Activities, thermodynamic

Copper is toxic in patients with Wilson s disease because its. thermodynamic activity is appreciable. In normal individuals the activity of copper is virtually zero because copper is almost always present only as the prosthetic element of one of another specific protein. A copper ion that is firmly bound to a specific copper-protein is not toxic, as exemplified by ceruloplasmin-copper, which is normally present at a concentration of about 100 micrograms per 100 ml. In the third trimester of pregnancy the plasma concentration of ceruloplasmin-copper normally and Innoc-ously rises as high as 300 micrograms per 100 ml. Yet 30 micrograms of non-ceruloplasmin-copper is a characteristic and highly toxic level in an untreated patient with Wilson s disease. 

It is paradoxical that in Wilson s disease it seems likely that free copper ions effect their toxicity by combining with sulfhydryl, carboxyl or amino groups of non-copper proteins and impairing their physiological roles. 

ACS Symposium Series American Chemical Society Washington, DC, 1980. 

Wilson s disease significantly increased the urinary excretion of copper(12). 

Although the rarity of Wilson s disease made it commercially unprofitable, it proved possible to induce a pharmaceutical company to manufacture D-penicillamine. In 1963 the United States Food and Drug Administration approved penicillamine as safe and effective in the treatment of Wilson s disease. 

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Osmotic pressure is one of four closely related properties of solutions that are collectively known as colligative properties. In all four, a difference in the behavior of the solution and the pure solvent is related to the thermodynamic activity of the solvent in the solution. In ideal solutions the activity equals the mole fraction, and the mole fractions of the solvent (subscript 1) and the solute (subscript 2) add up to unity in two-component systems. Therefore the colligative properties can easily be related to the mole fraction of the solute in an ideal solution. The following review of the other three colligative properties indicates the similarity which underlies the analysis of all the colligative properties ... 

The relationship of the vapour pressure of an element p, over a binary alloy, to the vapour pressure of the pure species p as determined by the thermodynamic activity, a, of the component in the alloy... 

NaCl, interact with the sulphur and vanadium oxides emitted from the combustion of technical grade hydrocarbons and die salt spray to form Na2S04 and NaV03- These conosive agents function in two modes, either the acidic mode in which for example, the sulphate has a high SO3 thermodynamic activity, of in the basic mode when the SO3 partial pressure is low in the combustion products. The mechanism of coiTosion is similar to the hot coiTosion of materials by gases widr the added effects due to the penetration of tire oxide coating by tire molten salt. 

A useful diagnostic tool for investigating possible hydration of cations of bases for which pA is greater than about one is the measurement of their ultraviolet spectra in aqueous acid solutions and also in an anhydrous acidic solvent such as dichloroacetic acid (for which the Hammett acidity function, Hq, is — 0.9, and in which hydration of the cation cannot occur). This technique has been used with quinazoline to obtain spectra approximating those of the hydrated and anhydrous cations, respectively. For weaker bases, spectral measurements in sulfuric acid-water mixtures of increasing acid content may be used to reveal a progressive conversion of hydrated into anhydrous species as the thermodynamic activity of the water decreases. 

By adding a third element (C) it is possible to increase the likelihood of forming compound BO, at a lower concentration than would be required in the pure binary alloy /4-B, provided that the third element C has an affinity for O intermediate between that of A and B" . If the mobility of B in the ternary alloy is high enough and element C has sufficient thermodynamic activity in the alloy to form CO, then the potential of O may be lowered to such an extent that BO forms more readily, i.e. element C acts as a getter for element B. Such behaviour is characteristic of, for instance, Fe-Al-Si and Fe-Cr-Si alloys. 

This high thermodynamic activity shows that gold is extremely unstable in an oxygenated cyanide solution. 

Trustworthy thermodynamic data for metal solutions have been very scarce until recently,25 and even now they are accumulating only slowly because of the severe experimental difficulties associated with their measurement. Thermodynamic activities of the component of a metallic solution may be measured by high-temperature galvanic cells,44 by the measurement of the vapor pressure of the individual components, or by equilibration of the metal system with a mixture of gases able to interact with one of the components in the metal.26 Usually, the activity of only one of the components in a binary metallic solution can be directly measured the activity of the other is calculated via the Gibbs-Duhem equation if the activity of the first has been measured over a sufficiently extensive range of composition. 

