Microheterogeneity in aqueous-organic solutions: Heat capacities,volumes and expansibilities of some alcohols,aminoalcohol and tertiary amines in water

The heat capacities per unit volume and the densities of aqueous solutions of 2-propanol, neopentanol, tert-amylalcohol, 2-amino-2-methylpropanol, triethylamine and diethylmethylamine were measured, in many cases as a function of temperature, over the whole mole fraction or solubility range. Apparent and partial molal heat capacities, volumes and expansibilities were derived. The concentration dependence of these functions suggest the existence of transitions in some of these systems, in the water-rich region, qualitatively similar to micellization. The large relaxation contribution observed with some of the thermodynamic functions of hydrophobic alcohols and amines suggests a reinforcement of hydrophobic hydration due to strong hydrogen-bonding interactions of the polar groups with water.     

S-Shaped composition dependence of excess thermodynamic quantities for cyclohexane mixtures with globular alkanes

Expansion coefficients , isothermal compressibilities, thermal pressure coefficients and heat capacities have been measured at 25°C for the cyclohexane+trans-decalin system. An S-shaped composition dependence, positivelnegative for highllow cyclohexane compositions is found for C _p ^E dV ^E /dT and the thermal expansion contribution to C _p ^E namely VT. The thermal motion contribution to C _p ^E , namely C _v is close to zero. The positive excursion of these mixing quantities at high cyclohexane content is anomalous. Correspondingly, the mixing quantity-VT deviates strongly in this region from the predicted equality with H ^E . The literature and this work show that all these excess quantities behave similarly for cyclohexane mixed with cyclooctane, methylcyclohexane and some highly branched alkanes. The unusual composition dependence of the thermodynamic quantities is consistent with order occurring when any large alkane molecule of globular shape is added to cyclohexane. This is speculatively associated with an interference by the globular alkane with the relatively free rotation of cyclohexane molecules.     

Molar volumes and ion pairing of lithium halides in alcohols

The concentration dependence of the apparent molar volumes of lithium halides (and electrolytes in general) in alcohols (and solvents permitting association in general) is, in the first instance, due to changes in the degree of association and to the inherent difference between the apparent molar volumes of the ions and of the ion pairs. Previous publications on the molar volumes of electrolytes in organic solvents, disregarding altogether ion pairing, appear to be incorrect. Data from the literature for lithium chloride and lithium bromide in normal primary alcohols and several branched alcohols from C₁ to C₈ and data from our laboratory for lithium halides in 1-hexanol and 2-ethyl-1-hexanol served for the determination of φ _V and φ _E . Electrical and structural contributions to the values of these functions for the ions and for the ion pairs are discussed.     

Apparent Molar Volume, Heat Capacity, and Conductance of Lithium Bis(trifluoromethylsulfone)imide in Glymes and Other Aprotic Solvents

Lithium bis(trifluoromethylsulfone)imide (LiTFSI) is a promising electrolyte for high-energy lithium batteries due to its high solubility in most solvents and electrochemical stability. To characterize this electrolyte in solution, its conductance and apparent molar volume and heat capacity were measured over a wide range of concentration in glymes, tetraethylsulfamide (TESA), acetonitrile, -butyrolactone, and propylene carbonate at 25°C and were compared with those of LiClO₄ in the same solvents. The glymes or n(ethylene glycol) dimethyl ethers (nEGDME), which have the chemical structure CH₃–O–(CH₂–CH₂–O) _n –CH₃ for n = 1 to 4, are particularly interesting since they are electrochemically stable, have a good redox window, and are analogs of the polyethylene oxides used in polymer-electrolyte batteries. TESA is a good plasticizer for polymer-electrolyte batteries. Whenever required, the following properties of the pure solvents were measured: compressibilities, expansibilities, temperature and pressure dependences of the dielectric constant, acceptor number, and donor number. These data were used in particular to calculate the limiting Debye-Hückel parameters for volumes and heat capacities. The infinite dilution properties of LiTFSI are quite similar to those of other lithium salts. At low concentrations, LiTFSI is strongly associated in the glymes and moderately associated in TESA. At intermediate concentrations, the thermodynamic data suggests that a stable solvate of LiTFSI in EGDME exists in the solution state. At high concentrations, the thermodynamic properties of the two lithium salts approach those of the molten salts. These salts have a reasonably high specific conductivity in most of the solvents. This suggests that the conductance of ions at high concentration in solvents of low dielectric constant is due to a charge transfer process rather than to the migration of free ions.     

