The thermodynamics of aqueous borate solutions I. Mixtures of boric acid with sodium or potassium borate and chloride

Potentials for the cell without liquid junction where M is sodium or potassium are reported over a range of ionic strength to I=3 mol-kg^–1 at 5 to 55°C. Total boron concentration in the solutions was restricted to low levels to minimize formation of polynuclear boron species. Cell potentials are treated with the Pitzer ion interaction treatment for mixed electrolytes, with linear ionic strength dependence assumed for the activity coefficient of undissociated boric acid. Trace activity coefficients of sodium and potassium borates in chloride media are calculated at various temperatures.     

Complexation of aluminate anion by bis-tris in aqueous media at 25–50°C

Gibbsite, Al(OH)₃, solubility studies in aqueous NaCl solutions at pH 9 demonstrate that the aluminate anion forms a strong complex with the neutral Bis-tris molecule 2,2-Bis(hydroxymethyl)-2,2,2-nitrilotriethanol, at low temperatures. The logarithm of the molal concentration quotient for the reaction

Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C

The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO₃, KBr, KI, KNO₃, CaCl₂, SrCl₂, BaCl₂, Li₂SO₄, K₂SO₄, Mn(NO₃)₃)] as a function of concentration at 25°C. The solubilities, mol (kg-H₂O)^–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg^–1)

Oxidation of chromium(III) by alkaline hexacyanoferrate(III)

Alkaline hexacyanoferrate(III) oxidation of freshly prepared solutions of Cr^III (pH>12) at 27°C follows the rate law, Equation 1:

Kinetics and mechanism of osmium(VIII)-catalyzed oxidation of hypophosphite by hexacyanoferrate(III) in aqueous alkali

The kinetics of osmium(VIII)-catalyzed oxidation of hypophosphite with hexacyanoferrate(III) in alkaline medium has been studied. The rate is independent of the concentration of the oxidant. The order with respect to hydroxide ion is variable. Rate law (1) conforms with the experimental observations.

Mechanism of the Reaction of Xenon Tetraoxide with Hydrogen: A Photochemical Reaction

The dependence of the rate of a photochemical reaction of XeO₄with H₂on the concentrations of H₂and the diluent gases He and CO₂is studied at room temperature. The results are compared with the data for the dark reaction. A mechanism with the elementary energetic branched-chain reaction OH (v) + XeO₄OH + O + XeO₃is proposed to explain the results of the study.     

O-H ... O(S) hydrogen bonds in 2-hydroxy(thio)benzamides. Survey of spectroscopic and structural data

Summary From a survey of spectroscopic and structural data of six corresponding 2-hydroxybenzamides and 2-hydroxythiobenzamides (amide, N-methylamide, N,N-dimethylamide, piperidide, morpholide, 2,6-dimethylpiperidide) remarkable similarities between O(N)-H ... O and O(N)-H ... S hydrogen-bonds are obtained, concerning both, hydrogen-bond patterns and hydrogen-bond strengths. In dilute solution the OH groups of all compounds are intramolecularly associated to the (thio)carbonyl O (S) atoms with distinctly larger hydrogen-bond strengths for primary and secondary amides [ (O-H)=2950–3020 cm^–1, (OH)=12.16–11.99 ppm] and thioamides [ (O-H)=2960–3000 cm^–1, (OH)=11.65–11.13 ppm], than for tertiary amides [ (O-H)=3200–3250 cm^–1, (OH)=9.95–8.95 ppm] and thioamides [ (O-H)=3245–3330 cm^–1, (OH)=8.09–7.06 ppm]. In the solid state, the OH groups of the primary and secondary (thio)amides are also engaged in rather strong intramolecular O-H ... O=C [O ... O=2.51 Å, (O-H)=2700–2750 cm^–1] and O-H ... S=C [O ... S=2.90–2.94 Å, (O-H)=2700–2840 cm^–1] hydrogen-bonds; thetrans-NH groups of the primary (thio)amides and the NH groups of the secondary (thio)amides connect the molecules to N-H ... O-H [N ... O=2.93–3.10 Å, (N-H)=3319–3407 cm^–1] hydrogen-bonded chains; the remainingcis-NH groups of the primary (thio)amides give rise to eight-membered cyclic dimers via N-H ... O=C [N ... O=2.93 Å, (N-H)=3226 cm^–1] and N-H ... S=C [N ... S=3.46–3.47 Å, (N-H)=3233–3277 cm^–1] hydrogen-bonds. Contrary, the OH groups of the tertiary (thio)amides are intermolecular associated in the solid state and link the molecules to O-H ... O=C [O ... O=2.63–2.75 Å, (O-H)=3075–3135 cm^–1] and O-H ... S=C [O ... S=3.18–3.26 Å, (O-H)=3130–3190 cm^–1] hydrogen-bonded chains.

