The temperature dependence of mercury saturated vapor pressure over the whole range of its liquid state

The Boltzmann distribution with normalization with respect to the boiling point was used to calculate the temperature dependence of vapor pressure, which included the temperature and heat of boiling only. A refined equation of mercury vaporizability with mutually consistent characteristics such as vapor pressure and the temperature and heat of boiling was obtained. The equation correctly described this dependence over the whole liquid state range, including the critical point.     

Molecular simulation of the shear viscosity and the self-diffusion coefficient of mercury along the vapor-liquid coexistence curve

In earlier work [G. Raabe and R. J. Sadus, J. Chem. Phys. 119, 6691 (2003)] we reported that the combination of an accurate two-body ab initio potential with an empirically determined multibody contribution enables the prediction of the phase coexistence properties, the heats of vaporization, and the pair distribution functions of mercury with reasonable accuracy. In this work we present molecular dynamics simulation results for the shear viscosity and self-diffusion coefficient of mercury along the vapor-liquid coexistence curve using our empirical effective potential. The comparison with experiment and calculations based on a modified Enskog theory shows that our multibody contribution yields reliable predictions of the self-diffusion coefficient at all densities. Good results are also obtained for the shear viscosity of mercury at low to moderate densities. Increasing deviations between the simulation and experimental viscosity data at high densities suggest that not only a temperature-dependent but also a density-dependent multibody contribution is necessary to account for the effect of intermolecular interactions in liquid metals. An analysis of our simulation data near the critical point yields a critical exponent of beta = 0.39, which is identical to the value obtained from the analysis of the experimental saturation densities.     

Viscosity Behaviors of Rapidly Curable Silica Sols

The viscosity behaviors of rapidly curable transparent silica aerogels, such as time at the onset point and the slope of viscosity increase, are investigated as functions of target density, water and catalyst content. Results were compared with the visually measured gel time. The effects of temperature and shear rate on the onset point and rate of the viscosity increase are also investigated with the selected samples. Experimental design and result analysis were also conducted using the Design of Experiment (DOE) method, and the Arrhenius relation was applied to predict the temperature dependence of viscosity. It is found that the target density and catalyst content played more important roles in determining gelation and viscosity behavior than water content did. As the target density increased, the gel time and the onset point appeared at significantly earlier times and the slope increased more rapidly, while there existed an optimum catalyst and water content for fast gelation and desirable viscosity behaviors. The temperature dependence of the viscosity behaviors of rapidly curable transparent silica sols can be expressed by the Arrhenius relation. The onset time of viscosity increase was little affected by the shear rate at a low shear rate range of up to 1.32 s⁻¹, and after that it linearly decreased with increasing shear rate, while the slope of viscosity increase continuously decreased with increasing shear rate. Overall, the viscosity measurement appears as a simple and reliable method for quantitatively measuring gel time, especially for the rapidly curable sol–gel process.     

The inflection point in the pressure dependence of viscosity under high pressure: a comprehensive study of the temperature and pressure dependence of the viscosity of propylene carbonate

The pressure dependence of the prototypical glass-former propylene carbonate has been investigated over a broad range of temperature and pressure that were inaccessible in previous investigations using dielectric spectroscopy. We find that the viscosity measurements validate the scaling relation, eta(T,V)=J(TV gamma), with a scaling parameter gamma close to that found from dielectric relaxation measurements. In the pressure dependence of the viscosity, we observe an inflection point in the log eta versus P response, similar to that found previously for other materials. However, this inflection has never been observed in dielectric relaxation measurements. Using the scaling property above, it is possible to determine the behavior of the dielectric relaxation time in this otherwise inaccessible experimental range and compare it with the viscosity measurements. We find that the behaviors of eta and tau are very similar, and a very good agreement between the function phi P calculated for these two quantities is found. Starting from the validity of the scaling properties, we show that the inflection point in the pressure dependence of the viscosity can be attributed to the convolution of the pressure dependences of the compressibility kappa T and the apparent activation energy at constant volume EV.     

Dependence of the viscosities of some organic aliphatic acids on temperature and molar volume

The viscosities of some aliphatic acids were measured in the vicinity of the melting point with a Höppler viscosimeter. The dependence of the viscosity on the molar volume permitted calculation of the covolume, which is compared to that obtained from structural data.     

Reduction of an Ensemble of Platinum(II) Aquachloride Complexes: Dynamic Effect of the Solvent

Dynamic effect of the solvent is studied for the first time ever for the process that occurs in the vicinity of the activationless region, namely, the reaction of electroreduction of an ensemble of platinum(II) aquachloride complexes on a negatively charged mercury electrode. A sequential analysis of the sucrose influence on the interface structure and the equilibrium solvation energy is performed. Estimates of the above effects are given. These are necessary for subtracting the dependence of the electron transfer rate on the solvent relaxation time from the observed overall dependence on the concentration of the viscosity-forming additive. A procedure for estimating the sucrose concentration in the reaction layer is suggested and on this basis the increase in the local viscosity near the interface, which is caused by the presence of a surface excess of sucrose, is approximately taken into account. The potential interval where the reaction under study occurs in an almost adiabatic mode is determined.     

