New Physico-Chemical Properties of Extremely Diluted Aqueous Solutions

The extremely diluted solutions are anomalous 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^-5mol kg^-1) to the point that we may call the resulting solution an extremely diluted solution, namely the composition of the solution is identical to that of the solvent used (e.g. twice distilled water). We conducted thermodynamic and transport measurements of the solutions and of the interaction of those solutions with acids or bases. The purpose of this study is to obtain information about the influence of successive dilutions and succussions on the water structure of the solutions under study. We measured the heats of mixing of acid or basic solutions with such extremely diluted solutions, their electrical conductivity and pH, comparing with the analogous heats of mixing, electrical conductivity and pH of the solvent. We found some relevant exothermic excess heats of mixing, higher electrical conductivity and pH than those of the untreated solvent. The measurements show a good correlation between independent physico-chemical parameters. Care was taken to take into account the effect of chemical impurities deriving from the glass containers. Here we thus show that successive dilutions and succussions can permanently alter the physico-chemical properties of the water solvent. The nature of the phenomena here described still remains unexplained, nevertheless some significant experimental results were obtained. This revised version was published online in August 2006 with corrections to the Cover Date.     

Interactions between aminoacids and alcohols in water at 25 °C

The enthalpies of dilution of ternary aqueous solutions containing an alcohol (ethanol,n-propanol,n-butanol or tert-butanol) and an aminoacid or a peptide (glycine, glycyl-glycine or glycyl-glycyl-glycine), were measured at 25 °C. The results were used to calculate pair cross interaction parameters between solutes. The coefficients of virial expansion of the excess enthalpies are compared with those referring to solutions containing the same alcohols and other structure-breaking solutes (urea, thiourea and biuret). The enthalpic pair parameter for the systems glycine-alcohols shows the same trend, as reported in the literature, for similar structure-breaking solutes, with a maximum in the cross coefficients when reported versus the self pair interaction coefficients of alcohols. The results are interpreted in terms of a prevailing release of water from the cospheres of alcohols.

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Zusammenfassung Die Verdünnungsenthalpien ternärer wässeriger Lösungen, die einen Alkohol (Ethanol,n-Propanol,n-Butanol odertert-Bulanol) und eine Aminosäure oder ein Peptid (Glycin, Glycil-glycin oder Glycyl-glycyl-glycin) enthalten, wurden bei 25 °C gemessen. Die erhaltenen Werte wurden zur Berechnung der Parameter der zwischen den Molekülen der verschiedenartigen gelösten Stoffe auftretenden Wechselwirkungen herangezogen. Die Koeffizienten der Virialentwicklung der Überschussenthalpien werden mit denen verglichen, die sich auf die gleichen Alkohole und andere strukturbrechende gelöste Stoffe (Harnstoff, Thioharnstoff und Biuret) enthaltenden Lösungen beziehen. Die Enthalpieparameter der Systeme Glycin-Alkohole zeigen den in der Literatur für ähnliche strukturbrechende gelöste Stoffe mitgeteilten Trend nämlich ein Maximum in der Kurve, die beim Auftragen der Koeffizienten der Wechselwirkung zwischen verschiedenartigen Molekülen gegen die Koeffizienten der Wechselwirkung zwischen den Alkoholmolekülen erhalten wird. Die Ergebnisse werden unter Annahme eines bevorzugten Austritts von Wasser aus der Kosphäre der Alkohole interpretiert.

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This work is financially supported by the Italian Ministry of Public Education and by the Italian National Research Council.     

Four-membered rings family in the Si–O extended rocking IR band from quantum chemistry calculations

We calculate the vibrational modes of four-membered rings family in the Si–O extended rocking infrared for vitreous SiO₂ materials. In particular these species are obtained in the early stages of the sol–gel process. We have performed high quality quantum-mechanical calculations based on cluster models and gradient corrected density functional theory, (GC-DFT). Three possible configurations were obtained, a regular planar, a slightly deformed or quasi-planar, and a deformed ring. According to our result, the more probable one is the slightly deformed configuration. The calculated vibrational frequencies are compared with experimental IR and Raman results obtaining very good agreement. Also, we calculated geometries and vibrational frecuencies for three-membered rings. We found that 3- and 4-fold rings show evidence of decoupled vibrational modes, those modes are compared with a Raman spectrum obtaining very good coincidence.