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O-H ... O(S)-Wasserstoffbrückenbindungen in 2-Hydroxy(thio)benzamiden. Ein Überblick über spektroskopische und strukturelle Daten

Zusammenfassung Aus einer Zusammenstellung von spektroskopischen und strukturellen Daten von sechs entsprechenden 2-Hydroxybenzamiden und 2-Hydroxythiobenzamiden (Amid, N-Methylamid, N,N-Dimethylamid, Piperidid, Morpholid, 2,6-Dimethylpiperidid) ergeben sich bemerkenswerte Analogien zwischen O(N)-H ... O und O(N)-H ... S H-Brücken, die sowohl die H-Brücken-Muster als auch die H-Brücken-Stärken betreffen. In verdünnter Lösung sind die OH-Gruppen aller Verbindungen intramolekular mit den O(S)-Atomen der (Thio)Carbonylgruppen assoziiert, wobei die H-Brücken bei den primären und sekundären Amiden [ (O-H)=2950–3020 cm^–1, (OH)=12.16–11.99 ppm] und Thioamiden [ (O-H)=2960–3060 cm^–1, (OH)=11.65–11.13 ppm] deutlich stärker sind, als bei den tertiären Amiden [ (O-H)=3200–3250 cm^–1, (OH)=9.95–8.95 ppm] und Thioamiden [ (O-H)=3245–3330 cm^–1, (OH)=8.09–7.06 ppm]. Im Festkörper weisen die primären und sekundären (Thio)Amide ebenfalls sehr starke intramolekulare O-H ... O=C [O ... O=2.51 Å, (O-H)=2700–2750 cm^–1] und O-H ... S=C [O ... S=2.90–2.94 Å, (O-H)=2700–2840 cm^–1] H-Brücken auf; dietrans-NH-Gruppen der primären (Thio)Amide und die NH-Gruppen der sekundären (Thio)Amide verknüpfen die Moleküle über N-H ... O-H H-Brücken [N ... O=2.93–3.10 Å, (N-H)=3318–3407 cm^–1] zu Ketten; die verbleibendencis-NH-Gruppen der primären (Thio)Amide bilden zyklische, über N-H ... O=C [N ... O=2.93 Å, (N-H)=3226 cm^–1] und N-H ... S=C [N ... S=3.46–3.47 Å, (N-H)=3233–3277 cm^–1] H-Brücken gebundene, 8-Ring-Dimere. Im Gegensatz dazu sind die OH-Gruppen der tertiären (Thio)Amide im Festkörper intermolekular assoziiert und verknüpfen die Moleküle über O-H ... O=C [O ... O=2.63–2.75 Å, (O-H)=3075–3135 cm^–1] und O-H ... S=C [O ... S=3.18–3.26 Å, (O-H)=3130–3190 cm^–1] H-Brücken zu Ketten.

     

Bimolecular Reactions of Radical Generation Involving Nitrogen-Containing Compounds with Multiple Bonds

Retrodisproportionation reactions R"C=NR" + HY R" NHR" + , RCN + HY R =NH + , RN=NR + HY R NHR + , RNO + HY R OH + , and RNO₂ + HY RN( )OH + (where HY represents hydrocarbons, alcohols, phenols, amines, thiophenols, etc.) are considered as sources of radical generation. The enthalpies of these reactions are calculated. The parabolic model is used to calculate the rate constants for 254 such reactions. Various HY compounds acting as hydrogen-atom donors are compared with nitrogen-containing compounds acting as hydrogen-atom acceptors. The PhN(O) and PhNO₂ compounds exhibit the highest activity among the studied acceptors.     