Flow curves of an adsorbed protein layer at the saliva-air interface

At the air-liquid interface of human saliva a protein layer is adsorbed. An apparatus is described with which a flow curve of this layer was measured. In the majority of samples the viscosity of the surface layer changed gradually and could be described by a power-law dependence on the shear rate. The zero-shear viscosity was 1–100 MPa·s. In some saliva samples a sharp yield point was observed.     

Hydrophobic interactions between polymethacrylic acid and sodium laureth sulfate in aqueous solutions

The role of hydrophobic interaction in the development of associative processes is demonstrated, based on the concentration dependences of the viscosity and pH of binary solutions of polymethacrylic acid as an anionic polyelectrolyte and sodium laureth sulfate as an anionic surfactant. It is found that the inflection point on the dependence of the difference between the pH values of binary solutions of polymethacrylic acid and sodium laureth sulfate on the polyelectrolyte concentration is a criterion for determining the predominant contribution from hydrophobic interaction, as is the inflection point on the dependence of pH of individual solutions of polymethacrylic acid on the polyelectrolyte concentration.     

Membrane fluidity of tetramyristoyl cardiolipin (TMCL) liposomes studied by chronoamperometric monitoring of their adhesion and spreading at the surface of a mercury electrode

Giant unilamellar liposomes of the synthetic cardiolipin 1′,3′-bis[1,2-dimyristoyl-sn-glycero-3-phospho]-sn-glycerol give chronoamperometric current peaks at a stationary mercury electrode. The signals are due to the adhesion and spreading of the liposomes on the hydrophobic mercury surface. The potential dependence shows a minimum of the peak frequency at the point of zero charge, a large maximum of peak frequency at about ?0.2?V and a second, however, smaller maximum at ?0.8?V. The electrochemical behaviour of the liposomes indicates phase transitions of the cardiolipin which could be also observed in differential scanning calorimetry.     

Determination of Mercury Species in Human Urine by Gas Chromatography-Mass Spectrometry

Monitoring urine mercury levels is helpful to estimating the extent of occupational, environmental and everyday exposure to mercury. Furthermore,mercury speciation has received wide attention all over the world in the past decades because of the close dependence of the toxicity of mercury on its chemical species.     

Viscosities of liquid CdTe near melting point from ab initio molecular-dynamics calculations

Recent experimental results for the viscosity of liquid CdTe exhibit disparate behavior as a function of temperature. While some measurements show the expected Arrhenius-type behavior, other measurements show an anomalous temperature dependence indicating an increase in viscosity with increasing temperature. We present ab initio molecular-dynamics simulations of liquid cadmium telluride near its melting point and use the Stokes-Einstein relation to extract values of the viscosity constant. We find no anomalous behavior; the viscosity decreases monotonically with temperature and is consistent with an Arrhenius like behavior. Although calculated values are slightly smaller than those measured, the predicted activation energy agrees well with experiment.     

A microcalorimetric study of mercury(II) sorption on KU-2-8 sulfocationite

The thermokinetic characteristics of the sorption of mercury(II) ions on KU-2-8 strongly acidic cationite from mercury acetate solutions was studied using microcalorimetry. The overall heat of sorption and its dependence on the degree of filling of the cationite were determined.     

Primary electroviscous effect in a dilute suspension of charged mercury drops

The standard theory of the primary electroviscous effect in a dilute suspension of charged spherical rigid particles in an electrolyte solution (Watterson, I. G.; White, L. R. J. Chem. Soc., Faraday Trans. 2 1981, 77, 1115) is extended to cover the case of a dilute suspension of charged mercury drops of viscosity eta(d). A general expression for the effective viscosity or the electroviscous coefficient p of the suspension is derived. This expression tends to that for the case of rigid particles in the limit of eta(d) --> infinity. We also derive an approximate analytical viscosity expressions applicable to mercury drops carrying low zeta potentials at arbitrary kappaa (where kappa is the Debye-Hückel parameter and a is the drop radius) and to mercury drops as well as rigid spheres with arbitrary zeta potentials at large kappaa. It is shown that the large-kappaa expression of p for rigid particles predicts a maximum when plotted as a function of zeta potential. This result for rigid particles agrees with the exact numerical results of Watterson and White. It is also shown that in the limit of high zeta potential the effective viscosity of a suspension of mercury drops tends to that of uncharged rigid spheres given by Einstein's formula (Einstein, A. Ann. Phys. 1906, 19, 289), whereas in the opposite limit of low zeta potential the effective viscosity approaches that of a suspension of uncharged liquid drops derived by Taylor (Taylor, G. I. Proc. R. Soc. London, Ser. A 1932, 138, 41).     

