Ultrasonic Studies of Aqueous Solutions of Non-electrolytes

Abstract

Absorption measurements were made in the ranges 1.5 to 230 Mc/sec and 0° to 45°C at various concentrations. Diethylamine solutions showed single-relaxation behavior, attributed to complex formation by hydrogen bonding. Absorption attributed to separation of phases near the lower critical solution temperature was shown in addition by triethylamine solutions. In methyl diethylamine solutions (L.C.S.T.=49°C), the transition from single- to double-relaxation behavior arising from these 2 mechanisms was observed. The absorption by n-amylamine solutions was compared with that by n-octylamine solutions, which form micelles. dμmax/dc decreased sharply at the critical micelle concentration. (μmax=maximum absorption per wavelength, c=concentration). Nine further solutes with hydrogen-bonding sites were studied. In each, the concentration for peak sound absorption (PSAC) was less than 0.5 MF, showing that more than one water molecule was associating with each solute molecular. Empirical relations between PSAC, relaxation frequency, and molecule weight were obtained. Quantitative interpretation of the measurement has been attempted in terms of models allowing for successive addition of water molecules to a complex and for breakdown of the water structure. Limiting values of bond energies, applicable to completely isothermal and adiabatic conditions, were calculated, but meaningful intermediate conditions could not be determined.

Kinetics of the solvolysis of [Co(3Rpy)4Cl2]+ (R = Me or Et) in water + propan‐2‐ol mixtures

“…0.2, than for those observed in water + methanol. It is noteworthy that the first of these extrema (and the only one for [C0(3Mepy)~Cl~] +) occurs at a mol fraction of propan-2-01 which corresponds closely with that where the sharp minimum in % -V, O occurs [12], and the second extremum for [Co(3Etpy),Clz]+ occurs at about the same mol fraction of propan-2-01 as where the maximum in the ultrasonic absorption occurs [14]. As these extrema in the physical properties are usually taken to indicate situations where sharp changes occur in the solvent structure, with the lower x 2 probably indicating where the maximum struc- ture formation has been induced [20] within the Frank-type "ice-bergs" of structured water sulting probably in the onset of the breakdown of the structure of the "icebergs" [20], these correlations support the suggestion that changes in solvent structure influence the rates of solvolysis.…”

“…0.04 [12], the positive structural contribution to the change in the temperature of the maximum density of water with the addition of propan-2-01 El31 and the maximum in the ultrasonic absorption at x 2 ca. 0.18 [14], all suggest that additions of propan-2-01 to water, whilst maintaining water-rich conditions, induce the formation of structure in the solvent. The variation of the rate constants and the transition state parameters with solvent composition for the solvolysis of these complexes in water + propan-2-01 will be compared with similar variations in water + methanol [8] where the above indicators Ell-151 suggest that less structure is formed in water when methanol is added.…”

Positron Annihilation in and Adiabatic Compressibility of Ethylene Glycol Aqueous Solutions

“…clathrate-like) structures. In contrary, Baumgartner and Atkinson [9] relate the formation of such stuctures to the minima of the compressibility isotherms, while according to Andreae et al [10] the compressibility minimum can be explained in terms of solute-solvent complex formation.…”

Statistical Time Events in Enzymes: A Physical Assessmen

“…The equivalent circuit is shown in Figure 1, and expressions for the total capacity as a function of frequency are easily obtained in tenns of the sample and electrodes resistivity and capacity . 10 o It is also known 36 that the resistivity of the protein powder decreases exponentially with increasing hydration. 3 6 Using the above quoted expressions it can be shown that for this very reason the total capacity must increase abruptly at a critical value of the hydration.…”