Reactions of alkoxy and hydroxy radicals generated photochemically from hydroperoxide molecules

In the present work as well as HRO^. radicals were generated in the photochemical interaction of 1,2-benzanthracene with -ethyl phenyl hydroperoxide /HROOH/ in C₆H₆ and CCl₄ at 304 K. radicals were trapped by C₆H₆. The main reaction of HRO^. radicals is hydrogen abstraction from the hydroperoxide group of HROOH. Although OH radicals are less selective, the hydrogen abstraction is the main process during their interaction with aromatics in contrast to reactions in aqueous solutions, where addition to the benzene ring is the rate-determining process in CCl₄:

Kinetics and mechanism of oxidation of hydroxylamine by tetrachloroaurate(III) ion

The oxidation of H₂NOH is first-order both in [NH₃OH⁺] and [AuCl₄ ^–]. The rate is increased by the increase in [Cl^–] and decreased with increase in [H⁺]. The stoichiometry ratio, [NH₃OH⁺]/[AuCl₄ ^–], is 1. The mechanism consists of the following reactions.

On Acyclic Molecular Graphs with Prescribed Numbers of Edges that Connect Vertices with given Degrees

We find a necessary and sufficient conditions on a sequence

Some analytical results forABC,ABCD, andXBCD coupled spin 1/2 systems. I

By choosing a suitable linear combination of the constants of the motion , it is shown that the calculation of the density matrix(t) can be simplified by subdividing the Hamiltonian into . In particular, this technique can be used to obtain closed form solutions for the eigenfunctions and eigenvalues of spin 1/2ABC andXBCD spin systems, evolving in the presence of Zeeman offsets, scalar coupling and dipolar interactions. In general, the eigenvalues and eigenvalues of are very transparent, while those of require more effort. Nevertheless, simplifications can be made. Firstly, the effective size of the Hamiltonian matrix which needs to be considered, is reduced fromN ×N to at least (N – 2) × (N – 2), while forXBC ... systems it is reduced to (N – 4) × (N – 4). Secondly, the highest rank and highest/lowest order tensor operators available to the spin ensemble are constants of the motion under . Finally, by exploiting the fact that is a good quantum number, it is possible to block-diagonalize the matrix into no more than 3 × 3 matrices.     

Thermodynamic Study of the NaCl + Na2SO4 + H2O System by Emf Measurements at Four Temperatures

Activity coefficients for sodium chloride in the NaCl + Na₂SO₄ + H₂O ternary system were determined from emf measurements of the cell

Effect of solvent on the partial molal volumes and heat capacities of nonelectrolytes

Group contributions to in seven solvents and to in three solvents have been tabulated. The variation of group parameters is discussed in terms of the solvent compressibility coefficient, _T. The scaled particle theory (SPT) is used to calculate cavity contributions to and C _p2 ^o . Interaction contributions are obtained from the cavity terms and and values estimated through the additivity schemes. values are more sensitive to solute-solvent interactions than in water and less sensitive in methanol. The SPT results for heat capacities support the concept of structural promotion by hydrophobic solutes in water.     

Alkaline hydrolysis of Co(Asn)2 (Asn = l-asparagine)

The kinetics of alkaline hydrolysis of Co(Asn)2, yielding Co(OH)2, NH3 and aspartic acid, have been studied spectrophotometrically, and the effects of CoII and NaOH concentrations on the reaction rate determined. The rate increases with increasing [NaOH], whereas variation of [CoII] has no significant effect. The kinetics of NH3 evolution conform to the rate law:

Parametric analysis of kinetic models. I. The simplest autocatalytic oscillator

A series of mechanisms allowing oscillations and differring in the form of their buffer steps (step 3)

Untersuchungen der Hydroxylammonium-Fluorozirconate(IV)

