Measurement of permittivity of aqueous solutions at 44 GHz by FM receiver

An instrument using a variable-thickness waveguide cell has been developed for measurement of absolute complex permittivity at 44 GHz. The superheterodyne is used to rise the sensitivity. The results of measurements of water and saccharose aqueous solutions in the range of 15–27 °C are presented.     

Coagulation of poly(p-phenylene benzobisoxazole) in polyphosphoric acid using aqueous and nonaqueous solutions

Diffusion of aqueous and nonaqueous coagulants into lyotropic/nematic solutions of poly(phenylene benzobisoxazole) in polyphosphoric acid using fluorescence microscopy is reported. The fluorescence microscopy technique offers advantages in that the experiment is independent of the coagulant and the experiments can be performed in a front surface mode so that optically thin samples are not required. The diffusion process is modeled as Case II diffusion as described by Crank and Park. The apparent diffusion coefficients are found to range from ～ 2 × 10^?6 cm²/s to ～ 2 × 10^?7 cm²/s for aqueous and nonaqueous coagulants. The apparent diffusion coefficients can be varied by several orders of magnitude (e.g., down to ～ 3 × 10^?10 cm²/s) by varying the concentration of polyphosphoric acid in the coagulant. © 1995 John Wiley & Sons, Inc.     

Thermodynamics of association for benzene-benzyl alcohol,benzene-phenethyl alcohol,and fluorobenzene-benzyl alcohol in dilute aqueous solution

Vapor pressure measurements have been made on dilute aqueous solutions of benzene-benzyl alcohol (BZOH), benzene-phenethyl alcohol (PEOH), and fluorobenzene-BZOH at 15, 25, 35, and 45°C. The benzene results have been interpreted with a mass action model which attributes deviations from ideality to the formation of benzene dimers and heterodimers with BZOH and PEOH. The benzene heterodimers form endothermically at 25°C with large and negative heat capacity changes. The dimerization constant for the benzene-BZOH dimer reaches a maximum of 0.57 M^–1 at about 37°C, while the benzene-PEOH dimer reaches a maximum of 0.60 M^–1 around 30°C. The fluorobenzene results have been interpreted with a mass action model which, in addition to fluorobenzene dimers and heterodimers, includes the formation of a fluorobenzene-BZOH trimer. Thermodynamic properties for these aggregates are reported and compared with results obtained in previous studies.     

Photocurrent characteristics in Cu2O/Pt and Cu2O/TiO2 photoelectrochemical cells in aqueous and non-aqueous electrolytes

Photocurrent characteristics of the Cu₂O/Pt and Cu₂O/TiO₂ photoelectro-chemical cells have been presented. In aqueous solution, a slow deterioration of power output occurs approximately at the rate of 50% per day. Operation in non-aqueous solutions (acetonitrile and ethanol) also produced a deterioration of power output. However in ethanol, it was found that the deterioration reversed itself and a new cycle of deterioration and rejuvenation began. These suggest that the deterioration is not due to a chemical reduction process at the electrode surface but other factors such as migration of charged defect centres in the depletion layer or chemical reaction on the electrode surface.     

Ionic radii in aqueous solutions

The aqueous ionic radii of 35 ions have been calculated from published data of the average distances between the ions and the nearest water molecules, obtained by diffraction and computer simulation methods.     

Partitioning of alkali halides in aqueous dextran-ficoll two-phase system

Partitioning of alkali halides MeX in aqueous dextran-Ficoll two-phase system of fixed polymer and ionic composition was studied. It is found that NaCl and LiX concentrate in the Ficoll-rich phase, while all KX, RbX, and CsX concentrate in the dextran-rich phase. Partitioning of KX, RbX, and CsX in the presence of a large excess of NaCl is found to depend on the type of the halide anion X^–.     

Simultaneous detection of total and halogenated hydrocarbons in complex environmental samples

A state-of-the-art gas chromatographic system for automatic simultaneous detection of halogenated and normal hydrocarbons has been developed, which consists of a standard Hewlett-Packard 5880 with a fused silica capillary column, whose effluent is split between the standard flame ionization detector and a Tracor Hall electroconductivity detector. The system provedes excellent capillary chromatography results and high sensitivity for halogenated compounds (a detection limit of 1 ppm Archlor 1254 in fuel oil). Reliability has been provides in the daily analysis of complex environmental samples. Emergency response cleanup and the containment of hazardous chemical spills and chemical dump sites forces one to deal with samples that are very complex. The contain large numbers of naturally occurring organic compounds and varying types of organic pollutants. Capillary chromatographic techniques of gas chromatographic and gas chromatographic/mass spectrometric analyses are necessary to achieve the resolution required for the analysis of these samples.