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Experiments, equilibrium

Electrochemical methods may be classified into two broad classes, namely potentiometric metiiods and voltannnetric methods. The fonner involves the measurement of the potential of a working electrode iimnersed in a solution containing a redox species of interest with respect to a reference electrode. These are equilibrium experiments involving no current flow and provide themiodynamic infomiation only. The potential of the working electrode responds in a Nemstian maimer to the activity of the redox species, whilst that of the reference electrode remains constant. In contrast, m voltannnetric methods the system is perturbed... [Pg.1921]

Apart from tliese mainstream metliods enabling one to gain a comprehensive and detailed stmctural picture of proteins, which may or may not be in tlieir native state, tliere is a wide variety of otlier metliods capable of yielding detailed infonnation on one particular stmctural aspect, or comprehensive but lower resolution infonnation while keeping tlie protein in its native environment. One of tlie earliest of such metliods, which has recently undergone a notable renaissance, is analytical ultracentrifugation [24], which can yield infonnation on molecular mass and hence subunit composition and their association/dissociation equilibria (via sedimentation equilibrium experiments), and on molecular shape (via sedimentation velocity experiments), albeit only at solution concentrations of at least a few tentlis of a gram per litre. [Pg.2818]

Le Chatelier s Principle permits the chemist to make qualitative predictions about the equilibrium state. Despite the usefulness of such predictions, they represent far less than we wish to know. It is a help to know that raising the pressure will favor production of NH3 in reaction (10a). But how much will the pressure change favor NH3 production Will the yield change by a factor of ten or by one-tenth of a percent To control a reaction, we need quantitative information about equilibrium. Experiments show that quantitative predictions are possible and they can be explained in terms of our view of equilibrium on the molecular level. [Pg.151]

Barrett and Thomas (10)proposed that these effects of differential monomer adsorption could be modeled by correcting homogeneous solution copolymerization reactivity ratios with the monomer s partition coefficient between the particles and the diluent. The partition coefficient is measured by static equilibrium experiments. Barrett s suggested equations are ... [Pg.274]

The centrifugal field in the sedimentation equilibrium experiment is the analog of the membrane in an osmometer. [Pg.307]

Duever, T.A., S. E. Keeler, P.M. Reilly, J.H. Vera, and P.A. Williams, "An Application of the Error-In-Variables Model-Parameter Estimation from van Ness-type Vapour-Liqud Equilibrium Experiments", Chem. Eng Sci., 42, 403-412 (1987). [Pg.393]

Sutton, T.L., and J.F. MacGregor, "The Analysis and Design of Binary Vapour-Liquid Equilibrium Experiments Part I Parameter Estimation and Consistency Tests", Can. J. Chem. Eng., 55, 602-608 (1977). [Pg.401]

GC, utilizing flame ionization detection (FID), has been used to measure diisopropyl methylphosphonate in meat, grain, or milk (Caton et al. 1994). Sample preparation steps include homogenization, filtration, dialysis, and extraction on a solid sorbent. Two common solid phase extractants, Tenax GC and octadecylsilane bonded silica gel (C18 Silica), were compared by Caton et al. (1994). They reported 70% recovery when using Tenax GC and 85% recovery when using C18 Silica. Sensitivity was not reported. Equilibrium experiments indicate that 8-10 mg of Tenax GC are required to achieve maximum recovery of each g of diisopropyl methylphosphonate (Caton et al. 1994). By extrapolating these... [Pg.130]

Solutions of aluminium bromide in dichloromethane used as a catalyst in hydride-transfer equilibrium experiments should be kept cold, as a potentially dangerous exothermic halide exchange reaction occurs on warming. [Pg.42]

The source of some of the difficulties encountered in trying to explain the effects of structural changes on ionization rates may be due to the different parts played by the solvent, as for example, the sulfur dioxide of the trityl chloride equilibrium experiments and the aqueous acetone of the benzhydryl chloride rate data. The solvent is bound to modify the effect of a substituent, and although the solvent is usually ignored in discussing substituent effects this is because of a scarcity of usable data and not because the importance of the solvent is not realized "... solvation energy and entropy are the most characteristic determinants of reactions in solution, and... for this class of reactions no norm exists which does not take primary account of solvation. 220 Precisely how best to take account of solvation is an unanswered problem that is the subject of much current research. [Pg.112]

