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The influence of different salts on the lower critical solution temperature (LCST) of mixtures of propylene glycol propyl ether and of dipropylene glycol propyl ether with water was determined experimentally. It was observed that the temperature shifts follow precisely the same Hofmeister series for anions that was originally found for salting-in and salting-out effects for protein solutions. The results are similar to the observations found for mixtures of water with non-ionic surfactants. In the case of dipropylene glycol propyl ether mixtures with water, temperature dependent phase diagrams in the presence of one salting-in (NaSCN) and one salting-out (Na2SO4) salt were measured at a fixed salt concentration in water of 0.041 M. The results can be qualitatively understood by assuming a different hydrophobicity for both types of salts. They further hint at a strong degree of solute determined cooperative water structure.

The aim of this work is to develop a new generation of repellent products with a long-lasting protection based on a natural component, para-menthane-3,8-diol (PMD). The active is first rendered soluble in a surfactantless microemulsion (H(2)O/(i)PrOH/PMD) and then in classical microemulsions. The presence of self-associated nanostructures is detected by dynamic light scattering (DLS). A synergetic system of surfactants (Cremophor) RH40 and Texapon N70) is used. Additionally, 2-ethylhexane-1,3-diol and ethyl (-)-(S)-lactate are incorporated. The final product contains, as main components, 46% of H(2)O, 25% of (i)PrOH, 20% of non-H(2)O-soluble PMD, and only 4% of surfactants. Investigations of lasting protection on human volunteers are carried out using a cage test bioassay protocol and Aedes aegypti mosquitoes. A complete protection of 315 min is found on the test persons using the surfactantless microemulsion. An extension is observed with the final formulation to reach a mean of complete protection of 385 min. This study demonstrates that alternative formulations using a natural active instead of synthetic chemicals like N,N-diethyl-m-methylbenzamide (DEET) can be efficient for human protection against mosquitoes.

A variety of methods has been used for the study of lithium bromide solutions in acetonitrile yielding by their combination reliable information on different levels of approximation. Osmotic coefficients based on precise vapor pressure measurements are reproduced by CM (chemical model) and HNC (hypernetted chain) calculations and by BD (brownian dynamics) simulations. The results of neutron scattering experiments are treated with the help of HNC and BD methods. Hartree-Fock calculations on isolated LiBr pairs and solvated lithium ions yield reliable particle distances and reveal the geometry of the lithium solvation sphere.

La caracterisation des ions de petite taille et de faible charge en phase liquide continuent a faire l'objet d'un grand nombre d'etudes. Le present article resume la complexite de la tâche et decrit quelques progres recents realises sur les plans theorique et experimental. Quelques exemples illustrent l'importance d'une comprehension approfondie des proprietes des electrolytes ainsi que l'application des connaissances acquises dans certains domaines d'interet technologique.

The kinetics of enzyme-catalyzed alc. oxidn. has been measured in liq. water/ethanol/Brij 35 and water/1-pentanol/Brij 35 systems, essentially in the water-rich regions. For the ethanol systems it was found that the enzymic activity sharply decreases with increasing alc. concn. independently of the surfactant concn. between 0 and 22 mass %. In the case of the 1-pentanol systems the enzymic activity decreases also with increasing alc. concn., but this decrease can considerably be attenuated by adding increasing amts. of surfactant. To explain these results at the nanometer level, small-angle neutron-scattering (SANS) expts. have been carried out on these systems. The comparison of the scattering and the kinetic measurements suggests the following interpretation. In all cases, the enzymic activity depends on the concn. of the alc. in the aq. phase or in the aq. pseudophase contg. the enzyme. A certain amt. of alc. may be present in an org. pseudophase formed by direct micelles. In the case of the 1-pentanol systems the alc. participates in the structuration of the micelles and is concd. in the micelles, whereas in the case of the ethanol systems the alc. remains essentially in the aq. pseudophase and even destroys the micelles. These results suggest that in some cases enzymic activity can be used as a probe to detect some aspects of the mol. organization of a complex liq.

A piezoelectric vibration exciter for generating mechanical vibrations for the purpose of destructive material or specimen testing has two equally sized disk stacks, each with an even number of piezoceramic disks. A vibration armature serving as a clamping device for the test specimen is arranged between the two disk stacks in a stiff clamping frame having a bail and a base plate. The assembly containing the disk stacks and the vibration armature is clamped in position in the stiff clamping frame. The piezoceramic disks are energized with an AC voltage so that one disk stack will axially contract in phase with the voltage, while the other disk stack will axially expand. As a result, the vibration armature and the test specimen arranged between the disks reciprocate at the frequency of the AC voltage input.

Modelling of the thermodynamic properties of electrolyte solutions for industrial interestsThis work is aimed at providing a description of he thermodynamics properties of electrolyte solutions for industrial interests. The model used here is based on a previous study (N. Papaiconomou et al.) combining the Mean Spherical Approximation MSA (Mean Spherical Approximation) theory to describe long-range electrostatic interactions, with the popular model in chemical engineering, i.e. NRTL ( Nonrandom Two-Liquid), for the representation of short-range interactions. This previous description has been improved by adding the ionic solvation effect with the help of two distinct models : (a) Robinson and Stokes one which involves a constant solvation number vs. salt concentration, and (b) modellling of the thermodynamic of ionic solutions using a stepwise solvation equilibrium model. In addition to this work, we have attempted a description of VLE (Vapor-Liquid equilibria) for aqueous solutions in a wide range of temperature, 25°C to 100°C., Le présent travail se propose de décrire les propriétés thermodynamiques des solutions d'intérêt industriel. Notre modèle s'appuie sur un travail antérieur (N. Papaiconomou et al.), combinant la théorie Mean Spherical Approximation (MSA) pour décrire les interactions électrostatiques à longue portée et le modèle NRTL (très populaire en génie chimique), pour celles qui sont à courte portée. Par rapport à ce précédent travail, nous avons de plus pris en compte l'effet de solvatation ionique, à l'aide de deux modèles différents : (a) celui de Stokes et Robinson impliquant un nombre de solvatation constant (en fonction de la concentration du sel) ; (b) une solution procédant d'équilibre réactionnels avec les molécules d'eau, résultant en un degré de solvatation variant avec la concentration de sel. De plus, nous avons cherché à décrire les équilibres L-V pour des solutions aqueuses et de mélanges de solvants, pour des températures allant de 25°C à 100°C.