A computer method for the calculation of enthalpy changes for ion association in solution from calorimetric data

A general method for the determination of enthalpy changes in solution for systems containing an unlimited number of components, that can give rise to mononuclear, polynuclear, protonated, hydroxo and mixed species was set up.A computer program, DOEC, able to elaborate data on a calorimetric titration such as concentrations, changes to the mole number of the various species, solution ionic strength and reaction enthalpy was written. The program can also correct the ionic strength changes, that can occur during a titration. Thanks to the analogy of the mathematical expressions, the program can also be used for the treatment of spectrophotometric data.     

Experimental evidence for the existence of a Ramsauer—Townsend minimum in liquid CH4 and liquid Ar (Kr and Xe)

Experimental evidence for the existence of a Ramsauer—Townsend minimum in the electron scattering cross section for liquid CH₄ and liquid Ar (Kr and Xe) is provided from: (i) comparisons of thermal electron mobilities in gases with those in liquids, (ii) changes in the electron mobility with gas density, and (iii) the dependence of the electron mobility on temperature for liquids whose V₀, the energy of the electron state in the liquid, is ? 0 eV.     

Charge distribution in the nitrate ion

The difference electron density in the nitrate ion is studied by comparison of some Hartree-Fock-Slater calculations. It is shown that good qualitative agreement with experiment is obtained.     

Activation of CH bonds by transition metals : V. A study of the mechanism of metallation reactions of benzyl- and meta-fluorobenzylphosphines with RhI,IrI, PdII and PtII compounds

Reaction of R₂PCH₂C₆H₅ (R = cyclohexyl or t-butyl) with [(COT)₂RhCl]₂, [(COT)₂IrCl]₂, PdCl₂ or PtCl₂(benzonitrile)₂ yields cyclometallated compounds. The reactivity appears to decrease in the order Ir^I ρ Rh^I ρ ρ Pd^II ≈ Pt^II, suggesting a different reaction mechanism for univalent and bivalent d⁸ metal atoms. Reaction of meta-FC₆H₄CH₂PR₂ with the same metal chlorides shows that for Rh^I and Ir^I a nucleophilic mechanism operates and for Pd^II an electrophilic one. For Pt^II no decision could be made on the basis of these experiments. Steric effects have a large influence on the rates of the reactions.     

The investigation of the adsorptive behaviour of electroactive species by means of admittance analysis: Part II. Anion-induced adsorption of cadmium(II) from bromide and iodide solutions at the dropping mercury electrode

The adsorption of Cd(II) has been studied by measuring the interfacial admittance spectra at different dc potentials of the dropping mercury electrode (DME) in solutions of: (a) 1 M KBr+0.48 mM Cd(NO₃)₂,(b) 1 M KI+0.105 mM CdI₂ and (c) 0.1 M NaI+0.9 M NaClO₄ +0.116 mM CdI₂ The experimental data were analysed using the procedures described in Part I of this series. The frequency dependence of the admittance corresponds to that of a reversible electrode reaction with reactant adsorption. The potential dependence of the resulting adsorption parameters can be mathematically described by a Langmuir isotherm for adsorption of Cd(II) with the adsorption energy being at least a quadratic function of potential. Detailed checks on the consistency of this model have been applied and were found to be satisfactory.     

Modulation of the ENDOR spectrum of gamma-irradiated sucrose by lattice vibrations

The temperature variation of the matrix ENDOR linewidth of γ-irradiated sucrose is interpreted as being due to the modulation of the dipolar electron spin-proton interactions by lattice vibrations. Two separate proton populations can be distinguished, they are respectively identified as the protons on the pyranose ring and those on the furanose ring.     

The detection of ignition temperatures of various materials by photothermal analysis

The ignition temperatures of various common materials were detected by means of a photothermal analysis apparatus. The sample is heated in a tube furnace which is programmed at a linear heating rate; a photomultiplier tube located at the end of the furnace tube is used to detect the ignition process. This technique is potentially useful and is most advantageous when used to supplement DTA or TG data. The instrumental factors which influence the ignition temperature, such as heating rate, furnace atmosphere, and so on. were investigated. Factors such as the sample surface area, mass. density, and others can affect the reproducibility of the curves even if the instrumental factors are held constant.     

