TEMPERATURE COEFFICIENTS FOR SELF-DIFFUSION IN SOLUTION

1954 ◽  
Vol 32 (2) ◽  
pp. 71-78 ◽  
Author(s):  
C. J. Krauss ◽  
J. W. T. Spinks
Keyword(s):  
Activation Energy ◽  
Aqueous Solutions ◽  
Infinite Dilution ◽  
Kcal Mole ◽  
Self Diffusion ◽  
Temperature Coefficients ◽  
Sodium Dihydrogen

Coefficients of self-diffusion have been measured for aqueous solutions of sodium dihydrogen phosphates from 1 molar to 10−4 molar and at temperatures of 15, 25, 35, and 45 °C. The activation energy of self-diffusion has been calculated for various concentrations. It decreases from 5.4 kcal./mole at 0.9 M to 4.3 kcal./mole. at infinite dilution.

KINETICS OF THE OXIDATION OF URANIUM (IV) BY IRON (III) IN AQUEOUS SOLUTIONS OF PERCHLORIC ACID

1955 ◽  
Vol 33 (12) ◽  
pp. 1780-1791 ◽  
Author(s):  
R. H. Betts
Keyword(s):  
Electron Transfer ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Perchloric Acid ◽  
Rate Constants ◽  
Kcal Mole ◽  
Kinetics Of Oxidation ◽  
Temperature Coefficients ◽  
Kinetics Of ◽  
Rate Controlling Step

The kinetics of oxidation of uranium (IV) by iron (III) in aqueous solutions of perchloric acid have been investigated at four temperatures between 3.1 °C. and 24.8 °C. The reaction was followed by measurement of the amount of ferrous ion formed. For the conditions (H+) = 0.1–1.0 M, ionic strength = 1.02, (FeIII) = 10−4–10−5 M, and (UIV) = 10−4–10−5 M, the observed rate law is d(Fe2+)/dt = −2d(UIV)/dt[Formula: see text]K1 and K2 are the first hydrolysis constants for Fe3+ and U4+, respectively, and K′ and K″ are pseudo rate constants. At 24.8 °C., K′ = 2.98 sec.−1, and K″ = 10.6 mole liter−1 sec−1. The corresponding temperature coefficients are ΔH′ = 22.5 kcal./mole and ΔH″ = 24.2 kcal./mole. The kinetics of the process are consistent with a mechanism which involves, as a rate-controlling step, electron transfer between hydrolyzed ions.

The kinetics of the ordering process in triclinic NaAlSi3O8

1960 ◽  
Vol 32 (249) ◽  
pp. 436-454 ◽  
Author(s):  
J. D. C. McConnell ◽  
Duncan McKie
Keyword(s):  
Activation Energy ◽  
Kinetic Analysis ◽  
Vapour Pressure ◽  
Polymorphic Transformation ◽  
Water Vapour Pressure ◽  
Kcal Mole ◽  
Temperature Range ◽  
Self Diffusion ◽  
Dry Heating ◽  
Kinetics Of

SummaryA kinetic analysis is presented of the data of MacKenzie (1957) on the hydrothermal treatment of NaAlSi3O8 under isobaric, isothermal conditions in the temperature range 450° C. to 1000° C.The analysis indicates the existence of a smeared polymorphic transformation in the temperature range around 600° C. The activation energy for the transformation is about 60 kcal. mole−1 and has been equated with the process of self-diffusion involved in Al-Si ordering in the structure. Some dry-heating experiments and the influence of varying water vapour pressure are discussed.

MEASUREMENTS OF SELF-DIFFUSION IN AQUEOUS SOLUTIONS OF SODIUM DIHYDROGEN PHOSPHATE

1952 ◽  
Vol 30 (4) ◽  
pp. 311-319 ◽  
Author(s):  
J. E. Burkell ◽  
J. W. T. Spinks
Keyword(s):  
Aqueous Solutions ◽  
The Self ◽  
Dihydrogen Phosphate ◽  
Sodium Dihydrogen Phosphate ◽  
Original Activity ◽  
Self Diffusion ◽  
Iodide Solution ◽  
Measured Length ◽  
Similar Solutions ◽  
Sodium Dihydrogen