Alternatively, in sedimentation equilibrium experiments, the ultracentrifuge is operated at slow speeds for longer time to permit the solute molecules to attain equilibrium between sedimentation and diffusion. If the sample is monodisperse, its concentrations cb c2 can be measured at 2 positions xh x2 in the cell. [Pg.124]

The second reaction studied using lipase as catalyst was the reversible re-gioselective esterification of propionic acid and 2-ethyl- 1,3-hexanediol [180]. While the previously described reaction was almost irreversible, this reaction is equilibrium limited with an apparent equilibrium constant of 0.6 0.1. In addition, the accumulated water inhibits the enzyme. Therefore, only the removal of the water from the reaction zone assures high enzymatic activity as well as drives the reaction beyond thermodynamic equilibrium. Experiments with two... [Pg.202]

Equilibrium experiments such as 10, 11, and 19 in Chapter 19, directly or indirectly involve filling a table like the following ... [Pg.230]

The NaHSOg was analyzed by iodine titration and was typically 97-98% of the expected SO2 content. Several of the solutions used for vapor/liquid equilibrium experiments were analyzed for total SO2 and found to contain 5 to 10% less than the nominal concentration. Nominal concentrations were used in presenting and analyzing the data, unless noted otherwise. Therefore, correlated values of Pgc may he 5 to 10% low for a given solution composition. [Pg.270]

Measurements of dissolved sorbing phase (e.g., weight of dissolved solids, turbidity, and DOC) demonstrate the increased loading of nonsettling microparticles or macromolecules in the supernatants of batch equilibrium experiments as the solids-to-water ratio increases. It is clear that nonsettling microparticles or macromolecules vary regularly with suspended solid concentration. [Pg.127]

The prefix poten- is generally used for measurements of potential determined at zero current, so the potential is essentially constant, i.e. measured in an equilibrium experiment. [Pg.8]

A lack of agreement between the Kj estimated in equilibrium experiments and that determined in kinetic experiments (k i/ki = Kd) suggests a more complex ligand-receptor interaction. [Pg.265]

In Fig. 3.16 dynamic structure factor data from a A =36 kg/mol PE melt are displayed as a function of the Rouse variable VWt (Eq. 3.25) [4]. In Fig. 3.6 the scaled data followed a common master curve but here they spht into different branches which come close together only at small values of the scahng variable. This splitting is a consequence of the existing dynamic length scale, which invalidates the Rouse scaling properties. We note that this length is of purely dynamic character and cannot be observed in static equilibrium experiments. [Pg.48]

The yttrium monocarbide molecule was only recently observed under high resolution by Simard et al. (37) using Jet-cooled optical spectroscopy. The ground electronic state was determined to be an 0=5/2 state, which was consistent with the ab initio calculations of Shim et al. (38) who predicted a 11 ground state for YC in CASSCF calculations. The experimental work of Simard et al. yielded estimates for both the bond length and harmonic frequency of YC. In addition to their CASSCF calculations. Shim et al. (38) also reported results from mass spectrometric equilibrium experiments, which resulted in a bond dissociation energy of Do = 99.0 3.3 kcal/mol. The results from the present work are shown in Table I. An open-shell coupled cluster singles and doubles... [Pg.140]

Chemical equilibrium experiments, e.g., distribution ratio measurements, cannot distinguish between these two types of complexes however, they may be identified by fingerprinting techniques like NMR, IR, or x-ray structure determinations. Existence of similar adducts like MA Bb support the existence of self-adducts. The case of promethium(lll) acetylacetone is an interesting illustration of this problem. [Pg.159]

Koziol A. M. (1990). Activity-composition relationship of binary Ca-Fe and Ca-Mn garnets determined by reversed, displaced equilibrium experiments. Amer. Mineral, 75 319-327. [Pg.840]

