Raman scattering and water structure in nonionic amphiphile solutions.
The structure of water in aqueous solutions of polyoxyethylene nonionic amphiphiles ${\mathrm{C}}_{10}$${\mathrm{E}}_{5}$, where ${\mathrm{E}}_{5}$ denotes ${\mathrm{H}}_{21}$(${\mathrm{OCH}}_{2}$${\mathrm{CH}}_{2}$${)}_{5}$OH, is studied by Raman scattering along an isothermal path crossing the isotropic one-phase region from 0 to 1 amphiphile volume fraction \ensuremath{\varphi}. The isotropic OH stretching-vibration spectrum points out a water behavior that depends on the amphiphile concentration. The data analysis is performed using the bond-percolation model developed for water. The interpretation of scattering data leads to the following structural picture for the water in the systems: for \ensuremath{\varphi} lower than 0.75, water is partially bound to the oxyethylene groups of the amphiphile; above \ensuremath{\varphi}=0.75 all water present in the system is bound. Analogously to the behavior of water in confined geometries, the structure of bound water presents a local fourfold-coordinated environment.
Water compressibility in confined spaces
In order to explore the compressibility of water sequestered in droplets surrounded by surfactant molecular films (reverse micelles), we custom-built a high-precision velocimeter. The apparatus comprises two ultrasonic small-sized cells, electronic generators and a computer-controlled digital scope. We carried out a systematic study of the stability and reproducibility of the experimental set-up which yields an accuracy of 10/sup -5/. The ultrasound velocity, the apparent volume, and compressibility of encapsulated water were determined in charged and uncharged molecular films as a function of water concentration. We observed a close relationship between the measured parameters of encapsulated water, the chemical nature of the surfactant molecular film and the number of water molecules in interaction. The values obtained are higher than that reported for bulk water and are assigned to the surfactant-water interactions arising between the head groups and water molecules.
Organic constituents in process water from the in-situ retorting of oil from oil-shale kerogen
Capillary-column gas-chromatography/mass-spectrometry (GC/MS) was performed on the acid, base, and neutral fractions o'f liquid- and particulate-phase methylene chloride extracts of a composite sample of raw process water collected from separator Tank 6 by the Laramie Energy Technology Center. Of. the 160 extractable and chromatographable organic comP.ounds tentatively :identified, the following compou~d classes were found· (listed in decreasing order of. abundance):