Phase behaviours and conductivity study of water/CPC/alkan-1-ol (C4 and C5)/1-hexane water/oil microemulsions with reference to their structure and related thermodynamics

The microemulsion forming systems of water/cetylpyridinium chloride/butan-1-ol/n-hexane, and water/cetylpyridinium chloride/pentan-1-ol/n-hexane have been studied with respect to their phase behaviours and percolation of conductance to derive information on their droplet physicochemical characteristics (dimension, interfacial area and composition, and number density). This was carried out at different water contents at specific ratios of surfactant and cosurfactant and at various temperatures. From the information collected, the energetics of the transfer of the alkanol (butan-1-ol and pentan-1-ol) from the continuous oil-phase to the interfacial region (the interphase) have been estimated. At the conductance percolation threshold, the droplets cluster or associate, can be considered to form a pseudophase similar to surfactants forming micelles. Based on this concept, the energetics of the clustering process have been evaluated, and the results are discussed in comparison with other recently studied systems.Key words: energetics of clustering, percolation, phase diagrams, microemulsions and thermodynamics of transfer.

Thermodynamics of Transfer and Solvatochromism of 1,5-Diaryl-3-Nitroformazans in 1,4-Dioxane–Water Mixtures

The ionization constants of 1,5-diaryl-3-nitroformazans in 20–80%(

Modeling of transfer properties using revised HKF theory: thermodynamics of transfer of an amino acid and small peptides from water to urea–water solutions at 298.15 K

Relative densities, [Formula: see text] and heat capacity ratios, [Formula: see text] have been measured for aqueous solutions of glycine, glycylglycine, and glycylglycylglycine in aqueous urea solutions containing 1–13 mol kg−1 urea. These data have been used to calculate apparent molar volumes, [Formula: see text] and apparent molar heat capacities, [Formula: see text] which in turn have been used to obtain standard state volumes, [Formula: see text] and standard state heat capacities, [Formula: see text].Volumes and heat capacities of transfer from water to urea have been calculated from our reported standard state data. Heat capacities of transfer of the investigated systems have been modeled using a procedure developed from the semiempirical calculation procedures proposed by Helgeson, Kirkham, and Flowers. Keywords: amino acids, peptides, calorimetry, transfer thermodynamics, HKF theory.