Summary Hydroxylammonium fluorozirconates have been investigated. Two new microcristalline phases have been isolated from aqueous solutions: (NH₃OH)₂ZrF₆ (1) and (NH₃OH)₃ZrF₇ (2). The crystals were prepared by slow evaporation of the solution of NH₂OH, Zr, and HF. Different compositions of the crystals were achieved by varying the molar ratios of the components. They were characterized by thermal analysis, vibrational spectroscopy, and structure (single crystal x-ray methods). (NH₃OH)₂ZrF₆ (1) crystallizes triclinic, P (No.: 2),a=7.400(2),b=7.609(2),c=7.887(2) Å, =57.29(3)°, =62.16(3)°, =67.83(2)°. (NH₃OH)₃ZrF₇ (2) crystallizes triclinic, P (No.: 2),a=7.128(1),b=7.989(1),c=8.888(1) Å, =109.72(1)°, =91.01(1)°, =104.27(1)°.

     

Dynamics of H+O2 collisions on anab initio potential energy surface

The dynamics of elementary rate processes for H+O₂ collisions on an ab initio potential energy surface have been simulated by quasiclassical trajectory theory (QCT). For H+O₂ (v=0,j=1), we have obtained the reaction probabilityP _r (E,b) as a function of collision energy E and impact parameterb, the reaction cross sectionS _r as a function ofE, and the average values of the product quantum numbers of OH.For H+0₂ (v=2,j=1, 20, 40, 60, 80, 100;v=1, 3, 4, 5,j=1) atE=0.3 eV, we have found thatb _max is about 4.5a ₀ and the impact parameter at whichP _r is maximum decreases asj increases. The reaction cross section increases asj andv become large. For inelastic collisions, whenb is small andj is large, the and are both small. For reactive collisions, almost equals zero, but the probability of being larger than zero increases with increasingj; and¯v _OH even shows population inversion forj=100. Additional details of the dynamics are shown in figures of interparticle distance and stereographs.     

Handling multicomponent systems in \mathbb{R}^n. I: Theoretical results

The phases of multicomponent systems (mixtures, states, etc.) containing the compounds are , where and . For (quaternary or higher dimensional systems), the displaying methods and visual investigations in the dimensional Euclidean space are tangentially or not at all described in the literature. In this paper we first develop the theoretical (both mathematical and computational) background in any dimension in . We focus not only on the important points, lines, surfaces of these systems, and computing method of the states of some processes in such systems, but also on the approximating methods of the above mentioned lines and surfaces, and, finally, on the question which is the region where a state (a point) falls into. Using the above results a computer program for PC's was created for evaluating and displaying the approximated surfaces. This program is described in I. Szalkai, SALT3DIM.exe – A program for handling 4 component mixtures, Preprint No. 047, University of Veszprém (1996), and the computing results are planned to be published in a forthcoming paper (I. Szalkai, Handling multicomponent systems in . II: Computational results, J. Chem. Inf. Comput. Sci., submitted).     

Characterization of Potassium Chloride as an Equitransferent “Intersolvental” Salt Bridge

The electromotive forces (emf) E _A and E _C of the following concentration cells with transference: respectively, together with the emfs E _MAX of the corresponding double cell without transference: have been measured at KCl molalities m (m ₁ fixed and m ₂ varied, with m ₂>m ₁) approximately up to the KCl solubility limit in 12 solvent mixtures for the three aqueous–organic solvent systems (ethylene glycol+water), (acetonitrile + water), and (1,4-dioxane + water) up to 0.8 mass fraction of organic component. For all the cases explored, the E _A vs. E _MAX relation is linear over the whole KCl molality range. The ionic transference numbers t of KCl determined therefrom show a curvilinear dependence on the mass fraction of the organic component of the relevant solvent mixture and are found to fall in the range 0.52–0.48, viz., within ±4% of exact equitransference (t ₊ = t _– = 0.5). In particular, KCl becomes exactly equitransferent (i.e., an ideal salt bridge) in aqueous mixtures with the following mass fractions of organic component: 0.4 ethylene glycol and 0.09 acetonitrile, as well as 0.12 methanol, and 0.08 and 0.34 ethanol from our recent work. Even if use of KCl as a salt bridge would be somewhat restricted by its limited solubility in high mass fractions of dioxane and acetonitrile and pending extension of investigation to other mixed-solvent systems, the above figures characterize KCl as a fairly good intersolvental salt bridge in electrochemistry, electroanalysis, and corrosion science.