scholarly journals Predictive models for the phase behaviour and solution properties of weak electrolytes: nitric, sulphuric, and carbonic acids

2020 ◽  
Vol 22 (27) ◽  
pp. 15248-15269 ◽  
Author(s):  
Maximilian Kohns ◽  
Georgia Lazarou ◽  
Spiros Kournopoulos ◽  
Esther Forte ◽  
Felipe A. Perdomo ◽  
...  
Keyword(s):  
Predictive Models ◽  
Ion Pairing ◽  
Phase Behaviour ◽  
Solution Properties ◽  
Weak Electrolyte ◽  
Weak Electrolytes ◽  
Carbonic Acids

SAFT-VRE Mie allows for elucidating association and ion pairing in weak electrolyte systems.

scholarly journals Predictive models for the phase behaviour and solution properties of weak electrolytes: nitric, sulphuric, and carbonic acids

2021 ◽  
Author(s):  
Maximilian Kohns ◽  
Georgia Lazarou ◽  
Spiros Kournopoulos ◽  
Esther Forte ◽  
Felipe A. Perdomo ◽  
...  
Keyword(s):  
Equilibrium Constants ◽  
Ion Pairing ◽  
Ionic Species ◽  
Phase Behaviour ◽  
Solution Properties ◽  
Science And Engineering ◽  
Degree Of Dissociation ◽  
Hydronium Ion ◽  
Weak Electrolytes ◽  
Carbonic Acids

The distribution of ionic species in electrolyte systems is important in many fields of science and engineering, ranging from the study of degradation mechanisms to the design of systems for electrochemical energy storage. Often, other phenomena closely related to ionic speciation, such as ion pairing, clustering and hydrogen bonding, which are difficult to investigate experimentally, are also of interest. Here, we develop an accurate molecular approach, accounting for reactions as well as association and ion pairing, to deliver a predictive framework that helps validate experiment and guides future modelling of speciation phenomena of weak electrolytes. We extend the SAFT-VRE Mie equation of state [D. K. Eriksen et al., Mol. Phys., 2016, 114, 2724–2749] to study aqueous solutions of nitric, sulphuric, and carbonic acids, considering complete and partially dissociated models. In order to incorporate the dissociation equilibria, correlations to experimental data for the relevant thermodynamic equilibrium constants of the dissociation reactions are taken from the literature and are imposed as a boundary condition in the calculations. The models for water, the hydronium ion, and carbon dioxide are treated as transferable and are taken from our previous work. We present new molecular models for nitric acid, and the nitrate, bisulfate, sulfate, and bicarbonate anions. The resulting framework is used to predict a range of phase behaviour and solution properties of the aqueous acids over wide ranges of concentration and temperature, including the degree of dissociation, as well as the activity coefficients of the ionic species, and the activity of water and osmotic coefficient, density, and vapour pressure of the solutions. The SAFT-VRE Mie models obtained in this manner provide a means of elucidating the mechanisms of association and ion pairing in the systems studied, complementing the experimental observations reported in the literature.

scholarly journals Ion pairing and phase behaviour of an asymmetric restricted primitive model of ionic liquids

2016 ◽  
Vol 145 (23) ◽  
pp. 234510 ◽  
Author(s):  
Hongduo Lu ◽  
Bin Li ◽  
Sture Nordholm ◽  
Clifford E. Woodward ◽  
Jan Forsman
Keyword(s):  
Ionic Liquids ◽  
Ion Pairing ◽  
Phase Behaviour ◽  
Primitive Model ◽  
Restricted Primitive Model

Phase behaviour and solution properties of sulphobetaine polymers

Polymer ◽  
1986 ◽  
Vol 27 (11) ◽  
pp. 1734-1742 ◽  
Author(s):  
D.N. Schulz ◽  
D.G. Peiffer ◽  
P.K. Agarwal ◽  
J. Larabee ◽  
J.J. Kaladas ◽  
...  
Keyword(s):  
Phase Behaviour ◽  
Solution Properties

Weak electrolyte permeation in alimentary epithelia

1981 ◽  
Vol 240 (3) ◽  
pp. G191-G198
Author(s):  
M. J. Jackson ◽  
C. Y. Tai ◽  
J. E. Steane
Keyword(s):  
Mathematical Model ◽  
Alimentary Tract ◽  
Important Determinant ◽  
Potential Significance ◽  
Degree Of Ionization ◽  
Weak Electrolyte ◽  
Electrolyte Absorption ◽  
Weak Electrolytes ◽  
Discrimination Coefficient

