Positron Annihilation in and Adiabatic Compressibility of Water-Organic Solutions. The System Water-Dimethylsulfoxide

Abstract

The results of positron lifetime and ultrasonic velocity measurements in dilute aqueous dimethylsulfoxide (DMSO) solutions show the usual extreme characteristic for polar organic solutes. The results obtained suggest that strong structural changes occur in the system, in the region of low DMSO concentrations. Liquid clathrate hydrates forming in the systeni are supposed, with unusual stoichiometry and untypical geometry of the hydrates.PACS numbers: 61.25. Em, 78.70.Bj It is a well established fact now that the thermodynamic properties of aqueous solutions of apolar compounds or molecules having both polar and polar components (polar organic molecules) at low concentrations are predominantly determined by hydrophobic interactions which result in an enhancement of water structure. The stabilization of water stucture also gets support by NMR [1] and infrared spectroscopy [2], by X-ray diffractions [3] as well as by studies on molecular dynamics [4].Because of the fact that many of these organic compounds form clathrate hydrates in the solid state, attempts to explain the characteristic behaviour of liquid solutions in terms of clathrate-like structures seem to be more legitimate than interpretations based on other concepts.

Positron Annihilation in and Adiabatic Compressibility of Ethylene Glycol Aqueous Solutions

“…20°C) with a standard measuring device based on the "fast-slow" coincidence technique as described elsewhere [11].…”

Structure of Cyclohexane + t-Butanol Mixtures from Positron Annihilation and Ultrasonic Velocity Measurements

“…The lifetimes of positrons and positronium were measured using a standard system based on the "fast-slow" coincidence technique and described in details in [1]. The annihilation experiment was performed at room temperature (approximately 25°C).…”

“…The details about data treatment can be found in [1]. The obtained values of τl , τ2 and I2 are plotted in Fig.…”

“…Previously, we tried to compare the ultrasonic results of measurements carried out on aqueous solutions of non-electrolytes (amines and alcohols) with those from positron annihilation experiment (see for example [1,2]). It was found that both techniques applied, although different, led to consistent results explainable within the framework of liquid pseudoclathrate stuctures.…”

Structure of Carbon Tetrachloride + t-Butanol Mixtures from Positron Annihilation and Ultrasonic Velocity Measurements

“…The lifetimes of positrons in the liquids were measured using a standard system based on the "fast-slow" coincidence technique and described in details in [1]. The annihilation experiment was performed at room temperature (approximately 25°C).…”