Thermodynamics of Extremely Diluted Aqueous Solutions

An extensive thermodynamic study has been carried out on aqueous solutions ob- tained through successive dilutions and succussions of 1% wt/vol of some solutes up to extremely diluted solutions, (less than l × 10−5 mol kg−1 ) obtained via several 1/ 100 successive dilution processes. The interaction of acids or bases with the ex- tremely diluted solutions has been studied calorimetrically at 25°C. Measurements have been performed of the heat produced by the mixing of acid or basic solutions of different concentrations, with bidistilled water or with the extremely diluted so- lutions. Despite the extreme dilution of the solutions, an exothermic heat of mixing in excess has been found in about the 92% of the cases, compared to the correspond- ing heat of mixing with the untreated solvent. Here, we show that successive dilu- tions and succussions may permanently alter the physical-chemical properties of the solvent water. The nature of the phenomenon here described still remains unex- plained, but significant experimental results are obtained. A thermodynamic study on aqueous solutions gives interesting information about the behavior of solutes and their interactions with the solvent. The interaction of ac- ids or bases with the extremely diluted solutions has been studied calorimetrically at 25°C. The extremely diluted solution is obtained starting from a solution at 1% wt/ vol. After succussion, that solution is named 1CH preceded by the name or formula of the solute. The succussion process consists of vertical shakings of the solution by means of a mechanical apparatus. In a simple succussion process, 100 vertical strokes in six seconds are given to the glass vessel containing the solution. To pre- pare the successive dilution, 1 g of this solution is added to 99 g of water that again gets succussed, obtaining the 2CH solution. The iteration of this process produces the extremely diluted solutions studied. Measurements have been performed of the heats of mixing of acid or basic solutions of different concentrations with bidistilled water or with solutions, at a concentration of 0.01 mol kg−1, used as reagent, whereas the concentrations of the extremely diluted solutions or with extremely diluted solu- tions. Procedures for the calorimetric determination of the heat of dilution or mixing are well developed.1 The experimental results are treated according to the MacMill- an-Mayer approach,2 modified by Friedman and Krishnan.3 The enthalpies of mix- ing two solutions are given by the following equations: ∆Hmix(J kg−1) = hxxmx f(mx f − mx i) + 2hxymx fmy f + hyymy f(my f − my i) + higher terms