Liquid Mixtures (liquid + mixture)

Distribution by Scientific Domains

Kinds of Liquid Mixtures

  • binary liquid mixture

  • Selected Abstracts

    Integrated synthesis and extraction of short-chain fatty acid esters by supercritical carbon dioxide

    AICHE JOURNAL, Issue 4 2010
    Marta Lubary
    Abstract We developed an efficient, integrated reaction-extraction process for the production of short-chain fatty acid ethyl esters (FAEE) from milk fat, using carbon dioxide as the only processing solvent. FAEE were synthesized using a short-chain fatty acid selective lipase. The expansion of the liquid mixture of reactants by dense carbon dioxide enhanced the apparent lipase selectivity. In situ extraction of FAEE by a continuous flow of supercritical carbon dioxide proved to increase the lipase production rate. When the integrated process was operated with alternated periods of synthesis and product removal, the overall selectivity for short-chain FAEE increased as well, as a result of the combination of the selectivities of lipase and extraction solvent. A two-fold increase of the lipase productivity was achieved at these conditions, compared to a single batch reaction. The developed process enables the synthesis and isolation of high-value fatty acid derivatives from a natural source such as milk fat. 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

    A new methodology for the definition of odor zones in perfumery ternary diagrams

    AICHE JOURNAL, Issue 8 2006
    Vera G. Mata
    Abstract The new methodology called "Perfumery Ternary Diagram" helps perfumers in odor prediction, allowing a fast evaluation of the odor value in the headspace for all possible combinations of a non-ideal perfume liquid mixture with three fragrant components and one or more solvents. In this work, the determination of Perfumery Ternary Points (PTP) and Perfumery Binary Lines (PBL) is described, allowing a complete definition of Perfumery Ternary Diagram (PTD) odor zones, without the need to calculate a large number of points inside the triangle region. The methodology of PTP and PBL determination was applied to the system: limonene, geraniol, vanillin, and ethanol. The effect of solvent,ethanol,on the odor zones, namely on the number of PTP and on the shape of the PBL was studied, as well as the effect of the non-idealities. 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

    The effect of nanofibers on liquid,liquid coalescence filter performance

    AICHE JOURNAL, Issue 12 2005
    C. Shin
    Abstract A number of factors influence the efficiency and the economics of the separation of dispersed liquid drops in an immiscible liquid,liquid mixture. One important factor that controls the performance of a filter medium in the separation is the fiber size. Electrospun polymer nanofibers have diameters in the nanometer range and are arbitrarily long. The experimental results in this work show that adding nanofibers to conventional micron-sized fibrous filter media improves the separation efficiency of the filter media but also increases the pressure drop. An optimum in the performance occurs (significant increase in efficiency with minimal increase in pressure drop) with the addition of about 1.6% by mass of 250 nm diameter nylon 6 nanofibers to 5 micron diameter glass fibers in the filters. 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]

    UV curing kinetics and mechanism of a highly branched polycarbosilane

    Houbu Li
    Abstract The UV curing process in both air and nitrogen atmosphere for the highly branched polycarbosilane system was investigated by differential scanning photo calorimeter. The UV cured products were characterized by Fourier-transform infrared spectrometry (FTIR). By comparison with the FTIR results of the uncured liquid mixture and the cured samples, the possible cross-linking reactions were determined. The kinetics of the curing systems was studied. The rate constant k was calculated based on the experimental results. The activation energies in different curing conditions were obtained. According to these results, it was learned that the mechanism for the UV curing in nitrogen was controlled by the photolysis of photoinitiator. Comparably, the UV curing process in air was complicated. It was affected by not only the photolysis of photoinitiator, but also oxygen and tripropane glycol diacrylate. Copyright 2008 John Wiley & Sons, Ltd. [source]

    A Contactless Impedance Probe for Simple and Rapid Determination of the Ratio of Liquids with Different Permittivities in Binary Mixtures