The properties of the ion associates of benzophenone in DMF

The properties of the ion associates of benzophenone (BP) free radicals with Na⁺ and Li⁺ have been investigated polarographically in dimethylformamide. It was found that BP^? forms ion pairs with Na⁺ (K_ass=69 M^?1) and two types of associates with Li⁺: BP^?...Li⁺ (K_ass,1=330 M^?1) and BP^?...(Li⁺)₂(K_ass,2M^?2). The influence of temperature on the equilibria was also discussed. The ion associates with Li⁺ disappear in a disproportionation reaction; the mechanism and kinetics of that reaction were studied. It was found that the main contribution to the overall kinetics are made by the pairs (a) BP^?...Li⁺+BP^?...Li⁺, (b) BP^?+BP^?...(Li⁺)₂ (c) BP^?...Li⁺+BP^?...(Li⁺)₂.     

The system copper-tellurium

The system copper-tellurium was investigated by DTA, DSC, and X-ray methods. A phase diagram with the phases Cu_2?xTe (33.5–36.2 mole% Te), Cu_3?xTe₂ (40–41 mole%), and CuTe was constructed. In the homogeneity ranges of the nonstoichiometric phases several superstructures were observed. The lattice parameters and d values of some of these phases are given.     

Thermoanalytical studies of reactions in solid mixtures of pentaerythritol and oxidizing agents. I. Potassium dichromate and potassium permanganate

DSC and TG, supported by IR spectrophotometry and gas chromatography, were applied to the study of reactions in solid mixtures of pentaerythritol (PE), 2,2-bis-(hydroxymethyl)-1,3-propanediol, and the oxidizing agents potassium dichromate and potassium permanganate. The results indicate that esterification followed by decarbonylation occurred when the mole ratio of oxidizing agent to PE was equal to or greater than 5 : 1. At lower mole ratios evidence for esterification followed by the formation of cyclic acetal intermediates was obtained.     

Ab initio calculation of distortion and bonding energy components of the cis-trans conversion energy for formic,thiolformic and thionformic acids

The energy change in the formation of the intramolecular hydrogen-bonded ring conformers of formic, thiolformic and thionformic acids from the chain conformers has been divided up into distortion and bonding energy components, following the treatment of Smit, Derissen, and van Duijneveldt for the formation of the formic acid dimer.     

Chronopotentiometric studies of the tetrabutylammonium ion transfer from water to 1,2-dichloroethane

Electrochemically reduced graphite in contact with tetralkylammonium ions/DMF may react with electrophiles either as a nucleophile or as a reducing reagent. The reaction at the interface or at the immediately accessible active centres of the crystal causes some modification of the structure, which is studied here. This method allows the formation of polybutylated or poly-carboxylated graphite and may lead to other modified crystals of great interest for building modified electrodes.     

Polymerization of acrylonitrile initiated by the redox system peroxydisulphate-isoamyl alcohol catalyzed by silver ion

The polymerization of acrylonitrile in aqueous media initiated by peroxydisulphate-isoamyl alcohol(IAA) redox pair catalyzed by silver ion was studied at low conversion. The polymerization had kinetic orders 1.5 with respect to monomer, 0.6 (peroxydisulphate) and 0.5 (silver ion). The reactions were carried out at various temperatures and the overall activation energy was found to be 5.5 kcal/mol. The effect of certain water-miscible organic solvents was also investigated. A mechanism of initiation is tentatively proposed.     

Configuration interaction satellites in the ESCA spectra of thorium and other actinide compounds

ESCA spectra of the Th 4d, 4f, 5s, 5p and 5d core levels have been recorded in ThF₄, Th(AcAc)₄ and other Th complexes. In addition to weak 4f and 5d satellites which are normally considered to be shake up satellites, a number of unusual satellites have been characterized in these compounds. In particular, the intense 5p_3/2 satellites, as well as previous similar 5p_{$\text{3}\text{2}$} satellites in other actinides, are shown to be due to configuration interaction of the 5p hole state with a 5d² hole state. Similarly, the 4d_{$\text{5}\text{2}$}, 5s and additional 5d satellites are probably also due to configuration interaction.     

Bromine Hyperfine and quadrupole fine structure in the MODR spectrum of sym-tetrabromobenzene in its lowest triplet state

Bromine hyperfine and quadrupole fine structure has been observed in the 3 cm MODR spectrum of the photoexcited ³B_1u state of symmetric tetrabromobenzene (s?TBB) in a durene host crystal at liquid helium temperature. A preliminary analysis of the observed structure yields the two in-plane values of the bromine hyperfine tensor |A_y/gβl = 10.3 and |A_z/gβ| = 16.5 (for ⁸¹Br), and a comparison of these values with those recently observed for the α-bromomaleic acid radical suggests that the correct zero-field scheme in the lowest triplet state of s-TBB is τ_N > τ_M > τ_L.