Phase investigations of fats. II. Systems containing oleic and stearic acids and an organic solvent

1. The ternary systems oleic acid-stearic acid-commercial hexane and oleic acid-stearic acid-acetone containing varying amounts of the three components have been equilibrated at 0°C., −10°C., −20°C., −30°C., and −40°C.
2. From compositional data of the liquid and solid phases in equilibrium at each isotherm, ternary phase diagrams have been constructed. From these diagrams it is possible to predict the degree of separation which can be obtained with any given mixture of oleic and stearic acids, using either acetone or commercial hexane as solvent.
3. With practical solvent ratios the phase diagrams at −20°C., −30°C., and −40°C., exhibit closed areas representing liquid phase composition. The liquid phase boundaries have been established for each isotherm investigated.
4. The intersolubilizing effect of oleic acid on stearic acid, greater in commercial hexane than in acetone, and the possible formation of mixed crystals of oleic and stearic acid have been noted.
5. Oleic acid of high purity can be obtained as one of the practical applications of these data.

     

Bioremediation of polycyclic aromatic hydrocarbons: current knowledge and future directions

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds that have accumulated in the natural environment mainly as a result of anthropogenic activities such as the combustion of fossil fuels. Interest has surrounded the occurrence and distribution of PAHs for many decades due to their potentially harmful effects to human health. This concern has prompted researchers to address ways to detoxify/remove these organic compounds from the natural environment. Bioremediation is one approach that has been used to remediate contaminated land and waters, and promotes the natural attenuation of the contaminants using the in situ microbial community of the site. This review discusses the variety of fungi and bacteria that are capable of these transformations, describes the major aerobic and anaerobic breakdown pathways, and highlights some of the bioremediation technologies that are currently available. Copyright © 2005 Society of Chemical Industry     

Optical constants in the IR from thin film interference and reflectance: the reststrahlen region of muscovite mica

A new technique for determining the IR optical constants of materials that can be formed into thin films is presented. At a given wavelength the thickness of the film t, the index of refraction n, and the extinction coefficient k combine to produce interference effects in the film, which in turn control reflectance from the film. When reflectance is plotted vs thickness the resultant curve is a unique function of n and k. Values of n and k are determined by curve fitting. The technique is illustrated using thin films of muscovite mica, and values of n and k are reported for wave numbers from 1200 to 400 cm-1, which include the reststrahlen region of mica.     

Molecular distillation of a hydrogenated cottonseed oil and certain characteristics of the distilled fractions

Summary 1. A hydrogenated cottonseed oil has been molecularly distilled, and the distilled fractions examined. 2. Fractionation of a molecularly distilled oil occurs, as is to be expected, on the basis of variations in molecular weight of the glycerides. The composition of cottonseed oil is such that there is a considerable separation of the glycerides according to their degree of unsaturation. The composition of peanut oil is such that similar separation can only be slight. Soybean oil is in this respect intermediate between cottonseed oil and peanut oil. 3. Molecular distillation of hydrogenated cottonseed oil causes a segregation of tocopherols and related compounds similar to that observed in peanut oil. However, the fractions first distilled from the oil are relatively weak in antioxygenic properties. It appears probable that their lack of effectiveness is due to the presence of unknown substances capable of inhibiting or counteracting the action of tocopherols. However, the presence of substances other than tocopherols, which respond to or interfere with the Emmerie-Engel test is not to be excluded. The tocopherols in the potent fractions are more effective thana-tocopherol, but less effective than γ-tocopherol. This is one of four regional research laboratories operated by the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Dilatometric investigations of fats

Summary 1. Dilatometric curves have been determined over the complete melting range for samples of prime steam lard, oleo oil, all-hydrogenated vegetable shortening, and partially hydrogenated cottonseed oil. From the dilatometric data estimates have been made of the percentages of solids and liquid in the fats at different temperatures. 2. Estimates of the percentages of solids and liquid in the hydrogenated cottonseed oil agreed with those previously reported on the same oil from calorimetric data when allowance was made for a lack of equilibrium conditions in the calorimetric experiment. Since a condition of equilibrium between solids and liquid is attained in the dilatometer, this instrument is to be preferred to the calorimeter for determining the composition of fats in terms of the two phases. 3. The consistency of the fats, as measured by micropenetrations, was different for different fats which contained equal percentages of solids. The consistency, therefore, is not determined solely by the amount of solids present, but also by the character of the solid particles. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Metal contamination of urban soils in the vicinity of a municipal waste incinerator: one source among many

Concern from local residents about possible contamination with metals and PCDD/F (dioxins and furans) from fugitive and stack emissions from the Byker municipal solid waste incinerator in Newcastle upon Tyne led the City Council to initiate a study of the concentration of these pollutants in soils. We report here the results for the metals and arsenic. Soils were sampled at distances up to 2.25 km from the incinerator stack. The intensity of sampling in concentric zones was four times greater in the northeast (down-wind) direction, and twice as great in the northwest and southeast directions, compared to the southwest (up-wind) direction. In total 163 samples were collected and analyzed for total As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Concentrations were generally elevated above background levels, but were typical of those found in other urban areas. For As, Cd, Cu, Hg, Pb, and Zn, contamination hotspots were identified. These were spread throughout the sampling area, and there was no evidence of greater concentrations down-wind of the incinerator compared to other directions, nor of any trend in concentration at increasing distance from the incinerator. We concluded that metal contamination resulting from the incinerator could not be detected in an environment with generally elevated concentrations. Potential sources for many of the hotspots of contamination were identified in a survey of historic land use based on maps of the locality dating back to 1856. Detailed investigations of particular areas with serious contamination will now be undertaken by the local authorities using the CLEA (Contaminated Land Exposure Assessment) model.     

Two-dimensional metallic photonic band-gap crystals fabricated by LIGA

 Two-dimensional metallic photonic band-gap crystals, consisting of square and triangular lattices of nickel pillars, were fabricated by the LIGA process. In particular, PMMA slabs with a thickness of up to 800 μm were irradiated with synchrotron radiation and the holes produced were then filled with nickel via electroforming. The lattice constant, i.e., the center-to-center distance between the pillars, is either 60 μm or 40 μm for the square and triangular structures respectively. The metal filling ratio is 10% for the square and 20% for the triangular structures. Transmission and reflection measurements demonstrate that the metallic photonic band-gap crystals show a cutoff frequency in the far infrared regime between 2 and 5 THz. It is concluded that LIGA is a promising method for the fabrication of 2-D metallic photonic band-gap structures, which could be potentially used as passive filters in THz devices. Received: 10 August 2001/Accepted: 24 September 2001