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Macroemulsion
Macroemulsions are dispersed liquid-liquid, thermodynamically unstable systems with particle sizes ranging from 1 to 100 μm (orders of magnitude), which, most often, do not form spontaneously. Macroemulsions scatter light effectively and therefore appear milky, because their droplets are greater than a wavelength of light. They are part of a larger family of emulsions along with miniemulsions (or nanoemulsions). As with all emulsions, one phase serves as the dispersing agent. It is often called the continuous or outer phase. The remaining phase(s) are disperse or inner phase(s), because the liquid droplets are finely distributed amongst the larger continuous phase droplets. This type of emulsion is thermodynamically unstable, but can be stabilized for a period of time with applications of kinetic energy. Surfactants (as the main emulsifiers) are used to reduce the interfacial tension between the two phases, and induce macroemulsion stability for a useful amount of time. Emulsion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bancroft Rule
The Bancroft rule in colloidal chemistry states: "The phase in which an emulsifier is more soluble constitutes the continuous phase." This means that water-soluble surfactants tend to give oil-in-water emulsions and oil-soluble surfactants give water-in-oil emulsions. It is a general rule of thumb, still used, but regarded as inferior to HLD theory (Hydrophilic Lipophilic Difference), which takes many more factors into consideration. It was named after Wilder Dwight Bancroft, an American physical chemist, who proposed the rule in the 1910s. Technical details In all of the typical emulsions, there are tiny particles (discrete phase) suspended in a liquid (continuous phase). In an oil-in-water emulsion, oil is the discrete phase, while water is the continuous phase. What the Bancroft rule states is that contrary to common sense, what makes an emulsion oil-in-water or water-in-oil is not the relative percentages of oil or water, but which phase the emulsifier is more soluble in. So ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emulsions
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms ''colloid'' and ''emulsion'' are sometimes used interchangeably, ''emulsion'' should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include vinaigrettes, homogenized milk, liquid biomolecular condensates, and some cutting fluids for metal working. Two liquids can form different types of emulsions. As an example, oil and water can form, first, an oil-in-water emulsion, in which the oil is the dispersed phase, and water is the continuous phase. Second, they can form a water-in-oil emulsion, in which water is the dispersed phase and oil is the continuous phase. Multiple emulsions are al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adsorbtion
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a fluid (the ''absorbate'') is dissolved by or permeates a liquid or solid (the ''absorbent''). Adsorption is a ''surface phenomenon'', while absorption involves the whole volume of the material, although adsorption does often precede absorption. The term ''sorption'' encompasses both processes, while ''desorption'' is the reverse of it. Like surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent or metallic) of the constituent atoms of the material are fulfilled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of the bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potential Well
A potential well is the region surrounding a local minimum of potential energy. Energy captured in a potential well is unable to convert to another type of energy (kinetic energy in the case of a gravitational potential well) because it is captured in the local minimum of a potential well. Therefore, a body may not proceed to the global minimum of potential energy, as it would naturally tend to do due to entropy. Overview Energy may be released from a potential well if sufficient energy is added to the system such that the local maximum is surmounted. In quantum physics, potential energy may escape a potential well without added energy due to the probabilistic characteristics of quantum particles; in these cases a particle may be imagined to tunnel ''through'' the walls of a potential well. The graph of a 2D potential energy function is a potential energy surface that can be imagined as the Earth's surface in a landscape of hills and valleys. Then a potential well would be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hamaker Force Interactions
In molecular physics, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The van der Waals force quickly vanishes at longer distances between interacting molecules. Named after Dutch physicist Johannes Diderik van der Waals, the van der Waals force plays a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. It also underlies many properties of organic compounds and molecular solids, including their solubility in polar and non-polar media. If no other force is present, the distance between atoms at which the force becomes repulsive rather than attractive as the atoms approach one another is called the van der Waals contact distance; this phenomenon results ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DLVO Theory
