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Ouzo Effect
The ouzo effect (also louche effect and spontaneous emulsification) is a milky ('' louche'') oil-in-water emulsion that is formed when water is added to ouzo and other anise-flavored liqueurs and spirits, such as pastis, rakı, arak, sambuca and absinthe. Such emulsions occur with only minimal mixing and are highly stable. Observation and explanation The ouzo effect occurs when a strongly hydrophobic essential oil such as ''trans''-anethole is dissolved in a water-miscible solvent, such as ethanol, and the concentration of ethanol is lowered by addition of small amounts of water. Oil-in-water emulsions are not normally stable. Oil droplets coalesce until complete phase separation is achieved at macroscopic levels. Addition of a small amount of surfactant or the application of high shear rates (strong stirring) can stabilize the oil droplets. In a water-rich ouzo mixture the droplet coalescence is dramatically slowed without mechanical agitation, dispersing agents, or surfact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coalescence (chemistry)
In chemistry, coalescence is a process in which two phase domains of the same composition come together and form a larger phase domain. In other words, the process by which two or more separate masses of miscible Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration), forming a homogeneous mixture (a solution). The term is most often applied to liquids but also applies ... substances seem to "pull" each other together should they make the slightest contact. References External links IUPAC Gold Book Physical chemistry {{physical-chemistry-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louche Effect Grapefruit-cello
Louche () was a mobile animal-drawn agricultural seed drill invented by the Chinese agronomist Zhao Guo, a Han official in charge of agricultural production during the reign of Han Wudi in the Han dynasty (156 – 29 March 87 BC). According to the records of ''Political Commentator'' by the Eastern Han dynasty writer Cui Shi Cui Shi (崔湜; 671–713), courtesy name Chenglan (澄瀾), was a Chinese writer and politician. He served as an official of the Chinese Tang Dynasty and Wu Zetian's Zhou Dynasty, serving as a chancellor during the reigns of Wu Zetian's sons E ..., the Louche consisted of three feet and thus was called three-legged Lou. The three legs had three ditch diggers under it used for sowing. The Louche was animal powered and was pulled by an ox and the leg of the Louche directly dug a ditch in the flattened soil, sowed the seeds, covered the seeds, and pressed the land flat at the same time. The machine was known for its utility and efficiency for serving several ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phase Diagram
A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions (pressure, temperature, volume, etc.) at which thermodynamically distinct phases (such as solid, liquid or gaseous states) occur and coexist at equilibrium. Overview Common components of a phase diagram are ''lines of equilibrium'' or ''phase boundaries'', which refer to lines that mark conditions under which multiple phases can coexist at equilibrium. Phase transitions occur along lines of equilibrium. Metastable phases are not shown in phase diagrams as, despite their common occurrence, they are not equilibrium phases. Triple points are points on phase diagrams where lines of equilibrium intersect. Triple points mark conditions at which three different phases can coexist. For example, the water phase diagram has a triple point corresponding to the single temperature and pressure at which solid, liquid, and gaseous water can coexist in a stabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinodal
In thermodynamics, the limit of local stability with respect to small fluctuations is clearly defined by the condition that the second derivative of Gibbs free energy is zero. : 0 The locus of these points (the inflection point within a G-x or G-c curve, Gibbs free energy as a function of composition) is known as the spinodal curve.G. Astarita: ''Thermodynamics: An Advanced Textbook for Chemical Engineers'' (Springer 1990), chaps 4, 8, 9, 12.Sandler S. I., ''Chemical and Engineering Thermodynamics''. 1999 John Wiley & Sons, Inc., p 571.Koningsveld K., Stockmayer W. H., Nies, E., ''Polymer Phase Diagrams: A Textbook''. 2001 Oxford, p 12. For compositions within this curve, infinitesimally small fluctuations in composition and density will lead to phase separation via spinodal decomposition. Outside of the curve, the solution will be at least metastable with respect to fluctuations. In other words, outside the spinodal curve some careful process may obtain a single phase system. Insi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ostwald Ripening
Ostwald ripening is a phenomenon observed in solid solutions or liquid sols that describes the change of an inhomogeneous structure over time, i.e., small crystals or sol particles dissolve, and redeposit onto larger crystals or sol particles. Dissolution of small crystals or sol particles and the redeposition of the dissolved species on the surfaces of larger crystals or sol particles was first described by Wilhelm Ostwald in 1896. For colloidal systems, Ostwald ripening is also found in water-in-oil emulsions, while flocculation is found in oil-in-water emulsions. Mechanism This thermodynamically-driven spontaneous process occurs because larger particles are more energetically favored than smaller particles. This stems from the fact that molecules on the surface of a particle are energetically less stable than the ones in the interior. Consider a cubic crystal of atoms: all the atoms inside are bonded to 6 neighbours and are quite stable, but atoms on the surface are onl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Light Scattering