Seawater—A test of multicomponent electrolyte solution theories. I. The apparent equivalent volume,expansibility, and compressibility of artificial seawater

The apparent equivalent volume _V, expansibility _E, and compressibility _K of an artificial seawater solution containing10 ionic components (Na⁺, Mg²⁺, Ca²⁺, K⁺, Sr²⁺, Cl^–, SO ₄ ^2– , HCO ₃ ^– , Br^–, and F^–) and one nonionic component (H₃BO₃) has been determined from0 to40°C (in5° intervals) and from0.1 to0.8 m ionic strength at1 atm. The concentration dependence (I_v=volume ionic strength) of the _V's, _E's, and _K's have been examined by using a Masson-type equation, = ^° +S'I _V ^1/2, and a Redlich-type equation, = ^° +SI _V ^1/2 +BI _V, where ^° is the infinite-dilution value, S is the empirical Masson slope, S is the theoretical Debye-Hückel slope, and B is an empirical deviation constant. By using Young's rule, = E_i(i), the apparent equivalent volumes, expansibilities, and compressibilities for sea salt have been estimated from the ionic and nonionic components making up the mixture. The estimated apparent molal quantities agree very well with the directly measured values providing the concentration terms, S _i and B_i, are weighted according to the methods of Wood and Reilly.Contribution Number 1599 from the University of Miami.     

Volumetric, Electric, and Magnetic Properties of Thioxanthen-9-one in Aprotic Solvents as Revealed by High-Precision Densitometry, High-Accuracy Refractometry and Magnetic Susceptibility Measurements and by DFT Calculations

High-precision densitometry measurements of solutions of thioxanten-9-one (TX) in 1,4-dioxane, DMSO, toluene, and benzene have been obtained at 293.15, 303.15, 313.15, 323.15, 333.15, and 343.15K. The partial molar volumes of TX ( ) and the corresponding values at infinite dilution ( ) were determined. The partial molar expansibility ( ) of TX at infinite dilution in each solvent is temperature independent. Dynamic electronic polarizabilities of TX in each aprotic solvent were determined by the Singer–Garito approach. These values are in excellent concordance with the theoretical value for TX of 2.611×10⁻²³cm³ estimated here using DFT/B3LYP/6-311++G(d,p). The partial molar volumes of TX at infinite dilution were calculated and interpreted in terms of the Scale Particle Theory (SPT). The solvent influence on the partial molar volume of TX was found to be due mainly to cavity formation and intermolecular dispersion forces.     

Additive and subadditive entropies for discreten-dimensional random vectors

Summary A measure of the amount of uncertainty (entropy) associated with a (discrete) randomn-vector should take into account all kinds of information that is provided. In particular, it should depend both on the range and on the probability distribution of the random vector. In this paper we give acharacterization of those entropies which are expansible, additive, subadditive, partially symmetric and fulfil the said requirement. In the last part of the paper, we discuss the unexpected full symmetry of the mathematical representation of these entropies, as derived. We also suggest possible ways to prevent it.Dedicated to Professor János Aczél on his 60th birthday     

Role of cationic moiety in phosphate fertilizers’ molecules on their solution behavior in terms of volumetric and acoustic parameters at different temperatures and atmospheric pressure

Ultrasonic parameters are very useful tools used to study the physic-chemical behavior and molecular interactions of various liquid mixtures. More than 50% problems of irrigated areas are associated with cultivated land and they frequently occur due to salinity. Application of fertilizers into agricultural land could be a remedy for soil salinity by providing essential nutrients to plants. In this research paper, ultrasonic and volumetric properties of phosphate based fertilizers of different molecular compositions at different temperatures have been studied. This is experimental based work; this knowledge can be employed in formulation of fertilizers according to the nature of their application which could enhance fertilizer’s activity either in terms of nutrients development or to control the salinity of soil. Results obtained from calculated ultrasonic and volumetric parameters indicated presence of strong interactions in aqueous fertilizer solutions which depends upon nature of molecules. Among presently studied phosphate fertilizers i.e. triple superphosphate, nitrophosphate and diammonium phosphate, maximum molecular interactions were observed in aqueous triple super phosphate solutions due to the presence of highly charged cationic specie i.e. calcium ions, which can also be used to control the salinity of soil using electrostatic interactions among saline salts and charged cationic species.     

A Volumetric Study of Water–Decyltrimethylanimonium Bromide–Pentanol Ternary System from 25 to 130°C at 2 and 19 MPa

Density measurements on decyltrimethylammonium bromide (DeTAB)–water and pentanol (PentOH)–DeTAB–water systems as functions of both alcohol and surfactant m _S concentrations were carried out at 2 and 19 MPa from 25 to 130°C. From experimental data for the water–DeTAB binary system, the standard (infinite dilution) partial molar volumes, expansibilities, and compressibilities of DeTAB, and the corresponding properties in the micellar phase are calculated. The trends of the standard partial molar volumes of PentOH V _R ^o in DeTAB micellar solutions as functions of m _S reflect the transfer of PentOH from the aqueous to the micellar phase, except at 130°C and 19 MPa. On the basis of an equation previously used, the distribution constant of PentOH between the aqueous and the micellar phases and the standard partial molar volume of alcohol in the aqueous and the micellar phases are obtained from V _R ^o data. Comparisons with data for PentOH in dodecyltrimethylammonium bromide are made.     

Partial molar volumes in aqueous mixtures of nonelectrolytes. II. Isopropyl alcohol

Densities of isopropyl alconol-water mixtures were measured over the entire mole fraction range at 5, 15, 25, 35 and 45°C. Apparent and partial molar volumes and partial molar expansibilities were derived for both components. The results were compared with those of a previous investigation of t-butyl alcohol-water mixtures.