Showing papers on "Equilibrium constant published in 1971"
268 citations
TL;DR: Electrical relaxation experiments have been performed with phosphatidylinositol bilayer membranes in the presence of the ion carrier valinomycin, and the equilibrium constant of the heterogeneous association reaction M(+) (solution) + S (membrane) --> MS(+) (memBRane) is found to be approximately 1 M(-1), about 10(6) times smaller than the association constant in ethanolic solution.
215 citations
TL;DR: In this paper, the sulfide fractionation factors involving pairs of pyrite, pyrrhotite, sphalerite, chalcopyrite and galena have been determined experimentally over the temperature range 250 °C to 600 °C.
Abstract: Sulfur isotopic fractionation factors involving pairs of pyrite, pyrrhotite, sphalerite, chalcopyrite, and galena have been determined experimentally over the temperature range 250 °C to 600 °C.Since chalcopyrite and pyrrhotite are not stable at higher PS2 conditions, buffer assemblages were necessary to control PS2 in experiments with these minerals. Since low PS2 values and low temperatures are unfavorable to rapid isotope exchange, techniques were devised whereby equilibrium constants could be estimated indirectly in systems where direct measurements are not possible because of the time factor.Current data place the sulfide minerals in the following order of 34S enrichment under equilibrium exchange conditions: pyrite > (pyrrhotite sphalerite) > chalcopyrite > galena in agreement with theoretical predictions. In agreement with theory the equilibrium exchange constant K for a given mineral pair depends upon temperature as follows: 1000 ln , where A denotes a constant. The A values for various mineral pa...
213 citations
Book•
01 Jan 1971TL;DR: The most important thermodynamic quantity for the practicing chemist is the Gibbs free-energy change, ΔG, which accompanies any reaction as mentioned in this paper, which can be calculated from the standard free energy of formation, δGf, of the species involved.
Abstract: The most important thermodynamic quantity for the practicing chemist is the Gibbs free-energy change, ΔG, which accompanies any reaction. This can be calculated from the standard free energy of formation, ΔGf, of the species involved. Unfortunately, this quantity is found scattered throughout the chemical literature. and presented using many conventions.This book provides a standard reference for chemists, particularly in the field of high temperature chemistry, solid state research, and materials research. The author has assembled in the form of charts and tables published free-energy data for binary compounds of the metals with the gaseous nonmetallic elements hydrogen, nitrogen, oxygen, sulfur, fluorine, and chlorine. In addition he has collected new data on the metal bromides, iodides, selenides, and tellurides, as well as on the vaporization of the elements, molecular dissociation of the gaseous elements, and ionization of the elements.Plastic overlays and scales are provided that can be used to read the composition of reacting gases, equilibrium constants, EMF, and other useful thermodynamic quantities directly from the charts. The accompanying text discusses the use of the data for various chemical calculations, while sources and accuracy of the data are discussed in the appendix.
153 citations
TL;DR: In this paper, the authors measured the A−(H2O)n−1−1 + H2O n−1+ H 2O n −1−H 2O = A−H n−n− 1 + H 2 O n− 1 −1 −H 2 O−n −1+H 2 N−1
Abstract: By measuring the A−(H2O)n−1 + H2O = A−(H2O)n equilibria in the gas phase and their temperature dependence, the equilibrium constants and ΔHn, n–1 and ΔSn, n–1 for some of the hydrates of NO2−, NO3−, CN−, and OH− were determined. Available thermochemical data are used for the evaluation of the total heats of hydration of the above ions. The total heats of hydration were then compared with the ΔH1,0. Relative to the total hydration energies the ΔH1,0 of the above ions were found larger than the ΔH1,0 of the halide ions.An approximate linear correlation was found to exist between ΔH1,0 of negative ions and the heterolytic bond dissociation energy D(A−–H+). With this relationship independent estimates for the electron affinities of NO2 and NO3 could be obtained.The ΔHn, n–1 of OH− were found in essential agreement with earlier measurements from this laboratory and in disagreements with recent measurements (Friedman) which gave much higher values.
116 citations
TL;DR: In this article, the equilibrium constant for the reaction between cupric and bicarbonate ions which results in the formation of the soluble complex species, CuCO3, was determined by means of a cupric ion selective electrode.
112 citations
TL;DR: In this paper, a study of point defects and non-stoichiometry in GaAs is presented, and the minimum practical deviation from stoichiometry and the width of the existence region of solid GaAs are calculated as a function of temperature.
110 citations
TL;DR: In oxyhemoglobin, dissociation into monomers was not sufficient to be detectable even at high salt concentrations, and the association-dissociation equilibrium conformed well to a simple dimer-tetramer equilibrium, explaining the “salt paradox”.
109 citations
TL;DR: Binding studies using equilibrium dialysis are shown to confirm earlier evidence, obtained by spectrophotometric titration, that yeast glyceraldehyde-3-phosphate dehydrogenase binds four molecules of nicotinamide-adenine dinucleotide in a co-operative manner at pH 8.5 and 40 °C.
