Thermodynamic parameters for the binding process of the OH 2 ion with the dissipative structures. Calorimetric and conductometric titrations V. Elia • E. Napoli • M. Niccoli Received: 15 December 2009 / Accepted: 22 March 2010 / Published online: 11 April 2010 Ó Akade ´miai Kiado ´, Budapest, Hungary 2010 Abstract Conductometric and calorimetric titrations of Extremely Diluted Solutions (EDS) were performed by adding HCl or NaOH solutions. The aim of this study is to obtain further confirmation of the hypothesized presence, in the EDS, of molecular aggregates of water molecules. The measurements on the EDS evidenced some relevant differences compared to those on solutions with just water as solvent. The conductivity and the pH caused by adding the titrant, namely NaOH or HCl, were markedly different to those of the control solutions. We suppose that the preparation procedure of the EDS could produce non- equilibrium changes in the supramolecular structure of water. The experimental results were interpreted by con- sidering the interactions that can take place between the OH - or H 3 O ? and the hypothesized molecular aggregates of water molecules i.e. dissipative structures. A comparison was made about the nature of the driving force that leads to the formation of the complexes between the two ions deriving from probes and the molecular aggregates of water molecules (dissipative structures). In this study, we have determined the thermodynamic parameters of asso- ciation between molecular aggregates of water molecules (dissipative structures) in the EDS and OH - or H 3 O ? probe ions. The experimental results were interpreted by con- sidering a favorable interaction between the H 3 O ? and OH - ions and the dissipative structures, due, probably, to steric hindrance and chemical affinity with the aggregates. Keywords EDS  Calorimetric titration  Conductometric titration  Complex systems  Dissipative structures Introduction In our recent articles [1, 2], we put forth a new interpretation of conductometric and pHmetric titrations, performed on EDS, using HCl or NaOH as titrants. Based on those con- ductometric and pHmetric measurements, it was hypothe- sized that the particular preparation technique of EDS could lead to an alteration of the structure of the solvent [3–12]. The obtained results enable us to treat the EDS as complex systems that, under the action of perturbations of various natures, are capable of assuming a structural organization characterized by a variation of the local order, through the formation of dissipative structures [13–15] or aqueous nanostructures [16]. The titration curves differ according to the acidic or basic nature of the probe. All the conducto- metric titrations of sodium bicarbonate solutions at different concentrations, using an HCl solution as titrant, show equivalent points in good agreement with the analytic con- centrations. The conductometric titrations of an EDS with HCl exhibit the same shape as that of a titration of a weak base with a strong acid [1]. Within such similitude, we also observe something like an equivalent point for EDS, which we prefer to indicate as a ‘‘break point’’ (b.p). The value of the ‘‘break point’’ is always higher than the equivalent point due to the presence of sodium bicarbonate. The difference between the two values represents the concentration of dissipative structures [1]. The higher the initial conductivity V. Elia (&)  E. Napoli  M. Niccoli Department of Chemistry University ‘‘Federico II’’ of Naples, Complesso Universitario di Monte S’Angelo, Via Cintia, 80126 Naples, Italy e-mail: vittorio.elia@unina.it E. Napoli e-mail: elena.napoli@unina.it M. Niccoli e-mail: marcella.niccoli@unina.it 123 J Therm Anal Calorim (2010) 102:1111–1118 DOI 10.1007/s10973-010-0757-1