The osmotic second virial coefficient and the Gibbs–McMillan–Mayer framework

The osmotic second virial coefficient is a key parameter in light scattering, protein crystallisation, self-interaction chromatography, and osmometry. The interpretation of the osmotic second virial coefficient depends on the set of independent variables. This commonly includes the independent variables associated with the Kirkwood–Buff, the McMillan–Mayer, and the Lewis–Randall solution theories. In this paper we analyse the osmotic second virial coefficient using a Gibbs–McMillan–Mayer framework which is similar to the McMillan–Mayer framework with the exception that pressure rather than volume is an independent variable. A Taylor expansion is applied to the osmotic pressure of a solution where one of the solutes is a small molecule, a salt for instance, that equilibrates between the two phases. Other solutes are retained. Solvents are small molecules that equilibrate between the two phases. The independent variables of the solvents are temperature, pressure, and chemical potentials. The derivatives in the Gibbs–McMillan–Mayer framework are transformed into derivatives in the Gibbs framework. This offers the possibility for an interpretation and correlation of the osmotic second virial coefficient using activity coefficient models.     

Chemical Laws and Theories: A Response to Vihalemm

A recent article by Vihalemm (Foundations of Chemistry, 2003) is critical of an earlier essay. We find that there is some justification for his criticism of vagueness in defining terms. Nevertheless the main conclusions of the earlier work, when carefully restated to deflect Vihalemm’s criticisms, are unaffected by his arguments. The various dicta that are used as the bases of chemical explanations are different in character, and are used in a different way from the laws and theories in classical physics. This revised version was published online in July 2006 with corrections to the Cover Date.     

Equivalent Potential Functions to Calculate Thermodynamic Equilibria*

The present paper contains an analysis of alternative functions to describe chemical equilibrium. In particular we show the equivalence of equilibrium criteria based on pressure, volume and temperature, and corresponding constraints, with respect to those popularly used in thermodynamics, i.e. those based on the minimization of internal energy, enthalpy, Helmholtz and Gibbs potentials. The analysis emphasizes the role of mathematical virtual procedures in determining the equilibrium conditions and the irrelevance of physico-chemical transformations that bring the system into the equilibrium state. Different examples, including a new derivation of Saha’s equation, are dealt with to validate this conceptual approach. This paper is dedicated to the memory of one of the authors, Giuseppe Petrella, who unfortunately is not with us any more.     

Accurate and local formulation for thermodynamic properties directly from integral equation method

A local formulation for determination of excess chemical potential is derived out by applying an assumption of linear dependence of correlation function and bridge function on the charging parameter to the Kirkwood charging formula and scaling the bridge function, the scaling parameter is specified by a Gibbs–Duhem relation. The local formulation for the excess chemical potential only requires the correlation function and bridge function of the investigated state as input and is therefore free of an unwieldy thermodynamic integration. A comprehensive comparison between the presently calculated thermodynamic quantities for a Lennard–Jones (LJ) fluid including two key quantities, i.e. the excess chemical potential and excess entropy, corresponding simulation data available in literature, and corresponding calculated results by several other global and local formulations, indicates that the present formulation is the only one capable of predicting locally and excellently all of the thermodynamic properties of the LJ fluid. The GCMC simulation is carried out for a core-softened potential fluid and the LJ fluid near critical state and at subcritical state near the gas–liquid coexistence line to obtain the excess chemical potential which is also in excellent agreement with the theoretical prediction from the present formalism; this indicates that the present formalism is of general interest in fluid statistical mechanics and applicable to parameter space covering over the entire phase diagram.     

Model hysteresis dimer molecule II: deductions from probability profile due to system coordinates

The hysteresis dimer reaction of the first sequel is applied to test the Gibbs density-in-phase hypothesis for a canonical distribution at equilibrium. The probability distribution of variously defined internal and external variables is probed using the algorithms described, in particular the novel probing of the energy states of a labeled particle where it is found that there is compliance with the Gibbs’ hypothesis for the stated equilibrium condition and where the probability data strongly suggests that an extended equipartition principle may be formulated for some specific molecular coordinates, whose equipartition temperature does not equal the mean system temperature and a conjecture concerning which coordinates may be suitable is provided. Evidence of violations to the mesoscopic nonequilibrium thermodynamics (MNET) assumptions used without clear qualifications for a canonical distribution for internal variables are described, and possible reasons outlined, where it is found that the free dimer and atom particle kinetic energy distributions agree fully with Maxwell–Boltzmann statistics but the distribution for the relative kinetic energy of bonded atoms does not. The principle of local equilibrium (PLE) commonly used in nonequilibrium theories to model irreversible systems is investigated through NEMD simulation at extreme conditions of bond formation and breakup at the reservoir ends in the presence of a temperature gradient, where for this study a simple and novel difference equation algorithm to test the divergence theorem for mass conservation is utilized, where mass is found to be conserved from the algorithm in the presence of flux currents, in contradiction to at least one aspect of PLE in the linear domain. It is concluded therefore that this principle can be a good approximation at best, corroborating previous purely theoretical results derived from the generalized Clausius Inequality, which proved that the PLE cannot be an exact principle for nonequilibrium systems.      