Dynamic light scattering (DLS) is a technique in physics that can be used to determine the size distribution profile of small particles in suspension or polymers in solution. In the scope of DLS, temporal fluctuations are usually analyzed using the intensity or photon auto-correlation function (also known as photon correlation spectroscopy or quasi-elastic light scattering). In the time domain analysis, the autocorrelation function (ACF) usually decays starting from zero delay time, and faster dynamics due to smaller particles lead to faster decorrelation of scattered intensity trace. It has been shown that the intensity ACF is the Fourier transform of the power spectrum, and therefore the DLS measurements can be equally well performed in the spectral domain. DLS can also be used to probe the behavior of complex fluids such as concentrated polymer solutions. Setup A monochromatic light source, usually a laser, is shot through a polarizer and into a sample. The scattered light then ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micron
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Units (SI) equalling (SI standard prefix "micro-" = ); that is, one millionth of a metre (or one thousandth of a millimetre, , or about ). The nearest smaller common SI unit is the nanometre, equivalent to one thousandth of a micrometre, one millionth of a millimetre or one billionth of a metre (). The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria, and for grading wool by the diameter of the fibres. The width of a single human hair ranges from approximately 20 to . The longest human chromosome, chromosome 1, is approximately in length. Examples Between 1 μm and 10 μm: * 1–10 μm – length of a typical bacterium * 3–8 μm – width of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Small-angle Neutron Scattering
Small-angle neutron scattering (SANS) is an experimental technique that uses elastic neutron scattering at small scattering angles to investigate the structure of various substances at a mesoscopic scale of about 1–100 nm. Small angle neutron scattering is in many respects very similar to small-angle X-ray scattering (SAXS); both techniques are jointly referred to as small-angle scattering (SAS). Advantages of SANS over SAXS are its sensitivity to light elements, the possibility of isotope labelling, and the strong scattering by magnetic moments. Technique During a SANS experiment a beam of neutrons is directed at a sample, which can be an aqueous solution, a solid, a powder, or a crystal. The neutrons are elastically scattered by nuclear interaction with the nuclei or interaction with magnetic momentum of unpaired electrons. In X-ray scattering, photons interact with the electronic cloud so the bigger the element, the bigger the effect is. In neutron scattering, neutron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Chemical Society
The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 155,000 members at all degree levels and in all fields of chemistry, chemical engineering, and related fields. It is one of the world's largest scientific societies by membership. The ACS is a 501(c) organization, 501(c)(3) non-profit organization and holds a congressional charter under Title 36 of the United States Code. Its headquarters are located in Washington, D.C., and it has a large concentration of staff in Columbus, Ohio. The ACS is a leading source of scientific information through its peer-reviewed scientific journals, national conferences, and the Chemical Abstracts Service. Its publications division produces over 60 Scientific journal, scholarly journals including the prestigious ''Journal of the American Chemical Society'', as well as the weekly tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleation
In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears. For example, if a volume of water is cooled (at atmospheric pressure) below 0°C, it will tend to freeze into ice, but volumes of water cooled only a few degrees below 0°C often stay completely free of ice for long periods (supercooling). At these conditions, nucleation of ice is either slow or does not occur at all. However, at lower temperatures nucleation is fast, and ice crystals appear after little or no delay. Nucleation is a common mechanism which generates first-order phase transitions, and it is the start of the process of forming a new thermodynamic phase. In contrast, new phases at continuous phase transitions start to form immedi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dispersion (materials Science)
In materials science, dispersion is the fraction of atoms of a material exposed to the surface. In general: :''D'' = ''N''S/''N''T where ''D'' is the dispersion, ''N''S is the number of surface atoms and ''N''T is the total number of atoms of the material. Dispersion is an important concept in heterogeneous catalysis, since only atoms that are exposed to the surface are able to play a role in catalytic surface reactions. Dispersion increases with decreasing crystallite size and approaches unity at a crystallite diameter of about 0.1 nm. Related article Emulsion dispersion An emulsion dispersion is thermoplastics or elastomers suspended in a liquid state by means of emulsifiers. Preparation Emulsions are thermodynamically unstable liquid/liquid dispersions that are stabilized. Emulsion dispersion is not about reac ... References Materials science {{Materials-sci-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
