Aggregative processes in aqueous solutions of isomeric 2-butoxyethanols at 298.15 K

Abstract

Ultrasound speed measurements across the entire composition range of aqueous mixtures of both isobutoxyethanol (iC 4 E 1 ) and tert-butoxyethanol (tC 4 E 1 ) have been made at 298.15 K with a sonic solution monitor that employs a '' pulse-echo-overlap '' technique. In addition, densities of aqueous mixtures of tC 4 E 1 were determined using a vibrating tube densimeter. These new data were complemented with literature values for densities of aqueous mixtures of tC 4 E 1 and for densities and sound speeds of aqueous mixtures of n-butoxyethanol (nC 4 E 1 ). In all cases, density values were converted to molar volumes, V m , and excess molar volumes, V m E . Estimates of the isentropic molar compression, K S,m [ ¼ À(@V m /@p) S ], and of its excess counterpart, K S,m E , were obtained from the combination of the ultrasound speeds and density values. Data reduction procedures were used to generate consistent sets of values for thermodynamic properties of isomeric amphiphiles with increasing degree of alkyl branching. The graphs for the composition dependence of excess partial molar volumes and isentropic compressions of water show enhanced visual impact. These graphs are used for presenting evidence for identifying the prevailing patterns of molecular aggregation. Segmentedcomposition models, including a version onto which a mass action component has been grafted, are employed, together with a simplified pseudo-phase model, to analyse the various excess molar quantities. The experimental evidence thus obtained is used to relate the effect of chain branching with the degree of self-aggregation of amphiphiles in aqueous solution. An unexpectedly low self-aggregation among iC 4 E 1 molecules is found and discussed in terms of vicinity to the lower critical solution temperature.

Excess Volumes, Densities, Speeds of Sound, and Viscosities for the Binary Systems of 1-Octanol with Hexadecane and Squalane at (298.15, 303.15 and 308.15) K

“…To achieve agreement with the other thermodynamic quantities, it is appropriate to shift from the volume-intensive κ S to the molar-intensive quantity K S,m [35,36],…”

Refractive Index of Liquid Mixtures: Theory and Experiment

“…Since the generalised-thermodynamic arguments [6c] leading to Equation (8) are also valid at non-zero angular frequencies, a fact corroborated by Buep's [6d] thermodynamic analysis of the complex permittivity of ideal liquid mixtures, the latter equation can be applied to e r (1) and hence to n 2 to give Equations (9) and (10)…”

“…The volumetric properties of aqueous mixtures of the former amphiphile have been studied [7] recently in our laboratory and those of the latter series have also been examined in detail. [8] The thermodynamic analysis of our refractive index data in conjunction with previously published density data [7] reveals two prominent features. Firstly, pear-shaped curves in plots of excess refractive indices against excess molar volumes exhibit three zones of different mutual change.…”

“…Therefore we ascribe the separation of isotherms noted in Figure 7 to less negative excess molar volumes brought out by increasing temperature that are translated into smaller excess refractive indices in the normal way. Amphiphiles dissolved in water are known to form molecular aggregates, [7,8,40] the nature of which varies with composition. According to this general behaviour, in the water-rich domain molecules of 1-PP-2-ol would aggregate into micelle-like small clusters, their hydrophilic groups establishing hydrogen bonds with the surrounding water molecules.…”

Composition measurements of crude oil and process water emulsions using thick-film ultrasonic transducers

“…The speed of sound itself was calculated from the time-offlight of the ultrasonic pulse, but corrected using the known data for distilled water (shown in Table 2) using the following formula [16]:…”