Colloid-chemical properties of 1,1-dimethyl-1-alkylhydrazinium chlorides

The colloid-chemical properties [surface tension, surface activity, and critical micellization concentration (CMC)] of aqueous 1,1-dimethyl-1-alkyl(R)hydrazinium chlorides (R = C₁₀H₂₁–C₁₈H₃₇) were studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1861–1864.Original Russian Text Copyright © 2004 by Shcherban, Radushev, Nasretdinova, Teterina, Bubyakina.     

Physicochemical properties of 1,1-dimethyl-1-alkylhydrazinium chlorides

With the aim of widening the applications of 1,1-dimethyl-1-alkylhydrazinium chlorides, the physicochemical properties (solubility, hygroscopicity, thermal and chemical stability, distribution between aqueous and organic phases) of their homologs with the alkyl radicals C₁₀H₂₁-C₁₈H₃₇ were studied.     

Surface-active properties of a series of 1,1-dimethyl-1-alkylhydrazinium chlorides

The surface-active properties of a series of 1,1-dimethyl-1-alkylhydrazinium chlorides with C₁₀–C₁₈ in length were studied in comparison with Neonol AF 9–12 and Oksifos B surfactants. The limiting wetting angle, detergent and solubilization power, and foaming kinetics of these surfactants were studied in relation to the concentration of formation of monomolecular layer and type of the resulting micellar structures.     

Ionic association in aqueous solutions of strong electrolytes

A more accurate calculation of relaxation effects obtained with the standard Debye-Hückel-Onsager model has been presented recently and is here applied to several aqueous 1:1 electrolytes. The variation of the standard deviation between calculated and observed equivalent conductivities withK _A leads to an ill-defined minimum; but, where data over a wide concentration range are available, the minimum corresponds to values of the contact distancea which approximate to estimates from ionic dimensions. It is therefore proposed that, although preciseK _A values from conductance cannot be determined, the most probable values are those associated with realistic estimates ofa. When data cover a limited concentration range, minimum standard deviations are often indeterminate or vary greatly for duplicate runs. It is shown that reasonable values ofK _A can be obtained from such data if comparison is made at estimated values ofa.Notation The symbols not defined in the text are the following b e ²/kTa for 1:1 electrolytes - e electronic charge - k Boltzmann gas constant - T absolute temperature - dielectric constant of solvent - –(3/2y)(_e0/₀)     

Effect of electrolytes on surface tension and surface adsorption of 1-hexyl-3-methylimidazolium chloride ionic liquid in aqueous solution

Surface and bulk properties of 1-hexyl-3-methylimidazolium chloride [C₆mim][Cl] as an ionic liquid (IL) have been investigated by surface tension and electrical conductivity techniques at various temperatures. Results reveal that the ionic liquid behaves as surfactant-like and aggregates in aqueous solution. Critical aggregation concentration (cac) values obtained by conductivity and surface tension measurements are in good agreement with values found in the literature. A series of important and useful adsorption parameters including cac, surface excess concentration (Γ), and minimum surface area per molecule (A_min) at the air + water interface were estimated from surface tension in the presence and absence of different electrolytes. Obtained data show that the surface tension as well as the cac of [C₆mim][Cl] is reduced by electrolytes. Also, values of surface excess concentration (Γ) show that the IL ions in the presence of electrolyte have much larger affinity to adsorption at the surface and this affinity increased in aqueous electrolyte solution in the order of I^? > Br^? > Cl^? for counter ion of salts that was explained in terms of a larger repulsion of chloride anions from interface to the bromide and iodide anion as well as difference in their excess polarizability.     

Regularity of conductivity of concentrated aqueous solutions of strong electrolytes

Conductivity of concentrated aqueous solutions of strong electrolytes is analyzed in a wide range of temperatures and concentrations. The highest conductivity of solutions at a given temperature and the concentration corresponding to the highest conductivity are used as the generalizing parameters. It is shown that in the temperature range from 0 to 100°C and the concentration range from 0.1 to 12 M, the values of reduced conductivity (the ratio between the conductivity and its maximum value at a given temperature) for KOH aqueous solution fall on a common curve, if the reduced concentration (the ratio between the concentration of solution and the concentration corresponding to the highest conductivity) is used as the argument. The reduced conductivities of strong acids, bases, and salts of some I-I, I-II, II-I, III-I, and II-II electrolytes fall on the same curve.     