    ELECTROANALYSIS, Issue 1 2009
    Franti, ek Opekar
    Abstract Simple contactless cells with planar or tubular electrodes have been designed for measurement of the permittivity of solutions. The cells, connected to an integrated circuit of astable multivibrator, respond primarily to the capacitance component of the cell impedance, the multivibrator frequency depends in a defined manner on the solution permittivity and is readily used as the analytical signal in determinations of the ratios of components in binary liquid mixtures; water solution of methanol, ethanol and dioxane have been tested. The response of the cell with planar electrodes satisfies well the simple theoretical model and both the cells provide results with a sufficient sensitivity, a low LOD value (units of %vol) and a good precision (around 1%rel). The cell simplicity, small dimensions, long-term stability and the possibility of powering them from a battery make them suitable for hand-held meters. As an example of application in practice, the content of ethanol was determined in the car fuel petrol. [source]

    An investigation of liquid film thickness during solutal Marangoni condensation using a laser absorption method: Absorption property and examination of measuring method

    Yoshio Utaka
    Abstract The objective of the study is to establish a method for measuring the thickness of thin condensates of liquid mixtures using a laser light absorption method during the process of water,ethanol Marangoni dropwise condensation. First, the extinction property of the test material, with unknown properties related to infrared laser light having a wavelength of 3.39m, was measured. Next, measurements were made of the variations in condensate film thickness after the sweeping of the heat transfer surface by departing drops in the Marangoni dropwise condensation cycle. The precision of this method was investigated on the basis of the extinction coefficient of the test material and the thickness of the liquid film. Results showed that this method provides good precision and is applicable to the measurement of other similar materials. 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 700,711, 2003; Published online in Wiley InterScience ( DOI 10.1002/htj.10124 [source]

    Excess Gibbs energy of binary liquid mixtures and the Wong,Sandler postulates

    AICHE JOURNAL, Issue 12 2004
    W. W. Focke
    First page of article [source]

    Excess thermodynamic properties in liquid binary mixtures

    F. Aliotta
    Abstract Excess volumes and adiabatic compressibility have been measured in several binary liquid mixtures to answer the question whether structural information can be gained through the analysis of the concentration dependence of the excess quantities. The obtained results are compared with independent indications from Raman spectroscopy, which is able to probe directly the occurrence and the nature of effective intermolecular interactions. Some doubts have arisen against the usual approach adopted for estimating the excess quantities and about the adequacy of the usual assumptions for the reference ideal behaviours. In particular, it is shown how excess compressibility can result just from statistical effects also in absence of any excess volume contribution. The leading idea is supported by the comparison of the experimental data with the results from a naive model for binary mixtures of hard spheres. The model turns out to be able to produce a very wide spectrum of structural and thermodynamic behaviours depending on the values of its parameters and on the nature (additive or non-additive) of the hard-sphere potential. A discussion is proposed on the re-evaluation of excess thermodynamic data and on their ability in providing direct information on intermolecular interactions. Copyright 2008 John Wiley & Sons, Ltd. [source]

    Raman spectroscopy and molecular simulation investigations of adsorption on the surface of single-walled carbon nanotubes and nanospheres

    Maher S. Amer
    Abstract Raman spectroscopy has, for long, been utilized to investigate material systems on the micro and mesoscales. Recently, the technique has proven its ability in exploring systems on the nanoscale. In this paper, we review our recent work on the Raman investigation of molecular adsorption from liquid mixtures on surfaces of single-walled carbon nanotubes and fullerene nanospheres, emphasizing the following major research findings: the development of a Raman-based technique capable of sensing local chemical interactions on the surface of carbon nanotubes and spheres; the molecular simulation results supporting the Raman investigation; the possibility of creating mesostructures based upon mixtures of carbon nanotubes and nanospheres that are crucial for selective adsorption. The current findings represent a major new thrust for the development of new nanostructured materials with superior adsorption capabilities and unique applications. Copyright 2007 John Wiley & Sons, Ltd. [source]

    EPR study of nitroxides formed from the reaction of nitric oxide with photolyzed amides

