Capillary constant and surface tension of methane-nitrogen solutions: 1. Experiment

The differential version of the method of capillary rise has been used to measure the capillary constant and calculate the surface tension of methane-nitrogen solutions. Experiments have been conducted in the temperature range from 95 to 170 K at pressures up to 4 MPa. Experimental data on surface tension have been compared with the results of calculations by thermodynamic models. Equations are given which describe the dependence of the capillary constant of a solution on its temperature and composition.     

Experimental study of surface tension of ethane-methane solution in temperature range 213–283 K

The differential variation of the method of capillary rise was used to measure the capillary constant and to determine the surface tension of ethane-methane solution at “high” temperatures. Measurements were performed on the isotherms in the range of temperatures 213.15 ÷ 283.15 K at pressures up to 4 MPa. Decrease of ethane surface tension with the increase of pressure and concentration of methane in the solution is shown. The experimental data are compared with the results of surface tension calculation according to Rowlinson theory. Methane adsorption in the interface layer of solution is calculated.     

The liquid–gas interface of oxygen–nitrogen solutions: 1. Surface tension

The capillary method of surface tension measurement has been used to measure the surface tension of oxygen–nitrogen solutions in the temperature range from 80 to 132 K. At temperatures below the nitrogen critical temperature (T_c = 126.2 K) the capillary constant and the surface tension of solutions are smaller than their additive values and vary linearly with the temperature. Experimental data are compared with the results of calculating the surface tension by the theories of Pinnes and Rowlinson.     

Quantifying uncertainty in the measurement of arsenic in suspended particulate matter by Atomic Absorption Spectrometry with hydride generator

Arsenic is the toxic element, which creates several problems in human being specially when inhaled through air. So the accurate and precise measurement of arsenic in suspended particulate matter (SPM) is of prime importance as it gives information about the level of toxicity in the environment, and preventive measures could be taken in the effective areas. Quality assurance is equally important in the measurement of arsenic in SPM samples before making any decision. The quality and reliability of the data of such volatile elements depends upon the measurement of uncertainty of each step involved from sampling to analysis. The analytical results quantifying uncertainty gives a measure of the confidence level of the concerned laboratory. So the main objective of this study was to determine arsenic content in SPM samples with uncertainty budget and to find out various potential sources of uncertainty, which affects the results. Keeping these facts, we have selected seven diverse sites of Delhi (National Capital of India) for quantification of arsenic content in SPM samples with uncertainty budget following sampling by HVS to analysis by Atomic Absorption Spectrometer-Hydride Generator (AAS-HG). In the measurement of arsenic in SPM samples so many steps are involved from sampling to final result and we have considered various potential sources of uncertainties. The calculation of uncertainty is based on ISO/IEC17025: 2005 document and EURACHEM guideline. It has been found that the final results mostly depend on the uncertainty in measurement mainly due to repeatability, final volume prepared for analysis, weighing balance and sampling by HVS. After the analysis of data of seven diverse sites of Delhi, it has been concluded that during the period from 31^st Jan. 2008 to 7^th Feb. 2008 the arsenic concentration varies from 1.44 ± 0.25 to 5.58 ± 0.55 ng/m³ with 95% confidence level (k = 2).     

Surface tension at the boundaries of helium-argon and neon-argon solutions at 108–140 K

The capillary constant was measured and surface tension determined for helium-argon and neon-argon solutions by the differential version of the capillary rise method over the temperature range 108–140 K at pressures up to 4 MPa. The adsorption of helium and neon in interfacial solution layers was calculated.     

The liquid–gas interface of oxygen–nitrogen solutions 2: Description in the Framework of the van der Waals gradient theory

The van der Waals gradient theory (vdW GT) is used to calculate surface tension, density profiles, adsorption, the Tolman length and to determine the position of dividing surfaces in the liquid–gas interface of an oxygen–nitrogen solution. The Helmholtz energy density (HED) is determined via an equation of state (EOS), unified for a liquid and gas, which describes stable, metastable and two-phase states of solutions. The influence parameters are calculated from data on the surface tension of pure components with the use of the mixing rule. At temperatures T > 100 K the vdW GT describes experimental data on the surface tension of oxygen–nitrogen solutions [V.G. Baidakov, A.M. Kaverin, V.N. Andbaeva, The liquid–gas interface of oxygen–nitrogen solutions: 1. Surface tension, Fluid Phase Equilib. 270 (2008) 116–120] within the experimental error. It is shown that the Tolman length, which determines the dependence of surface tension on the curvature of the dividing surface, depends considerably on the solution concentration.     

Structural characteristics of different types of nanoparticles synthesised in mesomorphic metal alkanoates

The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC₈) and of the cobalt octanoate (CoC₈). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained.     

Boiling-up of liquid argon at high superheatings under the impact of weak ultrasonic fields

The technique of lifetime measurement for metastable liquid and continuous depressurization technique were applied for study of kinetics of spontaneous cavitation in superheated liquid argon under impact of weak ultrasonic fields. It was demonstrated that acoustic cavitation may occur through the mechanism of homogeneous generation of vapor phase or through “swinging” of vapor bubbles generated by high-energy particles and/or other kinds of initiative factors. The thresholds of acoustic cavitation are described by the theory of homogeneous nucleation.     

Attainable superheat of argon-helium, argon-neon solutions

The method of lifetime measurement has been used to investigate the kinetics of spontaneous boiling-up of superheated argon-helium and argon-neon solutions. Experiments were made at a pressure of p = 1.5 MPa and concentrations up to 0.33 mol% in the range of nucleation rates from 10 (4) to 10 (8) s (-1) m (-3). The homogeneous nucleation regime has been distinguished. With good agreement between experimental data and homogeneous nucleation theory in temperature and concentration dependences of the nucleation rate, a systematic underestimation by 0.25-0.34 K has been revealed in superheat temperatures over the saturated line attained by experiment as compared with theoretical values calculated in a macroscopic approximation. The revealed disagreement between theory and experiment is connected with the dependence of the properties of new-phase nuclei on their size.