Studies on the Interactions of Paracetamol in Water and Binary Solvent Mixtures at T = (298.15–313.15) K: Viscometric and Surface Tension Approach

Temperature, concentration, and solvent conditions have consequences on the formation and dissolution of the drug. Viscometric measurements of paracetamol solutions of different concentrations in 5, 10, and 15% methanol have been made at 298.15, 303.15, 308.15, and 313.15K. Surface tension values (γ) of the solutions were obtained experimentally by using a stalagmometer as well as were derived from the ultrasonic velocity (U) and density (d) values at 298.15 K. The surface tension data have been analyzed using the Gibbs equation to evaluate surface excess (Γ_2). The surface tension and surface excess data obtained by the two different methods are well in accordance. The viscosity (ɳ) data were used to calculate relative viscosity (ɳ_(r ) ), Falkenhagen coefficients (A_(F )), Jone-Dole’s coefficients (B_(J ) ) and chemical potential (μ). The obtained data have been analyzed based on the Jones-Dole equation to know the molecular interactions.

Novel Method for Surface Tension Measurement: the Drop-Bounce Method

The surface tension of liquids at high temperatures is generally measured with the well-established oscillating drop method in a contactless environment. However, technical difficulties in surface tension measurements make it hard to apply the oscillating drop method to the aerodynamic levitation (ADL) system, the most reliable levitation technique for liquids with low electrical conductivity. In this study, we developed a novel drop–bounce method that can be used within an ADL system to measure the surface tension of liquids. A levitated molten sample was first dropped onto an inert substrate through a splittable nozzle. The rebounded sample’s oscillatory motion behaved as it would under microgravity conditions during its free-fall, and oscillations were obtained only in the l=2, m=0 mode. Fourier transformation of the oscillation pattern provided resonant frequency of the l=2, m=0 mode and enabled the calculation of the surface tension of the sample under knowledge of its mass. Furthermore, a short experimental duration of less than 50 ms significantly reduced the possibility of surface evaporation in the sample. Our measured surface tension data from 1354 K to 1827 K for gold exhibited a standard deviation of 13.4 mJ/m2 and were consistent with the data published by Egry et al. under microgravity conditions, with a maximum deviation of 1.5% between the two fitted linear equations.

Study on the Interaction of Cationic Gemini Surfactant with Sodium Carboxymethyl Cellulose

In the present study, the interaction of the anionic polymer sodium carboxymethyl cellulose (NaCMC) with the two cationic gemini surfactant (C12-(EO)-E-C12 and C12-(EO)2-E-C12) has been investigated by surface tension and turbidity measurements. The co-adsorption of the polymer and the surfactants as well as the formation of highly surface-active polymer-surfactant complex was observed. By inserting the surface tension data into the Gibbs equation it could be shown that the surface layers of the mixed solutions have a multi-level adsorption structure. Comparing the critical adsorption concentration (C1), the critical saturation concentration (C2) and the critical micelle formation concentration (C3) of mixtures with different concentrations, it can be seen that all variables increase with the increase in polymer concentration. In addition, the inorganic salt (NaBr) greatly influences the C1, C2 and C3. The salt effects depend on the competition between the salt-enhancing effect and the salt-shielding effect.

Critical Synergistic Concentration of Binary Surfactant Mixtures

This paper presents a simple method for determination of synergism in binary surfactant mixtures. A homologous series of cationic alkyltrimethylammonium bromides (CnTAB, with n = 8, 12, 16, 18) mixed with three non-ionic surfactants (n-octanol, methyl isobutyl carbinol, tri(propylene glycol) butyl ether) was chosen as a model system. In addition to the cationic-non-ionic system, the mixture of anionic-non-ionic surfactants (sodium dodecyl sulphate and tri(propylene glycol) butyl ether) was investigated. The foam behavior of one-component solutions and binary mixtures was characterized as a function of surfactant concentration, number of carbons (n) in alkyl chain of CnTAB as well as type of surfactant. It was shown that synergism in foamability could be produced by the ionic-non-ionic systems, and the concentration below the synergism occurs, called the critical synergistic concentration (CSC), that can be easily predicted based on the surface tension data on individual components.

Adsorption Kinetics of a Cationic Surfactant Bearing a Two-Charged Head at the Air-Water Interface

We studied the dynamics of adsorption at the air-water interface of a cationic surfactant bearing two charges, Gemini 12-2-12, at concentrations below and above the critical micelle concentration (cmc). We used maximum bubble pressure and Wilhelmy plate techniques in order to access all time scales in the adsorption process. We found that the adsorption dynamics are controlled by diffusion at the initial stage of the adsorption process (milliseconds) and it is kinetically controlled by an electrostatic barrier (minute) approaching the equilibrium surfactant surface concentration. Between these two extremes, we found several relaxation phenomena, all following exponential decays with characteristic times spanning from one to hundreds of seconds. By means of time-resolved surface potential measurements, we show that these processes involve charge redistribution within the interfacial region. The surface tension data are analyzed and interpreted in the framework of the free energy approach.

Surface tension of liquid nickel: Re-evaluated and revised data

Nickel is an important component in many alloys, so reliable surface tension data in the liquid phase are essential for simulation processes in the metal industry. First results for surface tension of liquid nickel from our working group by Aziz et al. [1], which led to the first publication on the topic of our Electromagnetic Levitation (EML) setup, delivered unusual high values compared to the literature, which itself covers a wide range. To find the reason for this behaviour the aim of this work was to investigate the surface tension of nickel samples from different suppliers at similar purity grades by the Oscillating Drop (OD) technique using the EML setup of the Thermophysics and Metalphysics Group at Graz University of Technology. Since no significant deviations between samples from different suppliers have been found, an extensive literature research according to various experimental and evaluation parameters has been performed. In the course of this investigation, the earlier obtained experimental data of Aziz et al. were re-evaluated. Due to gained awareness in evaluating the translational frequency in vertical direction, the mystery of these elevated surface tension results could be solved, so that in the end the originally obtained results of Aziz have been drastically decreased through re-evaluation.

Physicochemical and thermodynamic properties of solutions of clary sage (Salvia sclarea L.) essential oil in ethanol-water system

Clary sage (Salvia sclarea L.) essential oil-ethanol-water system was investigated. The surface tension, density and refractive index of clary sage essential oil + ethanol (70%, 75%, 80%, 85%, 90%, and 95%) solutions were measured. The chemical composition of solutions (ratio 1:5, 1:6, and 1:7) was determined using GC/MS analysis. According the experimental results ternary phase diagrams were constructed. Comparative revue between experimental and calculated surface tension data was done. After analyses good correlation between two surface tension values was observed