Solvent viscosity dependence of the folding rate of a small protein: distributed computing study

By using distributed computing techniques and a supercluster of more than 20,000 processors we simulated folding of a 20-residue Trp Cage miniprotein in atomistic detail with implicit GB/SA solvent at a variety of solvent viscosities (gamma). This allowed us to analyze the dependence of folding rates on viscosity. In particular, we focused on the low-viscosity regime (values below the viscosity of water). In accordance with Kramers' theory, we observe approximately linear dependence of the folding rate on 1/gamma for values from 1-10(-1)x that of water viscosity. However, for the regime between 10(-4)-10(-1)x that of water viscosity we observe power-law dependence of the form k approximately gamma(-1/5). These results suggest that estimating folding rates from molecular simulations run at low viscosity under the assumption of linear dependence of rate on inverse viscosity may lead to erroneous results.     

Negative flow activation energy of polymer solutions

Using equations which describe the concentration dependence of the specific viscosity of polymer solutions and the temperature dependence of intrinsic viscosity and of the Huggins viscosity parameter, conditions were sought for which solution viscosity increases with temperature (flow activation energy is negative). It was found that such an effect might appear near to the θ-temperature (regardless of the θ-temperature being LCST or UCST) particularly for polymers with high molecular weight. The concentration range depends on the system being endo- or exothermal. The conclusions are in agreement with experimental results.     

Orientational–deformational nature of flow birefringence in solutions of rigid-chain polymers

The orientational–deformational nature of flow birefringence (FB) in solutions of rigid-chain polymers is confirmed experimentally. The possibility of a direct determination of the internal viscosity parameter by the dependence of the FB relaxation time on the solvent viscosity is demonstrated. Indirect manifestation of internal viscosity in the FB relaxation time is confirmed by the dependence of the form factor on the degree of coiling. © 1993 John Wiley & Sons, Inc.     

Influence of molecular characteristics of nonionic cellulose ethers on their interaction with ionic surfactant investigated by conductometry

The interaction between nonionic derivatives of cellulose, hydroxypropylmethyl cellulose (HPMC) and methyl cellulose (MC), and ionic surfactant, sodium dodecylsulfate (SDS) were investigated by conductometric titration method, at 30°C. Obtained titration curves show two break points: critical aggregation concentration (cac) defined as the concentration of SDS at which interaction starts, and polymer saturation concentration (psp) as the concentration at which interaction finishes. Changes of characteristic concentration breaks were determined in dependence on concentration and molecular characteristics of cellulose derivatives (degree of substitution (DS) and molecular mass, i.e. intrinsic viscosity). It was shown that the first break point, cac, is independent of polymer concentration; while the second break point, psp, increases as polymer concentration increases, as described by a linear correlation. The slopes of linear relationship justify the DS on the intensity of the cellulose derivatives–SDS interaction. Changes in the intrinsic viscosity of cellulose derivatives do not exhibit influence on the interaction with SDS.     

Molecular structures of thimerosal (Merthiolate) and other arylthiolate mercury alkyl compounds

The molecular structure of sodium ethylmercury thiosalicylate (also known as thimerosal and Merthiolate) and related arylthiolate mercury alkyl compounds, namely PhSHgMe and PhSHgEt, have been determined by single crystal X-ray diffraction. (1)H NMR spectroscopic studies indicate that the appearance of the (199)Hg mercury satellites of the ethyl group of thimerosal is highly dependent on the magnetic field and the viscosity of the solvent as a consequence of relaxation due to chemical shift anisotropy.     

Viscosity of liquid suspensions with fractal aggregates: Magnetic nanoparticles in petroleum colloidal structures

New physical model is presented resulting in a simple formula for the dependence of viscosity η of colloidal liquid solution on the shear rate G applicable to a wide variety of systems including complex natural liquids like petroleum. The principal point of the model is the fractal nature of colloid particle aggregates present in the liquid. Such aggregates are experimentally detected now in non-Newtonian liquids. The model is based on calculation of energy loss on colloidal particle aggregate of fractal structure localized in the flow of liquid with shear rate. We have performed the viscosity measurement experiments which confirmed successfully the developed physical model. Also, we demonstrate experimentally that petroleum colloidal particles and magnetic iron oxide nanoparticles can form composite fractal-like aggregates in natural petroleum materials. Our model can explain both the non-Newtonian properties of petroleum and sensitivity of petroleum viscosity to external magnetic fields.