Prediction of activity coefficients of electrolytes in aqueous mixed electrolyte solutions

A method is proposed for calculating the activity coefficient of constituent electrolytes in aqueous mixed electrolyte solutions. The equations derived from the knowledge of Λ^*, the overall reduced ionic activity coefficient in a mixture, are found to predict activity coefficients accurately up to an ionic strength of 12 mol kg⁻¹ and a temperature of 473 K.     

The activity of water and permittivity of aqueous solutions of electrolytes

The relation between concentration changes in the activity of water (a _w) and static permittivities (ɛ) of concentrated solutions of salts was studied over a wide concentration range. The dependence of a _w on 1/ɛ was shown to be linear at 298 K for more than 15 examples. The concentration boundary of the first structural zone of solutions where this dependence was observed was established. The appearance of deviations was related to concentrations at which complex ion-water groups were present in solutions and the transition from a water-electrolyte to an electrolyte-water solvent occurred.     

Micellization and surface activity ofn-alkyldimethylaminopropanesulfonates in aqueous solutions

Surface tension experiments were performed on severaln-alkyldimethylaminopropanesulfonate aqueous solutions at 15°, 25°, and 35°C. The critical micellar concentrations have been obtained and the surface properties calculated. The enthalpic and entropic contributions to either micellization and adsorption processes have been discussed. The observed properties have been related to the zwitterionic character of these surfactants.     

Single ion activity coefficients in concentrated aqueous hydrogen chloride solutions

The adsorption behaviour of the steroids: ouabagenin, ouabain, proscillaridin, digoxin, and k-strophanthine was studied by a.c. polarography and capacitance—time curves at the dropping mercury electrode. The steroids behave like strongly surface-active substances: the relative capacitance decrease ΔC/C₀ depends linearly both on the concentration of the solution and on the root of the drop age. The surface area determined for ouabagenin to be 125 Ų on the basis of adsorption kinetics corresponds roughly to the maximum crosssection of the molecule. With glycosides, the surface area increases with the number of monosaccharide molecules being attached in position 3 of the steroid. It was inferred, therefore, that the adsorbed molecule rests with its steroid and sugar moiety flat on the electrode. A capacitance minimum with sharply defined edges (pit) occurs in the a.c. polarograms of ouabain. In this potential area, the dependences Δ/₀=f(c) and ΔC/C₀=f(t) show a step-like course with two plateaus, which is discussed to be due to association of the adsorbed molecules.     

Note on the theory of solutions of strong electrolytes

Summary In the general case, assumptions of an increase in the average diameter of ions and hydration numbers with temperature contradict experiment. To explain the positive deviations of experimental heats of dilution from the Debye-Hückel theory, it is necessary to consider the existence of ionic pairs in solution and changes in the solution structure with concentration.     

Ion hydration effects in aqueous solutions of strong electrolytes,according to proton magnetic relaxation measurements

The concentration dependences of proton magnetic relaxation (PMR) rates measured at different temperatures in aqueous electrolyte solutions and concentrated seawater (SW) in a wide range of salt concentrations and for different seawater salinities are presented, along with the concentration dependences of PMR rates determined in salts dissolved directly in seawater. The coordination numbers of the basic ions in seawater were determined from the complete solvation limits and compared with those measured in single-component water-salt solutions. The attaining of complete solvation limits was determined using the PMR data for ions of different hydration signs.     

Modeling aqueous electrolyte solutions: Part 1. Fully dissociated electrolytes

Liquid densities (pvT), vapor pressures (VLE), and mean ionic activity coefficients (MIAC) at 25 °C of 115 single-salt electrolyte solutions containing univalent up to trivalent ions are modeled with the ePC-SAFT equation of state proposed by Cameretti et al. [L.F. Cameretti, G. Sadowski, J.M. Mollerup, Ind. Eng. Chem. Res. 44 (2005) 3355–3362; ibid., 8944]. For each ion, only two model parameters were adjusted to experimental density and MIAC data. Without using any additional binary parameters, ePC-SAFT is able to reproduce experimental data of the respective salt solutions up to high electrolyte molalities. Moreover, it is even able to describe the reversed MIAC series for alkali hydroxides and fluorides.