    Fan Wang
    Abstract Free radicals generated from UV irradiation of simple aliphatic amides in anaerobic and nitric oxide (NO)-saturated liquid mixtures or solutions gave EPR spectra of nitroxides. The application of isotopic effects to EPR spectra and the generation of radicals by transient radical attack on substrate molecules or by photolysing amine or acetoin were used to help identify photochemically produced radicals from the amides. The aliphatic amides used were formamide, acetamide and their N -methyl- or deuterium-substituted derivatives. Transient radicals used to attack the amides via hydrogen-atom abstraction were generated from the initiator AIBN or AAPH. The observation of various nitroxides indicates the reactivity of NO for trapping acyl, carbamoyl and other carbon-centered radicals. Possibly mechanistic pathways diagnosed with this trap are proposed. Copyright 2003 John Wiley & Sons, Ltd. [source]

    Characterization of Mixtures Part 1: Prediction of Infinite-Dilution Activity Coefficients Using Neural Network-Based QSPR Models

    MOLECULAR INFORMATICS, Issue 11-12 2008
    Subhash Ajmani
    Abstract The major problem in building QSAR/QSPR models for mixtures lies in their characterization. It has been shown that it is possible to construct QSPR models for the density of binary liquid mixtures using simple mole fraction weighted physicochemical descriptors. Such parameters are unsatisfactory; however, from the point of view of interpretation of the resultant models. In this paper, an alternative mechanism-based approach to the characterization of mixtures has been investigated. It has been shown that while it is not possible to build significant linear models using these descriptors, it has been possible to construct satisfactory artificial neural network models. The performance of these models and the importance of the individual descriptors are discussed. [source]

    Effect of water treatment on analyte and matrix ion yields in matrix-assisted time-of-flight secondary ion mass spectrometry: the case of insulin in and on hydroxycinnamic acid

    Wilfried Szymczak
    A systematic study was performed to identify the origin of surprisingly high analyte-to-matrix yield ratios recently observed in time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis of oligo- and polypeptides mixed in matrices of ,-cyano-4-hydroxycinnamic acid (4HCCA). Several sets of samples of porcine insulin in 4HCCA (1:3100 molar) were prepared from liquid solutions by a nebuliser technique, with more than one order of magnitude variation in sprayed material (substrate silicon). Following different periods of storage in air and/or vacuum as well as exposure to high-purity water, TOF-SIMS analysis was performed under oblique impact of 22 keV SF5+. Treatment with water involved either deposition of a droplet covering the whole sample for times between 1 and 20,min or spraying with water in droplet equivalent quantities. The analyte and matrix molecules were detected as protonated molecules (insulin also in doubly protonated form). Even the as-prepared samples usually showed insulin-to-4HCCA yield ratios exceeding the molar ratio of the mixed material. Upon ageing in vacuum the matrix ion yields remained constant but the analyte yields decreased, partly due to break-up of intrachain disulfide bonds. Water treatment resulted in a pronounced decrease in the 4HCCA yield, typically by a factor of five, in parallel with an increase of the insulin yield, by up to a factor of four. Evidence is provided that these changes occur concurrently with a partial dissolution of 4HCCA at the sample surface. The enhanced insulin yield was not correlated with the Na+ yield. The typically 20-fold increase in the insulin-to-4HCCA yield ratio, generated by water exposure of the samples, provides the explanation for the high yield ratios observed previously with water-treated samples. Spraying with water or repeated exposure to water droplets caused a pronounced degradation of the insulin parent yields in combination with an increasing appearance of signals due to the B- and A-chains of insulin. To clarify the issue of surface segregation, a few samples were prepared by spraying acetone-diluted solutions of insulin on previously deposited layers of 4HCCA. Whereas the insulin yields from as-prepared samples were rather low, the yields observed after water treatment were comparable with those observed with samples of insulin in 4HCCA. The results suggest that a large amount of insulin is present at the surface of samples prepared from liquid mixtures of insulin in 4HCCA. With both methods of sample preparation, however, high secondary ion yields of insulin were only obtained after exposure of the samples to water. The chemical changes responsible for this beneficial effect still need to be identified. Copyright 2002 John Wiley & Sons, Ltd. [source]