Mario Della Monica

Ionic conductances in water-sulfolane mixtures at 30°C

AbstractConductances of solutions of triisoamyl-n-butylammonium (iAm3BuN+) iodide and sodium tetraphenylboride, iodide, and bromide have been measured in water-sulfolane mixtures at 30°C. Experimental data were analyzed by the 1965 Fuoss-Onsager-Skinner equations. The limiting equivalent conductances of triisoamyl-n-butylammonium tetraphenylboride (iAm3BuNBPh4) in each solvent mixture were obtained by the equation

Transference numbers in concentrated sodium chloride solutions

\Lambda _0 (iAm_3 BuNBPh_4 ) = \Lambda _0 ({\text{i}}Am_3 BuNI) + \Lambda _0 (NaBPh_4 ) - \Lambda _0 (NaI)

Electrochemical investigation of the interaction of different mediators with the photosynthetic reaction center from Rhobobacter sphaeroides

Limiting ionic equivalent conductances in water-sulfolane mixtures were calculated on the assumption thatι0(iAm3BuNBPh4)/2λ0(iAm3BuN+)=λ0(BPh-4). The variations of the limiting ionic Walden product with solvent composition are discussed with respect to current information concerning solvent structural effects and ion-solvent interaction.

23Na NMR relaxation study of sodium dodecyl sulphate in some aqueous and nonaqueous systems

NaCl, NaBr, NaI, NaClO4, KCl, KClO4, NaBPh4, and Ph4PBr solution enthalpies were measured in water-sulfolane mixtures at 30°C. Ionic enthalpies of transfer from water to mixed solvents were calculated on the basis of the assumption ΔΔHso(BPh4−)=ΔΔHso(Ph4P+). The variation of the ionic enthalpies of transfer with solvent composition is discussed in terms of ion-solvent interactions and of the effects caused by sulfolane on the structure of water.

Water photoelectrolysis through the use of electrodes covered by photosystems I and II

The transference numbers of sodium and chloride ions in concentrated NaCl-water solutions have been measured at 25°C, using the Hittorf method. An improvement to determine the concentration has been obtained by weighing the anhydrous salt content of the different portions. The ionic conductivities calculated by data of transference numbers and conductivities of the salt have been compared to the analogous quantities of NaClO4-water system. The analysis of the data seems to prove the existence of a different concentration region where the structural transition of the solutions greatly influences the ionic mobility.

Electrolyte viscosities in hexamethylphosphotriamide at 25°C

Abstract In the present communication, conductivity data of NaSCN-water system up to 9M concentration have been treated with a new equation which introduces in the electrophoretic term of the Wishaw-Stokes equation correction for change of viscosity. The addition of the correction term does not limit the applicability of proposed equation in the range of the very dilute solutions.

Physico-chemical properties of concentrated solutions of some tetraalkylammonium salts in formamide in the temperature range 25–80°

In this paper the electrochemical techniques (chronoamperometry, cyclic voltammetry and linear sweep voltammetry) have been employed in order to study the interactions between different mediators and the reaction center of the photosynthetic bacterium Rhodobacter sphaeroides. The experimental data are interpreted in view of the competitive occurring of an electrochemical reaction of the mediators at the electrode and their chemical reaction with the cofactors of the reaction center. The overall process is modelled by a set of differential equations, integrated using the Runge–Kutta method, that allow the calculation of kch and kel, the kinetic constant of the chemical and electrochemical reactions, respectively. The redox species used as mediators are the ferricyanide and 2,3,5,6-tetramethyl-p-phenylenediamine (DAD), both reductants of the photooxidized dimer, the Ubiquinone-0, which is able to reduce the quinones in the site A (QA) and B (QB) of the protein and the TMPD, an oxidant of the semiquinone anion.

Interactions of photosynthetic reaction center with 2,3-dimethoxy-5-methyl-1,4-benzoquinone in reverse micelles

Abstract The analysis of the 23Na NMR spin-lattice (R1) and spin-spin (R2) relaxation rates was performed on several two-, three-, and four-component systems of the surfactant sodium dodecyl sulphate in water, formamide, N-methyl formamide and N,N-dimethyl formamide. n-pentanol or n-octanol was used as cosurfactant, while p-xylene was added as oil to obtain some aqueous and nonaqueous microemulsions. In several systems R1 = R2, thus indicating that Na+ ions are not tightly bound to any structured interface. Whenever R1 ≠ R2 the use of a two-site model gives a reliable estimate of the dynamic parameters characterizing the motion of the Na+ ions in the bound state. It is worth noting that while, in the aqueous systems, the Na+ ions retain an octahedral coordination (Oh symmetry), a tetrahedral coordination (Td symmetry) of the Na+ ions by FM, NMF, and DMF molecules has been proposed as a reasonable explanation of the observed high-field shifts and increase in the quadrupolar coupling constant.