The reaction between monosilicic acid and aluminium hydroxide. I. Kinetics of adsorption of silicic acid by aluminium hydroxide

Soil Research ◽  
1967 ◽  
Vol 5 (2) ◽  
pp. 295 ◽  
Author(s):  
FJ Hingston ◽  
M Raupach
Keyword(s):  
Ionic Strength ◽  
Silicic Acid ◽  
Electrolyte Solution ◽  
Aluminium Hydroxide ◽  
Solid Phase ◽  
Supporting Electrolyte ◽  
Kcal Mole ◽  
Monosilicic Acid ◽  
Kinetics Of ◽  
Supporting Electrolyte Solution

Studies of the reaction between monosilicic acid and crystalline aluminium hydroxide showed that a number of layers of silicic acid could be formed on the surface of the hydroxide. Silicate is considered to be adsorbed as silicic acid rather than as silicate ions. The first layer was produced by rapid reaction of silicic acid with the surface of aluminium hydroxide. The isotherm for this initial reaction was not affected by varying the temperature from 10 to 35�C or by increasing the ionic strength of the supporting electrolyte solution. Adsorption of silicic acid resulted in increased KOH uptake by (or H2SO4 displacement from) the solid phase, which corresponded to a decrease in pH of the suspension. Subsequent layer formation was slower; the rate increased both with increasing temperature and with the ionic strength of the supporting electrolyte solution. Study of the kinetics of the reaction showed that these layers could have formed by polymerization of silicic acid on the hydroxide surface. The activation energy for the reaction increased with increasing surface coverage from 15 to 24 kcal/mole for the second layer and was about 24 kcal/mole for the third layer.

Analysis of the Electrode Kinetics of Ni(II) Reduction in Thiocyanate Media on the Dropping Mercury Electrode

2000 ◽  
Vol 65 (3) ◽  
pp. 326-342
Author(s):  
María S. Crespo-Pinilla ◽  
Fernando Mata-Pérez ◽  
Rosa M. Villamañán
Keyword(s):  
Ionic Strength ◽  
Compensation Effect ◽  
Supporting Electrolyte ◽  
Mercury Electrode ◽  
Electrode Kinetics ◽  
Surface Process ◽  
Experimental Conditions ◽  
Dropping Mercury Electrode ◽  
Kinetics Of

A study of two prewaves of the Ni(II)-SCN- system was carried out under the experimental conditions when the influence of electroreduction of SCN- is negligible. Kinetics of Ni(II) reduction in thiocyanate media on the dropping mercury electrode was studied by DC Tast Polarography (DCTP) via determination of Koutecký's parameter χ; the influence of different variables was analyzed. The study of prewaves was performed using various polarographic techniques. Values of χ depend on the SCN- concentration, pH, ionic strength (Ψ-effect) and on the nature of the supporting electrolyte. The number of electrons n, the transfer coefficient α, the stoichiometric number ν, ∆H≠, and ∆S≠ were determined (compensation effect). The first prewave has character of a reaction in the solution, the second prewave is a surface process. Main features of both mechanisms are common: catalytic nature, one-electron step discharge and the rate-determining process between species of opposite charges.

Kinetics of aquation of the fluoropentaamminecobalt(III) ion

1970 ◽  
Vol 48 (7) ◽  
pp. 1054-1058 ◽  
Author(s):  
T. W. Swaddle ◽  
W. E. Jones
Keyword(s):  
Ionic Strength ◽  
Rate Coefficient ◽  
Hydrogen Ion ◽  
Fluoride Ion ◽  
Kcal Mole ◽  
First Order ◽  
Order Rate ◽  
Relationship Of ◽  
The Relationship ◽  
Kinetics Of

The kinetics of the hydrogen-ion-independent pathway for the replacement of fluoride in aqueous (NH3)5CoF2+ by H2O have been reinvestigated using a specific fluoride-ion electrode, with due regard for the concomitant autocatalytic loss of the ammine ligands. In perchlorate media of ionic strength 0.1 M, the first-order rate coefficient is 1.22 × 10−6 s−1 at 45°, and the kinetics are represented by ΔH* = 24.4 kcal mole−1 and ΔS* = −9 cal deg−1 mole−1 over the range 35–75° at least. The relationship of these data to those for the aquation of other species of the type ML5Xn+ is discussed.