97 citations
81 citations
TL;DR: In this paper, a pulse radiolysis technique was applied to pyrene in solutions of benzonitrile, acetone, and dichloroethane to investigate the decay of pyrene monomer and dimer cations.
Abstract: Radical cations of pyrene were investigated by the pulse radiolysis technique in solutions of benzonitrile, acetone, and dichloroethane. A 450‐nm absorption band of a pyrene monomer cation was replaced by new bands with maxima at 500, 580, and 750 nm as the pyrene concentration was increased. The latter absorption bands were exclusively assigned to a pyrene dimer cation in equilibrium with the monomer cation at room temperature. Equilibrium constants evaluated were (2.7 ± 0.2) × 102and (5.1 ± 0.5) × 102M−1 at 20°C for benzonitrile and acetone solutions, respectively. The decay processes of both the monomer and dimer cations were discussed. In addition, rate constants of the reactions of both the monomer and dimer cations with triethylamine were found to be 2.7 × 109and 5.4 × 108M−1·sec−1, respectively.
TL;DR: The formation of the guanosine-glyoxal adduct is slower than those of adenosine and cytidine, but the reaction product is much more stable and the stability of the adduct increases in borate buffers.
TL;DR: Under all the experimental conditions investigated the β chain association and dissociation rate constants were both significantly greater than the corresponding α chain constants, and the equilibrium constants for both chains were roughly equivalent.
TL;DR: Acid-base titrations were performed on oxygenated and deoxygenated erythrolysates at constant PCO2 and the equilibrium constants Kz (acid-base) and Kc (carbamate) of the terminal -NH2 of the β-chains of deoxy-hemoglobin were evaluated.
Abstract: Acid-base titrations were performed on oxygenated and deoxygenated erythrolysates at constant PCO2. The Haldane coefficient, - (δHb-bound H+)/(δHb-bound O2), was determined as a function of pH and PCO2 for various concentrations of 2,3-diphosphoglycerate (DPG). At PCO2=0 DPG causes a decrease or increase in the coefficient for pH 7.0, respectively. The equilibrium constants Kz (acid-base) and Kc (carbamate) of the terminal -NH2 of the β-chains of deoxy-hemoglobin were evaluated. DPG decreases both constants, especially Kz.
TL;DR: In this paper, afterglow techniques have been employed to determine reaction rate constants for ions reacting in NO-H2O gas mixtures, and rate constants and/or equilibrium constants are provided for all forward and all reverse reactions at 296°K.
Abstract: Stationary afterglow techniques have been employed to determine reaction rate constants for ions reacting in NO–H2O gas mixtures. Krypton resonance radiation at 123.6 and 116.5 nm is used to ionize only the NO molecules. The NO+ ion is the precursor to a chain of reactions which result in NO+·nNO(n = 1,2), NO+·nH2O(n = 1,2,3), and H3O+·nH2O(n = 2,3,4) being formed. Rate constants and/or equilibrium constants are provided for all forward and all reverse reactions at 296°K.
TL;DR: The spectral broadening and intensity measurements are consistent with the hypothesis that a myosin monomer‐dimer equilibrium exists in these solutions and are discussed in terms of the models of Huxley and Pepe for the structure of the myofilament.
Abstract: Homodyne and heterodyne measurements have been made of the spectrum and intensity of laser light scattered from solutions of skeletal muscle myosin at high salt concentrations. The spectral broadening and intensity measurements are consistent with the hypothesis that a myosin monomer-dimer equilibrium exists in these solutions. Values have been calculated for molecular weight and radius of gyration of the myosin monomer, virial coefficients, and diffusion constants of both monomer and dimer, and equilibrium constant of the reaction to form dimer. Diffusion constant measurements yield an approximate length of 1481 A for the monomer and 2121 A for the dimer. The significance of these lengths is discussed in terms of the models of Huxley and Pepe for the structure of the myofilament.
TL;DR: In this paper, the equilibrium constant for transfer of hydrogen atoms from the surface to the bulk of a palladium membrane was measured and the apparent standard free energy for the process increases linearly with fractional coverage up to θ = 0·15 and remains constant at higher values of θ, indicating the existence of two types of surface sites.
TL;DR: A consideration of the stabilities of the Fe2+ and Mg2+ chelates together with the occurrence of these metal ions in synaptosomes suggests their possible involvement in the intra vesicular amine‐binding and storage sites.