A potential limitation encountered when one seeks to characterize the kinetic binding order of certain rapid equilibrium enzyme-catalyzed reactions containing specific abortive complexes. Frieden pointed out that initial rate kinetics alone were limited in the ability to distinguish a rapid equilibrium random Bi Bi mechanism from a rapid equilibrium ordered Bi Bi mechanism if the ordered mechanism could also form the EB and EP abortive complexes. Isotope exchange at equilibrium experiments would also be ineffective. However, such a dilemma would be a problem only for those rapid equilibrium enzymes having fccat values less than 30-50 sec h For those rapid equilibrium systems in which kcat is small, Frieden s dilemma necessitates the use of procedures other than standard initial rate kinetics. [Pg.298]

SEC-MALLS and SEC-LALLS Coupled chromatography and light-scattering photometry that allows the determination of a number of important values along with chain length distribution, sedimentation equilibrium experiment Ultracentrifugation technique that allows chain length information to be determined. [Pg.80]

The concept of transport resistances localized in the outermost regions of NS crystals was introduced in order to explain the differences between intracrystalline self-diffusion coefficients obtained by n.m.r methods and diffusion coefficients derived from non-equilibrium experiments based on the assumption that Intracrystalline transport is rate-limiting. This concept has been discussed during the past decade, cf. the pioneering work [79-81] and the reviews [2,7,8,23,32,82]. Nowadays, one can state that surface barriers do not occur necessarily in sorption uptake by NS crystals, but they may occur if the cross-sections of the sorbing molecular species and the micropore openings become comparable. For indication of their significance, careful analysis of... [Pg.205]

Kinetic experiments, while useful in estimating the adatom cohesive energy of a cluster, become very complicated if pair energies at more than one bond state, or information on the inter-adatom potential, are desirable. The distance dependence of pair interaction can be more easily derived by an equilibrium experiment.173 The principle is very simple. At equilibrium, the relative frequencies of observing the two adatoms at various bond states or bond separations at a given temperature are related to their pair energies according to the Boltzmann factors. Thus... [Pg.247]

Vapor-liquid equilibrium experiments were performed with an improved Othmer recirculation still as modified by Johnson and Furter (2). Temperatures were measured with Fisher thermometers calibrated against boiling points of known solutions. Equilibrium compositions were determined with a vapor fractometer using a type W column and a thermal conductivity detector. The liquid samples were distilled to remove the salt before analysis with the gas chromatograph the amount of salt present was calculated from the molality and the amount of solvent 2 present. Temperature measurements were accurate to 0.2°C while compositions were found to be accurate to 1% over most of the composition range. The system pressure was maintained at 1 atm. 1 mm... [Pg.46]

Equilibrium experiments are carried out under zero-current conditions. Yielding no kinetic information, such experiments need not detain us. [Pg.102]


See other pages where Experiments, equilibrium is mentioned: [Pg.640]    [Pg.229]    [Pg.13]    [Pg.35]    [Pg.523]    [Pg.387]    [Pg.200]    [Pg.84]    [Pg.38]    [Pg.125]    [Pg.7]    [Pg.209]    [Pg.219]    [Pg.16]    [Pg.17]    [Pg.105]    [Pg.271]    [Pg.16]    [Pg.602]    [Pg.227]    [Pg.331]    [Pg.257]    [Pg.101]   
See also in sourсe #XX -- [ Pg.137 ]

See also in sourсe #XX -- [ Pg.5 ]




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Apparent transfer parameters relevant to the static equilibrium experiment and gel chromatography

Conventional sedimentation equilibrium experiments

Electrochemical Experiments in Systems Far from Equilibrium

Equilibria laboratory experiments

Equilibrium exchange experiments

Equilibrium experiment, sedimentation

Equilibrium experiments and their interpretation

Equilibrium industrial experience

Equilibrium partitioning experiments

Experiment 10 B Determination of the Equilibrium Constant, KsP, for a Chemical Reaction

Experiment 10 Finding the Equilibrium Constant

Experiments on Chemical Equilibrium

Model Experiment on Dynamic Equilibrium

Phase equilibrium experiments

Pilot plant equilibrium experiments

Sorption equilibrium experiments

Transfer equilibrium experiments

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