Complementarity and the temporal Uncertainty principle. Insight into the dichotomous formulations of the Curtin-Hammett principle. A new formulation

By the temporal Uncertainty principle, chemical systems may be described in terms of ‘kinetic’ or ‘thermodynamic’ complementary formulations, based on rate or equilibrium constants, and free energy changes respectively. Thereby, the paradox of the dichotomous formulations of the Curtin-Hammett principle is resolved. A new formulation of the principle is suggested, and a fundamental conflict with transition state theory is indicated.     

Chemical speciation code CHEMSPEC and its applications

The adsorption and migration behavior of a radionuclide in geological media heavily depends on its chemical forms in a given chemical environment. In order to predict the temporal and spatial distribution of radionuclides around a disposal site when its canister is damaged, it is necessary to develop coupled chemical speciation-solute transport models and relevant software. For that reason, we wrote a new chemical speciation program CHEMSPEC. In this paper, the principles and structure of CHEMSPEC are briefly described, and the strategy and algorithms that were used in this code are interpreted in some detail, such as the measures adopted to prevent divergence in iteratively solving the mass balance equations, the “predictor-corrector” algorithm for calculation of the number and quantities of solid species formed, and the alternate use of “freezing” and “defreezing” oxidation states in handling of co-existent redox and precipitation equilibria. Four examples are given to illustrate CHEMSPEC’s features and capabilities.     

Effective potential, Bohm’s potential plus classical potential, analysis of quantum transmission

The influence of spreading, in wavepacket transmission across a potential barrier has been analyzed, by considering several collisions between a wavepacket and a potential barrier, in which the initial distance between the packet and the barrier—the launching distance, is changed. An effective total potential (Bohm’s quantum potential plus classical potential), has been used, to show that, for suitable classical barrier widths and heights, light masses, as well as mean collision energies, one should expect an increase of the quantum transmission factor as the initial wavepacket—barrier distance is decreased. Numerically converged time-dependent wavepacket propagation calculations confirm that trend, leading to an increase as high as 20% per ?, in thin square and Eckart barrier problems. Possibilities of experimentally measuring this effect are also analyzed.     

The Structure of Chemical Particles

The possibility of predicting on a purely theoretical basis the existence of some “elementary” particles composing chemical particles (atoms, molecules) is studied. For this purpose the notion of Fock theories in separable Hilbert spaces is introduced. By using the mathematical structure of Fock theory—which is a nontrivial generalization of the Fock space—the notion of particle as sharp entity is defined. It is proved that chemical changes cannot be described by those Fock theories, which consider particles as sharply defined entities. This is a consequence of quantum-mechanical dynamical postulate concerning time evolutions of conservative systems. Finally it is shown that a category of Fock theories may describe changes in the number of chemical particles during conservative evolutions. This result is naturally obtained if the hypothesis about existence of some “elementary particles” composing chemical particles is accepted. Another simultaneously obtained conclusion is that chemical particles involved in chemical processes cannot be sharply defined.     

Entropy Structure Within a Cosserat Fluid Involving Chemical Reactions,Heat, and Mass Transfer

In this contribution, the entropy balance equation of a Cosserat-type fluid involving chemical reactions, heat and mass transfer is derived from Gibbs relation. To this aim, the balance equations of internal, kinetic, potential and total energies of a Cosserat-type fluid are derived. Some new terms appear in the aforementioned equations in comparison to the classical theory. In the case of kinetic energy, a new balance equation is derived from the conservation law of angular momentum. The obtained equations give a deep insight into the energy content and structure of entropy within such a continuum as well as the mechanisms of energy dissipation.     

Is there a quantum definition of a molecule?

The paper surveys how chemistry has developed over the past two centuries starting from Lavoisier’s classification of the chemical elements at the end of the eighteenth century; the subsequent development of the atomic–molecular model of matter preoccupied chemists throughout the nineteenth century, while the results of the application of quantum theory to the molecular model has been the story of this century. Whereas physical chemistry originated in the nineteenth century with the measurement of the physical properties of groups of chemical compounds that chemists identified as families, the goal of chemical physics is the explanation of the facts of chemistry in terms of the principles and theories of physics. Chemical physics as such was only possible after the discovery of the quantum theory in the 1920’s. By then the first of the sub‐atomic particles had been discovered and seemingly it is no longer possible to discuss chemical facts purely in terms of atoms and molecules – one has to recognize the electron and the nucleus, the parts of atoms. The combination of classical molecular structure with the quantum properties of the electron has given us a tremendously successful account of chemistry called ‘quantum chemistry’. Yet from the perspective of the quantum theory the deepest part of chemistry, the existence of chemical isomers and the very idea of molecular structure that rationalizes it, remains a central problem for chemical physics. This revised version was published online in July 2006 with corrections to the Cover Date.     