Measurements of self-diffusion in aqueous solutions of sodium dihydrogen phosphate have been made using P32 as tracer. The method involves the preparation of two similar solutions differing only in the fact that one is "labelled" by means of the P32 isotope. A capillary cell is filled with the radioactive solution and immersed in a relatively large volume of inactive solution, maintained at a constant temperature. After diffusion has proceeded for a measured length of time, the cell is removed and the radioactivity of the liquid remaining in it measured by counting. The self-diffusion coefficient may be calculated from the length of the capillary cell, the period of diffusion, and the ratio of the final activity to the original activity. The method was checked by repeating some work on the self-diffusion of Na+ in sodium iodide solution. Self-diffusion measurements were made with sodium dihydrogen phosphate solutions of several concentrations between 1.0 and 10−4 molar.

Proton NMR Study of Molecular Motions in the Solid Phase of a Smectic A Liquid Crystal

1975 ◽  
Vol 53 (17) ◽  
pp. 1646-1650 ◽  
Author(s):  
Ronald Y. Dong ◽  
M. Wiszniewska ◽  
E. Tomchuk ◽  
E. Bock
Keyword(s):  
Activation Energy ◽  
Liquid Crystal ◽  
Molecular Motion ◽  
Solid Phase ◽  
Methyl Groups ◽  
Molecular Motions ◽  
Kcal Mole ◽  
Self Diffusion ◽  
Smectic A ◽  
Nmr Study

Proton T1, T1ρ, and T1D were studied in the solid phase of diethylazoxybenzoate from 105 K to the melting point. The activation energies for the threefold reorientation of methyl groups and for the molecular self-diffusion were determined to be about 3.3 and 11 kcal/mole respectively. Between 170 and 240 K, a new slow molecular motion with an estimated activation energy of 3.7 kcal/mole was detected via the T1ρ data.

scholarly journals Self-Diffusion Coefficients, Aggregation Numbers and the Range of Existence of Spherical Micelles of Oxyethylated Alkylphenols

2021 ◽  
Author(s):  
Victor P. Arkhipov ◽  
Natalia A. Kuzina ◽  
Andrei Filippov
Keyword(s):  
Aqueous Solutions ◽  
Diffusion Coefficients ◽  
The Self ◽  
Self Diffusion ◽  
Aggregation Numbers ◽  
Temperature Ranges ◽  
Spherical Micelles ◽  
Limiting Values

AbstractAggregation numbers were calculated based on measurements of the self-diffusion coefficients, the effective hydrodynamic radii of micelles and aggregates of oxyethylated alkylphenols in aqueous solutions. On the assumption that the radii of spherical micelles are equal to the lengths of fully extended neonol molecules, the limiting values of aggregation numbers corresponding to spherically shaped neonol micelles were calculated. The concentration and temperature ranges under which spherical micelles of neonols are formed were determined.

scholarly journals Surface Thermodynamics, Viscosity, Activation Energy of N-Methyldiethanolamine Aqueous Solutions Promoted by Tetramethylammonium Arginate

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1337
Author(s):  
Xiangfeng Tian ◽  
Lemeng Wang ◽  
Pan Zhang ◽  
Dong Fu
Keyword(s):  
Activation Energy ◽  
Surface Tension ◽  
Diffusion Coefficient ◽  
Aqueous Solutions ◽  
Quantitative Relationship ◽  
Viscosity Data ◽  
Surface Thermodynamics ◽  
Surface Entropy ◽  
Operation Conditions ◽  
Surface Enthalpy

The surface tension and viscosity values of N-methyldiethanolamine (MDEA) aqueous solutions promoted by tetramethylammonium arginate ([N1111][Arg]) were measured and modeled. The experimental temperatures were 303.2 to 323.2 K. The mass fractions of MDEA (wMDEA) and [N1111][Arg] (w[N1111][Arg]) were 0.300 to 0.500 and 0.025 to 0.075, respectively. The measured surface tension and viscosity values were satisfactorily fitted to thermodynamic models. With the aid of experimentally viscosity data, the activation energy (Ea) and H2S diffusion coefficient (DH2S) of MDEA-[N1111][Arg] aqueous solution were deduced. The surface entropy and surface enthalpy of the solutions were calculated using the fitted model of the surface tension. The quantitative relationship between the calculated values (surface tension, surface entropy, surface enthalpy, viscosity, activation energy, and H2S diffusion coefficient) and the operation conditions (mass fraction and temperature) was demonstrated.

