Torquato Mussini

Reference value standards and primary standards for pH measurements in D2O and aqueousorganic solvent mixtures: New accessions and assessments (Technical Report)

Recommended Reference Value Standards based on the potassium hydrogenphthalate buffer at various temperatures are reported for pH measurements in various binary solvent mixtures of water with eight organic solvents: methanol, ethanol, 2-propanol, 1,2-ethanediol, 2-methoxyethanol (“methylcellosolve”), acetonitrile, 1,4-dioxane, and dimethylsulphoxide, together with Reference Value Standards based on the potassium deuteriumphthalate buffer for pD measurements in D2O. In addition are reported Primary Standards for pH based on numerous buffers in various binary solvent mixtures of water with methanol, ethanol, and dimethylsulphoxide, together with Primary Standards for pD in D2O based on the citrate, phosphate and carbonate buffers.

Catalytic decomposition of acid hydrogen peroxide solutions on platinum, iridium, palladium and gold surfaces☆

Abstract The catalytic decomposition of acid H2O2 solutions (10−4 to 10−1M) in presence of platinum, iridium, palladium and gold has been studied. In H2SO4 solution, platinum, iridium and palladium are catalytically active; gold is not active. In HCl solution, none of the above metals is active. The H2O2 decomposition is a first order reaction with the following kinetic constants: k = 6·4 × 10−5/sec for platinum; k = 1·2 × 10−5/sec for iridium; k = 0·34 × 10−5/sec for palladium; all at 25°C and referred to a 10 cm2 metal surface. The surface of the electrode becomes practically covered by a monomolecular layer of oxide during the catalytic H2O2 decomposition in acid solution, as shown by anodic and cathodic polarization curves, anodic decay curves and anodic and cathodic charging curves. The metal loses its catalytic activity when it cannot be covered by an adsorbed oxide layer, as when it forms complexes with the solution: for instance, Pt and Ir in HCl solutions or Au in H2SO4 solutions. The different rate of oxide formation by H2O2 and of the reaction between oxide and H2O2 to develop O2 explains the differences of catalytic activity observed between platinum, iridium and palladium. The process of catalytic decomposition of H2O2 acid solutions necessarily involves the intervention of oxides formed on the electrode surface. A kinetic mechanism is proposed to explain the process of H2O2 decomposition, taking into account the independence of the static potential of the H2O2 concentration.

Microcrystalline cellulose powders: structure, surface features and water sorption capability

Characterization of an Avicel PH 102 MCC powder through polymerization degree determination, X‐ray diffraction and N2 adsorptions at subcritical temperatures is described. Specific characterizations of MCC/H2O exchange in different environments were performed by means of thermogravimetric weight losses on time/temperature scale and analyses of water adsorption/absorption from saturated vapors at 310 K. The reversibility of MCC/H2O interactions and the influence of different ‘surface area probes’ on the specific surface area are discussed.

Medium effects as key electrochemical variables for corrosion and electrochemistry studies in non-aqueous and mixed solvents

Abstract Studies in the interdisciplinary area grouping electrochemistry, corrosion and electroanalysis face fundamental problems when comparisons of behaviour of redox systems among different solvents are sought. The pivot variable in this context is the primary medium effect on single ions (or on single electrode potentials) and its definition, determinability, reliability and availability are discussed together with the practical implications on such a popular means as Pourbaixs potential/pH diagram.