细胞粘附位点RGD前体二肽的化学合成与酯化

摘要利用一种新颖的化学法合成了细胞粘附位点RGD前体二肽GD(Gly-Asp). 并利用ROH-HCl法进一步完成了GD二肽乙酯化和甲酯化. 考察了GD二肽对乙醇/甲醇的摩尔比,  反应温度和反应时间对酯化收率的影响, 使GD二肽酯化的条件得到了优化, GD二肽对乙醇/甲醇的摩尔比为1∶40,  反应温度30℃,  反应时间1~2.5 h,   最大收率为80%~85%. 利用质谱分析法确证了两种GD二肽酯为Gly-Asp-(OEt)2 和Gly-Asp-(OMe)2.     

Photopolymerized silver-containing conducting polymer films. Part I. An electronic conductivity and cyclic voltammetric investigation

A photopolymerization process that simultaneously deposits electronically conducting polymer films and incorporates nanophase silver grains within the films, the silver grains having been formed in situ on irradiating cast, photopolymerizable formulations containing silver salts, was developed. Polymer films produced from formulations containing large organic anions were very flexible and strongly adherent to substrates. Polypyrrole films containing silver grains were characterized electronically on measuring their electronic conductivities and electrochemically on recording their cyclic voltammetric profiles. Conductivities were affected by the chemical identity and concentration of components added to photopolymerizable formulations. The best photopolymerized films had a conductivity of the order of 1 S cm⁻¹. Electronically conducting films derived from formulations consisting of a monomer, an electron acceptor/“dopant,” and a photoinitiator were electrochemically active. They possessed long-term stability under extended electrode potential cycling conditions, acceptable charge storage capacity, and the ability to oxidize or reduce redox couples in solution. Paper submitted for inclusion in the special issue of the Journal of Solid State Electrochemistry honouring the 85th birthday of Professor John O’M. Bockris.     

The development of the fundamental concepts of surface thermodynamics

Author’s results concerning the most fundamental problems of the thermodynamics of surface phenomena are reviewed. The generalized Laplace-Young-Kelvin equation, phase rules, and Gibbs adsorption equations are presented. Analogs of Konovalov’s laws are describes as applied to surface phenomena. The surface tension dualism, the Gibbs equation for adsorption on solid surfaces, and the phase equilibrium condition for a soluble nanoparticle are explained. The general mechanochemical approach, chemical affinity tensor, and the discovery of the mechanochemical dissolution effect are characterized. A novel approach to the monolayer state equation is formulated based on an excluded area. The problems of nucleation and the theory of surface separation are reperted.     

Molecular Thermodynamics for Chemical Process Design

Thermodynamic properties are essential for quantitative process design to produce chemical products. Caloric properties are required for heat balances, but these properties are usually available or estimated easily. More important—and often much more difficult to estimate—are the chemical potentials of components in mixtures; it is these potentials which determine phase equilibria, as required for separation operations, and chemical equilibria, as required for chemical reactors and for separation operations based on chemical reactions. Molecular thermodynamics is an engineering-oriented science for calculating the desired chemical potentials from a minimum of experimental data. This applied science, based on classical and statistical thermodynamics, yields chemical potentials through models that are based on molecular physics and physical chemistry. Selected examples are cited to illustrate the applicability of molecular thermodynamics: group-contribution methods for obtaining chemical potentials in highly nonideal mixtures as required for distillation-column and process-safety design; equation of state for precipitation of uniform-sized crystals from supercritical fluids; molecular-orbital calculations to guide process development for alternatives to environmentally dangerous chlorofluorohydrocarbons; molecular-simulation calculations for separation of gas mixtures with porous adsorbents; equilibria in two-phase aqueous systems for separation of protein mixtures; and, finally, extended polymer-solution thermodynamics to guide synthesis of hydrogels suitable for protein recovery from soybeans and for novel drug-delivery devices.     

Linear Variational Diophantine Techniques in Mass Balance of Chemical Reactions

Linear algebraic techniques based on minimization of thermodynamic functional and/or other constraints are illustrated for mass balance of chemical reactions that do not exhibit stoichiometrically unique solutions in the linear algebraic vector space. The techniques demonstrate elegant casting of chemical equations in terms of generalized linear Diophantine matrices and generalized elimination and variational schemes.     

Chemical metrology in New Zealand

Recent developments in international trade will have a significant impact on New Zealand’s measurement infrastructure, especially for chemical metrology. This article describes the background to these developments and outlines the activities of the Measurement Standards Laboratory, New Zealand’s National Metrology Institute, in response to these developments.