The potential significance of ionized species in weak electrolyte absorption or secretion has been reexamined using a mathematical model that represents the epithelium as a system of parallel ion-permeable and ion-impermeable channels. An important determinant of weak electrolyte movement in this system is the ratio of ionized and nonionized permeabilities (Pi/Pni). This variable, which has been termed the discrimination coefficient, interacts with the degree of ionization in determining the contributions of ionized and nonionized species to the transepithelial movement of a weak electrolyte. Calculations based on the model suggest that ionized species may contribute significantly to the absorption or secretion of many common weak electrolytes. It is concluded that the frequently made assumption that ionized species do not contribute significantly to transepithelial movements of weak electrolytes in the alimentary tract is not generally valid. Further work is required to delineate the quantitative determinants of discrimination in alimentary epithelia, and two methods for evaluation of epithelial discrimination coefficients are described.

scholarly journals Intestinal transport of weak electrolytes: Determinants of influx at the luminal surface.

1978 ◽  
Vol 71 (3) ◽  
pp. 301-327 ◽  
Author(s):  
M J Jackson ◽  
A M Williamson ◽  
W A Dombrowski ◽  
D E Garner
Keyword(s):  
Cell Surface ◽  
Ph Value ◽  
Fluid Layer ◽  
Bulk Phase ◽  
Unstirred Layer ◽  
Epithelial Surface ◽  
Degree Of Ionization ◽  
Weak Electrolyte ◽  
Weak Electrolytes ◽  
Rate Limiting

The determinants of weak electrolyte influx into everted segments of rat small intestine have been studied. Preliminary experiments showed that the observed influxes could be described as unidirectional, diffusional fluxes of the nonionized compound uncomplicated by a parallel ionic component. It is shown that the determinants of weak electrolyte influx in this situation may be described in terms of the resistance of the unstirred layer to movement from the bulk phase to the cell surface, the degree of ionization of the weak electrolyte at the cell surface, and the cellular permeability to the nonionized weak electrolyte. Quantitative considerations indicated that the unstirred layer was totally rate-limiting in the cases of some poorly ionized, or highly permeant compounds, but the unstirred layer was not totally rate limiting for most of the compounds studied. Calculation of cellular permeabilities for the nonionized forms of weak electrolytes required assumptions to be made concerning the pH value in the surface fluid layer. A uniform set of permeability data including both weak acids and weak bases was obtained only when it was assumed that the pH in the surface fluid layer was equal to that in the bulk phase, and it was concluded that these studies do not support the concept of a microclimate of distinctive pH at the epithelial surface as a determinant of weak electrolyte transport.

Observations of Frozen-Hydrated Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 504-505
Author(s):  
D. Chrétien ◽  
D. Job ◽  
R.H. Wade
Keyword(s):  
Fourier Transforms ◽  
Structural Complexity ◽  
Image Contrast ◽  
Phase Behaviour ◽  
Experimental Conditions ◽  
Thin Sections ◽  
Surface Lattice ◽  
Cilia And Flagella ◽  
Outstanding Question

Microtubules are filamentary structures found in the cytoplasm of eukaryotic cells, where, together with actin and intermediate filaments, they form the components of the cytoskeleton. They have many functions and show various levels of structural complexity as witnessed by the singlet, doublet and triplet structures involved in the architecture of centrioles, basal bodies, cilia and flagella. The accepted microtubule model consists of a 25 nm diameter hollow tube with a wall made up of 13 paraxial protofilaments (pf). Each pf is a string of aligned tubulin dimers. Some results have suggested that the pfs follow a superhelix. To understand how microtubules function in the cell an accurate model of the surface lattice is one of the requirements. For example the 9x2 architecture of the axoneme will depend on the organisation of its component microtubules. We should also note that microtubules with different numbers of pfs have been observed in thin sections of cellular and of in-vitro material. An outstanding question is how does the surface lattice adjust to these different pf numbers?We have been using cryo-electron microscopy of frozen-hydrated samples to study in-vitro assembled microtubules. The experimental conditions are described in detail in this reference. The results obtained in conjunction with thin sections of similar specimens and with axoneme outer doublet fragments have already allowed us to characterise the image contrast of 13, 14 and 15 pf microtubules on the basis of the measured image widths, of the the image contrast symmetry and of the amplitude and phase behaviour along the equator in the computed Fourier transforms. The contrast variations along individual microtubule images can be interpreted in terms of the geometry of the microtubule surface lattice. We can extend these results and make some reasonable predictions about the probable surface lattices in the case of other pf numbers, see Table 1. Figure 1 shows observed images with which these predictions can be compared.

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