Reference value standards for pH measurements in 5, 15 and 30% (w/w) acetonitrile/water solvent mixtures at temperatures from 288.15 to 308.15 K

Abstract Reference value standards, pH (RVS), for 0.05 mol kg −1 potassium hydrogenphthalate (KHPh) reference buffer solutions in 5, 15 and 30% (w/w) acetonitrile/water mixed solvents at temperatures from 288.15 to 308.15 K are determined from reversible e.m.f. measurements of the cell Pt¦H 2 ¦KHPh + KCl¦AgCl|Ag|Pt. Values of the first ionisation constant of o -phthalic acid (H 2 Ph; benzene-1,2-dicarboxylic acid) in these mixed solvents are also determined from analogous measurements. The consistency of the results is analysed by multilinear regression of the quantity p( a HγCl ) as a function of both solution composition and temperature. The standard pH (RVS) values determined are given by the equation pH (RVS) = 4.0080 + 6.330 x + 16.177 x 2 − 115.3 x 3 + 0.3089 u − 201.0 ux 2 + 909 ux 3 + 13.04 v , where x is the mole fraction of acetonitrile in the mixed solvent, u = z /(1 + z ), v = [ln(1 + z ) − u ], z = ( T − θ)/θ, and θ = 298.15 K.

Determination of standard pH values for potassium hydrogen phthalate reference buffer solutions in 10, 20, 50, 64 and 84.2 wt per cent methanol/water mixed solvents at temperatures from 283.15 to 313.15 K

Abstract Standard pH 0 values for 0.05 mol kg −1 potassium phthalate reference buffer solutions in 10, 20, 50, 64 and 84.2 wt % methanol/water solvent mixtures have been obtained from cells without transport, in the temperature range 283.15–313.15 K. The consistency of results has been analysed by a new method of multilinear regression of the quantity p( a H γ Cl ) as a function of both temperature and solution composition. The pH° values found can be reproduced within ± 0.01 by the equation pH 0 = 4.00 + 4.38 x − 5.02 x 2 + 4.23 x 3 + 0.13 z − 0.91 xz , where x = mole fraction of methanol in the solvent mixture, z = ( T − θ)/θ and θ = 298.15 K. Subsidiary values of the first ionization constant of o -phthalic acid in the above solvent mixtures have also been obtained by the buffered cell method.

Electrochemical processes of the bromine/ bromide system☆

Abstract The electrochemical processes of aqueous Br2/Br− system on platinized titanium were studied by the method of the rotating disk electrode. Both the cathodic and the anodic processes involve two consecutive electrochemical steps, comparably rate-controlling,

The electrochemical behaviour of oxygen and hydrogen peroxide on silver electrodes

Abstract The reduction of oxygen and the reduction and oxidation of hydrogen peroxide at silver electrodes is examined, with special reference to the side reactions involving the metal and its corrosion products.

Standard potentials of the sodium amalgam electrode at various temperatures, with related thermodynamic functions

Standard potentials of the sodium amalgam electrode were determined over the temperature range from 10 to 70 °C, and the standard thermodynamic functions at 25 °C for the sodium amalgam were derived. Activity coefficients for sodium in the amalgam were obtained at sodium mole fractions up to 0.01, over the temperature range from 25 to 70 °C.

Standard potentials of amalgam electrodes in aqueous solutions, temperature coefficients, and activity coefficients of metals in mercury

Chairman: J. Jordan (USA); Secretary: K. Izutsu (Japan); Titular Members: A. K. Covington (UK); J. Juillard (France); R. C. Kapoor (India); E. Pungor (Hungary); Associate Members: J. F. Coetzee (USA); W. Davison (UK); R. A. Durst (USA); M. Gross (France); H. Kao (China); K. M. Kadish (USA); R. Kalvoda (Czechoslovakia); Y. Marcus (Israel); T. Mussini (Italy); H. W. NUrnberg (FRG); M. Senda (Japan); D. E. Smith (USA); N. Tanaka (Japan); National Representatives: D. D. Perrin (Australia); B. Gilbert (Belgium); W. C. Purdy (Canada); R. Neeb (FRG); K. Tóth (Hungary); S. K. Rangarajan (India); W. F. Smyth (Ireland); E. Grushka (Israel); Z. Galus (Poland); G. Johansson (Sweden); J. Buffle (Switzerland); B. Birch (UK); J. Osteryoung (USA); M. Branica (Yugoslavia).