The contribution of friction stress to the creep behaviour of the nickel-base in situ composite, γ—γ'-Cr 3 C 2

1980 ◽  
Vol 373 (1752) ◽  
pp. 93-109 ◽  
Keyword(s):  
Activation Energy ◽  
Creep Behaviour ◽  
Friction Stress ◽  
Matrix Alloy ◽  
Dislocation Motion ◽  
Self Diffusion ◽  
The Matrix ◽  
Nickel Base ◽  
Distribution Of Stress

Transient creep following stress reductions has been analysed by the method described by McLean (1980) to determine the friction stress σ 0 as a function of temperature and directional solidification conditions for the γ-γ'-Cr 3 Cr 2 in-situ composite and for the γ-γ' matrix alloy. These values of σ 0 are identical to the flow stresses at creep strain rates and can be identified with the sums of the barriers to dislocation motion through the matrix by climb around γ'-particles and Orowan bowing between the carbide fibres. The friction stress and the kinetics of deformation of the composite are determined by the matrix behaviour, whereas its creep strength depends on the distribution of stress between fibre and matrix. When the steady-state creep behaviour of γ-γ'-Cr 3 C 2 is analysed by using the usual power law description in terms of the effective stress σ — σ 0 , rather than the applied stress σ, the stress exponent is ca 4 and the activation energy is similar to the activation energy of self-diffusion for nickel. The results provide strong evidence for the operation of recovery-creep in both the composite and matrix alloys.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

Doping Effect in Nickel Oxide

2009 ◽  
Vol 289-292 ◽  
pp. 775-782 ◽  
Author(s):  
Zbigniew Jurasz ◽  
Krzysztof Adamaszek ◽  
Romuald Janik ◽  
Zbigniew Grzesik ◽  
Stanisław Mrowec
Keyword(s):  
Activation Energy ◽  
Nickel Oxide ◽  
High Temperatures ◽  
Oxygen Pressure ◽  
Pressure Dependence ◽  
Oxidation Rate ◽  
Doping Effect ◽  
Self Diffusion ◽  
Electron Holes ◽  
Influence Of Impurities

Detailed investigations of nonstoichiometry as well as chemical and self-diffusion in nickel oxide have shown that doubly ionised cation vacancies and electron holes are the predominant defects in this material. The present work is an attempt to demonstrate that aliovalent impurities (Cr, Al, Na and Li) may considerably influence the concentration of these defects and, consequently, the oxidation rate of nickel at high temperatures. It has been shown that small amounts of tri-valent impurities (Cr, Al) bring about an increase of the oxidation rate, while mono-valent ones (Li, Na) decrease the rate of oxidation. These phenomena may satisfactorily be explained in terms of a doping effect. All experiments have been carried out as a function of temperature (1373-1673 K) and oxygen pressure (1-105 Pa) and consequently, it was possible to determine the influence of impurities not only on the oxidation rate but also on the activation energy of reaction and its pressure dependence. The results of these investigations could again be elucidated in terms of doping effect.

The slow oxidation of methane

1956 ◽  
Vol 235 (1201) ◽  
pp. 158-173 ◽  
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Induction Period ◽  
Hydrofluoric Acid ◽  
Pressure Rise ◽  
Pressure Change ◽  
Kcal Mole ◽  
Gaseous Products ◽  
Oxidation Of Methane ◽  
Reproducible Manner

Mixtures of methane and oxygen behave in a reproducible manner at temperatures of 440 to 520°C and initial pressures of 100 to 350 mm when reacting in Pyrex vessels freshly cleaned with hydrofluoric acid. The apparent order of the reaction ranged from 2∙3 to 2∙6 and the overall activation energy from 29 to 41 kcal/mole. Analyses of the products formed have been made, together with measurements of pressure change. Formaldehyde is formed from the commencement of the reaction including the induction period, but its concentra­tion reaches a maximum near the stage where the pressure rise is a maximum, and then falls off. Hydrogen peroxide is also formed, less rapidly in the earliest stage, but its rate of formation overtakes that of formaldehyde and it reaches an even higher concentration. No other peroxides were detected, nor was methanol found. Hydrogen was present in the gaseous products. These observations are not in full accord with some of the conclusions derived from earlier investigations.

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