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 FORMATION OF THE MONO–FLUORO COMPLEX OF IRON (III) IN AQUEOUS SOLUTION

1960 ◽  
Vol 38 (4) ◽  
pp. 567-575 ◽  
Author(s):  
D. Pouli ◽  
W. MacF. Smith
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Temperature Interval ◽  
Kcal Mole ◽  
Entropy Of Activation ◽  
Fluoro Complex ◽  
Kinetics Of

The kinetics of the reactions involved in the formation of the mono–fluoro complex of iron (III) in aqueous solutions have been examined spectrophotometrically at ionic strength 0.5 and over the temperature interval 0.1 to 12.1 °C. The results are interpretable on the assumption that the following two reactions contribute significantly to the rate Fe+++ + F− = FeF++ and Fe+++ + HF = FeF++ + H+, the former having a heat of activation of 22.8 ± 2.5 kcal mole−1 and an entropy of activation of 35 ± 9 cal deg−1 mole−1, the latter having a heat of activation of 8.7 ± 0.7 kcal mole−1 and an entropy of activation of −24.5 ± 3 cal deg−1 mole−1.

THE KINETICS OF THE FORMATION OF THE MONOSULPHATO COMPLEX OF IRON (III) IN AQUEOUS SOLUTION

1962 ◽  
Vol 40 (9) ◽  
pp. 1836-1845 ◽  
Author(s):  
G. G. Davis ◽  
W. MacF. Smith
Keyword(s):  
Experimental Data ◽  
Aqueous Solution ◽  
Ionic Strength ◽  
Continuous Flow ◽  
Hydrogen Ions ◽  
Kcal Mole ◽  
Forward Reaction ◽  
First Order ◽  
Kinetics Of Formation ◽  
Kinetics Of

The kinetics of formation of the monosulphato complex of iron (III) has been examined spectrophotometrically using a continuous-flow technique over the range of temperatures 15.6 to 34.5 °C in an aqueous medium of ionic strength 0.5 and a range of concentrations of hydrogen ions 0.05 to 0.30 M. The experimental data may be interpreted on the assumption that the significant reactions are a bimolecular association opposed by a first-order dissociation [Formula: see text] For the forward reaction ΔH≠ is 18.0 kcal mole−1 and ΔS≠ is 19.4 cal mole−1 deg−1.

scholarly journals Cyclic Voltammetry of Auranofin

1999 ◽  
Vol 6 (4-5) ◽  
pp. 233-238 ◽  
Author(s):  
Ahmed A. Mohamed ◽  
Alice E. Bruce ◽  
Mitchell R. M. Bruce
Keyword(s):  
Cyclic Voltammetry ◽  
Electrolyte Solution ◽  
Supporting Electrolyte ◽  
Oxidation Processes ◽  
Irreversible Oxidation ◽  
Thiolate Complexes ◽  
Gold Thiolate ◽  
Oxidative Behavior ◽  
Supporting Electrolyte Solution ◽  
Repeated Cycling

The oxidative behavior of Auranofin, 2,3,4,6-tetra-O-acetyl-1-thio-β -D-glucopyranosato- S(triethylphosphine)gold(I), was investigated by using cyclic voltammetry (CV) in 0.1 M Bu4NPF6/CH2Cl2 and 0.1 M Bu4NPF4/CH2Cl2 solutions using Pt working and auxiliary electrodes and a Ag/AgCI reference. CV studies at scan rates from 50-2,000 mV/s and Auranofin concentrations between 1 and 4 mM, show two irreversible oxidation processes occurring at +1.1 V and +1.6 V vs. Ag/AgCl. Ph3PAu (p-thiocresolate) was also investigated as a reference for comparison of the oxidation processes in Auranofin to that of other phosphine gold thiolate complexes previously reported. The electrochemical response appears to be sensitive to adsorption at the electrode as well as to the nature of the supporting electrolyte solution. Repeated cycling shows a build up of products at the electrode.

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