess isentropic compressibilities, $$\kappa_{{\rm S}}^{\text{E}}$$ and excess heat capacities, $$C_{{\rm P}}^{\text{E}}$$ . The VE, $$\kappa_{{\rm S}}^{\text{E}}$$ and $$C_{{\rm P}}^{\text{E}}$$ data have been fitted to Redlich–Kister polynomial equation to evaluate the adjustable parameters and standard deviations. The $$C_{{\rm P}}^{\text{E}}$$ data of piperidine (1) + 2- or 3- or 4-picolines (2); 1-methylpiperidine (1) + 3- or 4-picolines (2) are positive and those for 1-methylpiperidine (1) + 2-picoline (2) mixture, sign and magnitude of $$C_{{\rm P}}^{\text{E}}$$ values change with increase in mole fraction of 1-methylpiperidine. Further, VE and $$\kappa_{{\rm S}}^{\text{E}}$$ of 1-methylpiperidine (1) + 2- or 3- or 4-picolines (2); piperidine (1) + 2- or 3-picolines (2) are negative; and those for piperidine (1) + 4-picoline (2) are positive across full range of composition. The VE, $$\kappa_{{\rm S}}^{\text{E}}$$ and $$C_{{\rm P}}^{\text{E}}$$ data have been utilized to test the applicability of Graph theory. It has been observed that VE, $$\kappa_{{\rm S}}^{\text{E}}$$ and $$C_{{\rm P}}^{\text{E}}$$ values calculated from the Graph theory compare reasonably well with their corresponding experimental values. The Quantum mechanical calculations and IR spectral studies on the aforesaid mixtures support the presence of various molecular entities (estimated by analyses of VE data) in pure and mixed state.

Polarizability relaxation in water/ethanol mixtures

Molecular dynamics simulations are used to investigate structural and dynamical properties of liquid mixtures of water and ethanol over the entire range of compositions from neat liquid water to neat liquid ethanol. Particular emphasis is given to the time relaxation of the anisotropic collective polarizability and the low-frequency part of the depolarized Raman spectra. While the dynamics was carried out using simulations with standard force fields for water and ethanol, the post-analysis was performed employing the chemical potential equalization (CPE) method. For comparison purposes, the CPE results are compared to those obtained with the traditional interaction-induced model. Both methods are able to capture the basic shape and position of the Raman bands. Polarizability response in time and frequency domains is disentangled in permanent, interaction-induced and induced-permanent (cross) terms. Our findings suggest that the polarizability relaxation of water is more sensitive to environmental fluctuations. Once water signal remains covered by the ethanol contribution even in water-rich concentrations, some water polarizability features were unveiled and correlated with H-bond dynamics. The permanent term, representative of the reorientational dynamics, captures the short-time oscillations and responds for a part of the total relaxation, while the long-range interaction-induced contribution is responsible for great part of the total polarizability relaxation.