Rate constants and thermodynamic activation parameters. The rate constant for the reaction between C2H4 and HCN catalyzed by a nickel(0) complex was studied over a range of -50 to -10 °C in toluene.31 These authors give the activation parameters A//1 = 36.7kJmor andAS = -145 J mol-1 K I when the reaction rate was expressed using concentrations in the units molL-1 and time in the unit seconds. 

The thermodynamic activity equilibrium constant (Ka) is expressed in terms of mole fraction (X) and activity coefficient (y) by the following equation ... 

Wagner was first to propose the use of solid electrolytes to measure in situ the thermodynamic activity of oxygen on metal catalysts.17 This led to the technique of solid electrolyte potentiometry.18 Huggins, Mason and Giir were the first to use solid electrolyte cells to carry out electrocatalytic reactions such as NO decomposition.19,20 The use of solid electrolyte cells for chemical cogeneration , that is, for the simultaneous production of electrical power and industrial chemicals, was first demonstrated in 1980.21 The first non-Faradaic enhancement in heterogeneous catalysis was reported in 1981 for the case of ethylene epoxidation on Ag electrodes,2 3 but it was only... 

Wagner first proposed the use of such galvanic cells in heterogeneous catalysis, to measure in situ the thermodynamic activity of oxygen O(a) adsorbed on metal electrodes during catalytic reactions.21 This led to the technique of solid electrolyte potentiometry (SEP).22 26... 

The changeover to thermodynamic activities is equivalent to a change of variables in mathematical equations. The relation between parameters and a. is unambiguous only when a definite value has been selected for the constant p. For solutes this constant is selected so that in highly dilute solutions where the system p approaches an ideal state, the activity will coincide with the concenttation (lim... 

A possible reason for the departures from Pick s first law is the fact that the diffusion process tends to level chemical potentials (thermodynamic activities) rather than concentrations of the substances involved. Hence, the equation sometimes is written as... 

The intercalation compounds of lithium with graphite are very different in their behavior from intercalation compounds with oxides or halcogenides. Intercalation processes in the former compounds occur in the potential region from 0 to 0.4 V vs. the potential of the lithium electrode. Thus, the thermodynamic activity of lithium in these compounds is close to that for metallic lithium. For this reason, lithium intercalation compounds of graphite can be used as negative electrodes in batteries rather than the difficultly of handling metallic lithium, which is difficult to handle. 

The beginning of the twentieth century also marked a continuation of studies of the structure and properties of electrolyte solution and of the electrode-electrolyte interface. In 1907, Gilbert Newton Lewis (1875-1946) introduced the notion of thermodynamic activity, which proved to be extremally valuable for the description of properties of solutions of strong electrolytes. In 1923, Peter Debye (1884-1966 Nobel prize, 1936) and Erich Hiickel (1896-1981) developed their theory of strong electrolyte solutions, which for the first time allowed calculation of a hitherto purely empiric parameter—the mean activity coefficients of ions in solutions. 

Maximal reaction rate relative to the rate at thermodynamic activity of the substrate = 1. Initial rate (/xM/min). 

Considering only the aqueous phase of the biocatalytic system, the equilibrium constant for the reaction is given as a function of thermodynamic activities of the components shown ... 

Of special interest in liquid dispersions are the surface-active agents that tend to accumulate at air/ liquid, liquid/liquid, and/or solid/liquid interfaces. Surfactants can arrange themselves to form a coherent film surrounding the dispersed droplets (in emulsions) or suspended particles (in suspensions). This process is an oriented physical adsorption. Adsorption at the interface tends to increase with increasing thermodynamic activity of the surfactant in solution until a complete monolayer is formed at the interface or until the active sites are saturated with surfactant molecules. Also, a multilayer of adsorbed surfactant molecules may occur, resulting in more complex adsorption isotherms. 

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