Excess Heat Of Mixing Research Articles

Calorimetric and conductometric titrations of nanostructures of water molecules in iteratively filtered water

This work continue the study of the physico-chemical properties of samples of pure, twice distilled water, when subject to a procedure of iterative filtrations through Pyrex glass filters (Buchner funnels). After the filtrations, electrical conductivity and heat of mixing with NaOH and HCl solutions increase. The hypothesis is that the iterative filtration procedure, that involves a flux of energy and material in an open system, is able to induce the formation of “dissipative structures” or nanostructures of water molecules (WNS). Water exhibits an extraordinary auto-organization potentiality triggered by several kinds of perturbations, including mechanical ones. We measured the heats of mixing of acid or basic solutions with such iterated filtered waters (IFW) and their electrical conductivity, comparing with the analogous heats of mixing, electrical conductivity of the solvent. We found some relevant exothermic excess heats of mixing and higher conductivity than those of the untreated solvent. The heats of mixing and electrical conductivity of IFW show a good correlation, underlining a single cause for the behavior of the samples.

A Kirkwood-Buff Derived Force Field for Aqueous Alkali Halides

A classical nonpolarizable force field is presented for the simulation of aqueous alkali halide solutions (MX), where M = Li(+), Na(+), K(+), Rb(+), Cs(+) and X = F(-), Cl(-), Br(-), I(-), and their interactions with biomolecules. The models are specifically designed to reproduce the experimental Kirkwood-Buff integrals, and thereby the solution salt activities, as a function of salt concentration. Additionally, we demonstrate that these models reasonably reproduce other experimental properties including ion diffusion constants, dielectric decrements, and the excess heats of mixing. The parameters are developed by considering the properties of aqueous NaX and MCl solutions using a previously established model for NaCl. Transferability of the parameters to other salts is then established by the successful simulation of additional aqueous salt solutions, KI and CsBr, not originally included in the parameterization procedure.

On the stability of extremely diluted aqueous solutions at high ionic strength

An extensive study has been carried out on extremely diluted aqueous solutions (EDS). These solutions revealed a really intriguing physico-chemical behaviour, characterized by multiple independent variables. Because of their behaviour, EDS can be described as far-from-equilibrium systems, capable of self-organization as a consequence of little perturbations. In this paper we investigate the stability of the calorimetric behaviour of EDS with a high ionic force, due to the presence of the sodium chloride electrolyte. We measured the excess heats of mixing of EDS with basic solutions, both with and without a high concentration of NaCl, and compared the results. In particular, we explored these concentrations: 0.5 and 1Mmol kg−1). The analysis of the experimental results shows that the calorimetric response of the EDS is stable when they are in a concentrated solution of NaCl. That is of great relevance for the eventual pharmacological action of these solutions, since it involves the interaction with fluids of complex chemical composition and high concentration.

New Physico-chemical Properties of Water Induced by Mechanical Treatments. A calorimetric study at 25°C

An extensive thermodynamic study has been carried out on aqueous solutions, obtained through the iteration of two processes: a dilution 1:100 in mass and a succussion. The iteration is repeated until extreme dilutions are reached (less than 1⋅10–5 mol kg–1 ) to the point that we may call the resulting solution an 'extremely diluted solution'. We conducted a calorimetric study, at 25°C, of the interaction of those solutions with acids or bases. Namely, we measured the heats of mixing of acid or basic solutions with bidistilled water and compared them with the analogous heats of mixing obtained using the 'extremely diluted solutions'. Despite the extreme dilution of the latter solutions, we found a relevant exothermic excess heat of mixing, excess with respects to the corresponding heat of mixing with the untreated solvent. Such an excess has been found in about the totality of measurements, and of a magnitude being well beyond one that could arise any issue of sensibility of the instrumental apparatus. Here we thus show that successive dilutions and succussions can permanently alter the physico-chemical properties of the solvent water. The nature of the phenomena here described still remains unexplained, nevertheless some significant experimental results were obtained.

Excess molar enthalpies of eight binary mixtures containing 1,2-epoxybutane + ethyl alkanoates at 298.15 K

Excess molar enthalpies, H E m, have been measured using a flow microcalorimeter at 298.15 K and at atmospheric pressure for the eight mixtures containing 1,2-epoxybutane with ethyl acetate, ethyl propanoate, ethyl butyrate, ethyl pentanoate, ethyl hexanoate, ethyl heptanoate, ethyl octanoate and ethyl decanoate. Excess heats of mixing, H E m, are positive for all the mixtures and increase with the chain length of the alkanoate, with the exception of ethyl acetate whose H E m values were between those of ethyl pentanoate and ethyl hexanoate. Results have been correlated in terms of the Redlich–Kister equation and qualitatively discussed in terms of molecular interactions.

Excess heat of mixing of pyridine bases with toluene

The excess heats of mixing of pyridine bases with toluene at 298.15 K were measured, and the Prigogine-Flory-Patterson theory was applied to describe the experimental results.

Excess heat of mixing of α-picoline withn-alkanes

The excess heats of mixing for binary mixtures α-picoline +n-alkanes (C6 to C10) at 298.15 K were measured and a comparison was made with the Prigogine-Flory-Patterson theory and the extended real associated solution method.

Excess heat of mixing of binary mixtures of pyridine withn-alkanes at 313.15 K

The molar excess enthalpies of binary mixtures of pyridine with C6–C9n-alkanes have been measured at 313.15 K in the entire composition range. The measuredHE values were compared with those calculated by means of the Prigogine-Flory-Patterson theory and by the ERAS method.

A modified temkin's model to describe molten salt binary systems involving complex associations

A description of a new ionic model entitled “entrapped ion model” which is useful for the determination of the stoichiometry of single complex association present in molten salt binary mixtures and for the determination of its stability equilibrium constant is presented. The method described may be applied to any extensive property of the system, additive with respect to the constituants. The method was successful for systems having a common anion, mono-mono or mono-bivalent, the properties considered being excess heat of mixing, excess molar volume and excess molar extinctions (from absorption spectra).

Weak dipolar interaction in solutions

In continuation of our earlier work, excess heats of mixing and volume changes of mixing have been measured for mixtures of chlorobenzene + toluene and chlorobenzene + benzene. The results have been analyzed both in the light of Balescu's theory and our modified approach reported earlier. Analysis shows that our modified approach gives better agreement and the systems should be treated as a mixture of polarizable polar and polarizable non polar molecules.