Abstract: — Equilibrium studies on the interaction of biogenic amines with iron (Fe2+ and Fe3+) and magnesium (Mg2+) were undertaken in an attempt to correlate the stabilities of metal-amine chelates and the reported granule-binding affinities of the biogenic amines. By means of potentiometric equilibrium measurements at 25°C and an ionic strength of 10 (KNO3) the formation constants of the Fe2+ chelates with norepinephrine (NE) and adenosine-S-triphosphate (ATP) were determined. Possible structures were derived for the co-ordinate binding of Fe2 + with NE. The interactions of Fe2+ and Fe2+-ATP with NE were investigated and the formation of Fe2+-NE-ATP (1:1:1) mixed ligand ternary chelate was proposed on the basis of the equilibrium data. Information obtained from chelation studies of Fe2+ with pyrocatechol and ethanolamine taken together with the data obtained on the Fe2+-NE system indicated that the binding of Fe2+ by NE was probably via the pyrocatechol moiety. Equilibrium constants for the binding of tyramine (TA) dopamine (DA) and NE with Mg2+ were also determined. The equilibrium data obtained on the Mg2+-amine systems indicated a correlation between the metal-amine binding affinities and the structure and amine-release (and storage) activities of the biogenic amines. A consideration of the stabilities of the Fe2+ and Mg2+ chelates together with the occurrence of these metal ions in synaptosomes suggests their possible involvement in the intra vesicular amine-binding and storage sites.
TL;DR: The bell-shaped pH-rate profiles cannot be explained completely by the ionization of reactants, but they can be interpreted by postulating the presence of an imine intermediate that undergoes attack by water or hydroxide to form a carbinolamine which subsequently decomposes to products.
TL;DR: The model accurately predicts the equilibrium behavior of this protein without considering aggregation above the level of the dimer, and Physiologically, higher aggregates may not have functional importance.
TL;DR: Results indicate that the role played by axial dispersion in small zone profiles is dramatically different from that in corresponding large zone (plateau) experiments, and the bimodal character of monomer-n-mer systems seen in derivative profiles from large zone experiments is greatly diminished and largely obscured.
TL;DR: In this article, the interaction of iron(III) and uranyl ions with dissolved silica is studied by a spectrophotometric technique, and the interaction with iron is studied as a function of the degree of polymerization of the silica.
TL;DR: In this article, the principal product ion is C2O2+ formed by a three-body process at pressures above 0.2 torr and small additions of CO, and the only reaction observed in the protonation of CO by CH5+ with a rate constant of 5.54 × 10−10 cm3 molecule−1·sec−1.
Abstract: In carbon monoxide at pressures above 0.2 torr, the principal product ion is C2O2+ formed by a three‐body process. The rate constant for the reaction is 1.43 × 10−28 cm6 molecule−2·sec−1. Above about 0.8 torr, the reaction appears to approach equilibrium with an equilibrium constant of 1482 referred to 1 atm as standard. At pressures of methane above 0.2 torr and small additions of CO, the only reaction observed in the protonation of CO by CH5+ with a rate constant of 5.54 × 10−10 cm3 molecule−1·sec−1. All other reactions are endothermic and are not observed. At pressures of carbon monoxide above 0.2 torr, the addition of small amounts of methane results in an H‐atom transfer reaction to CO+ with a rate constant of 13.7 × 10−10 cm3 molecule−1·sec−1. In addition, C2O2+ reacts to form HCO+, C2H3O+, and C3H3O+ with rate constants of 9.44, 4.37, and 0.76 × 10−10 cm3 molecule−1·sec−1, respectively.
TL;DR: With a partially purified enzyme from Brevibacterium liquefaciens, the adenylate cyclase reaction, ATP → cyclic AMP + PPi, was demonstrated to be readily reversible, indicating a high free energy of hydrolysis for the 3' ester bond of cyclic adenosine 3',5'-monophosphate (cyclicAMP).
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TL;DR: In this paper, the rate of absorption and chemical reaction of carbon dioxide in potassium carbonate-bicarbonate buffer solutions was measured, at 80°C. The absorption rates measured were correlated with penetration and surface renewal theory.
TL;DR: The effective Bohr magneton numbers (neff) of the enzyme at different pH values were explained by assuming that cytochrome c peroxidase is a mixture of acidic and alkaline forms and that both forms have low spin and high spin states in thermal equilibria.
TL;DR: The oxidation states of the primary and secondary electron acceptors of Photosystem II in isolated chloroplasts were measured simultaneously during their oxidation and reduction and influence of the light, by secondary interactions, on reaction parameters was discussed.
TL;DR: Kinetic models for haemoglobin based on the perfect equivalence of function of the two chains will require reconsideration in the case of some ligands, which may indicate steric effects.
TL;DR: It is proposed for both solutions to use the same coefficient pK1g of the modified Henderson-Hasselbalch equation: pH = pK*1g + log [HCO3−]t−logPco2 in the range of temperature 25°–38° and pH 6.8–7.8, using the Radiometer micro glass electrode cell for pH measurement.
TL;DR: In this paper, a rate constant for O2(1Δg)+O3→2O2+O of 4.5×10−11exp(− 5620 /
Abstract: A rate constant for the reaction O2(1Δg)+O3→2O2+O of 4.5 × 10−11exp(− 5620 / RT)cm3molecule−1·sec−1 over the temperature range 283–321°K has been obtained. The rate of the reverse reaction, calculated from the equilibrium constant, is 8.7 × 10−37exp(− 3340 / RT)cm6molecule−2·sec−1.