The DLVO theory (named after Boris Derjaguin and Lev Landau, Evert Verwey and Theodoor Overbeek) explains the aggregation of aqueous dispersions quantitatively and describes the force between charged surfaces interacting through a liquid medium. It combines the effects of the van der Waals attraction and the electrostatic repulsion due to the so-called double layer of counterions. The electrostatic part of the DLVO interaction is computed in the mean field approximation in the limit of low surface potentials - that is when the potential energy of an elementary charge on the surface is much smaller than the thermal energy scale, k_ T. For two spheres of radius a each having a charge Z (expressed in units of the elementary charge) separated by a center-to-center distance r in a fluid of dielectric constant \epsilon_r containing a concentration n of monovalent ions, the electrostatic potential takes the form of a screened-Coulomb or Yukawa potential, : \beta U(r) = Z^2 \lambda_ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colloids
A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend the definition to include substances like aerosols and gels. The term colloidal suspension refers unambiguously to the overall mixture (although a narrower sense of the word '' suspension'' is distinguished from colloids by larger particle size). A colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension). The dispersed phase particles have a diameter of approximately 1 nanometre to 1 micrometre. Some colloids are translucent because of the Tyndall effect, which is the scattering of light by particles in the colloid. Other colloids may be opaque or have a slight color. Colloidal suspensions are the subject of interface and colloid science. This field of study was introduced in 1845 by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bulk Liquids
Bulk cargo is commodity cargo that is transported unpackaged in large quantities. Description Bulk cargo refers to material in either liquid or granular, particulate form, as a mass of relatively small solids, such as petroleum/crude oil, grain, coal, or gravel. This cargo is usually dropped or poured, with a spout or shovel bucket, into a bulk carrier ship's hold, railroad car/railway wagon, or tanker truck/ trailer/ semi-trailer body. Smaller quantities can be boxed (or drummed) and palletised; cargo packaged in this manner is referred to as breakbulk cargo. Bulk cargo is classified as liquid or dry. The Baltic Exchange is based in London and provides a range of indices benchmarking the cost of moving bulk commodities, dry and wet, along popular routes around the seas. Some of these indices are also used to settle Freight Futures, known as FFA's. The most famous of the Baltic indices is the Baltic Dry Indices, commonly called the BDI. This is a derived function ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffuse
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical potential. It is possible to diffuse "uphill" from a region of lower concentration to a region of higher concentration, like in spinodal decomposition. The concept of diffusion is widely used in many fields, including physics (particle diffusion), chemistry, biology, sociology, economics, and finance (diffusion of people, ideas, and price values). The central idea of diffusion, however, is common to all of these: a substance or collection undergoing diffusion spreads out from a point or location at which there is a higher concentration of that substance or collection. A gradient is the change in the value of a quantity, for example, concentration, pressure, or temperature with the change in another variable, usually distance. A change i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volume Fraction
In chemistry and fluid mechanics, the volume fraction φ''i'' is defined as the volume of a constituent ''V''''i'' divided by the volume of all constituents of the mixture ''V'' prior to mixing: :\phi_i = \frac Being dimensionless, its unit is 1; it is expressed as a number, e.g., 0.18. It is the same concept as volume percent (vol%) except that the latter is expressed with a denominator of 100, e.g., 18%. The volume fraction coincides with the volume concentration in ideal solutions where the volumes of the constituents are additive (the volume of the solution is equal to the sum of the volumes of its ingredients). The sum of all volume fractions of a mixture is equal to 1: :\sum_^ V_i = V ; \qquad \sum_^ \phi_i = 1 The volume fraction (percentage by volume, vol%) is one way of expressing the composition of a mixture with a dimensionless quantity; mass fraction (percentage by weight, wt%) and mole fraction (percentage by moles, mol%) are others. Volume concentration and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continuous Phase
A colloid is a mixture in which one substance consisting of microscopically dispersed Solubility, insoluble particles is suspension (chemistry), suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend the definition to include substances like aerosols and gels. The term colloidal suspension refers unambiguously to the overall mixture (although a narrower sense of the word ''suspension (chemistry), suspension'' is distinguished from colloids by larger particle size). A colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension). The dispersed phase particles have a diameter of approximately 1 nanometre to 1 micrometre. Some colloids are translucent because of the Tyndall effect, which is the scattering of light by particles in the colloid. Other colloids may be Opacity (optics), opaque or have a slight color. Colloidal suspensions are the subject of interfa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
