This paper is an attempt to summarise comparative aspects like definition, theories, types, methods of preparations, advantages, disadvantages and methods of analysis of emulsion, microemulsion and nanoemulsion. Ipp240b heterogeneous dispersions emulsions microemulsion 2 emulsion an emulsion is a dispersion in which the dispersed phase is composed of small. It possess internal forces that tend to promote association of the molecules to resist distortion of the sphere. In an emulsion, one liquid contains a dispersion of the other liquid. The oriented wedge theory of emulsions and the inversion of. The strategy was put forth in a discovery institute manifesto known as the wedge document. Oriented wedge theory this theory assumes monomolecular layers of emulsifying agent curved around a droplet of the internal phase of the emulsion depending on the solubility of these agents in that particular liquid. This theory requires that to achieve maximum interfacial density of emulsifier, thus producing the maximum decrease in free energy and the maximum increase in strength of interfacial film the end of a surfactant emulsifier molecule, which has the greater crosssectional area, should be oriented toward the. Full text full text is available as a scanned copy of the original print version.
Reasons for instability can be understood from the nature of immiscible. Of the typical soluble emulsifying agents sodium oleate may be cited as an example. Diy brick rocket stove cooking without electrical power duration. Annotations are viewable on desktop computers or desktop site of mobile devices. This theory for the manner in which emulsions are stabilized has been developed from the work of langmuir and of harkins. Doc types of emulsifying agents rehan ashraf academia. Harkins proposed an oriented wedge theory of emulsions. All liquids have tendency to assume a shape having the minimal surface area exposed. The oriented wedge theory of emulsions created date. The wedge strategy is a creationist political and social action plan authored by the discovery institute, the hub of the pseudoscientific intelligent design movement. Because emulsifying agents have hydrophilic portion and hydrophobic portion, they orient themselves according to solubility. Theories of emulsions monomolecular adsorption theory oriented wedge theory oriented adsorption theory plastic or interfacial.
Orientedwedge theory this theory assumes monomolecular layers of emulsifying agent curved around a droplet of the internal phase of the emulsion depending on the solubility of these agents in that particular liquid. The oriented wedge theory of emulsions pdf free download. Ppt emulsions powerpoint presentation free to download. Emulsion is a type of liquid dosage form for pharmaceutical use. What is harkins oriented wedge theory according to the oriented wedge theory, the difference in the relative size of the polar and nonpolar groups of the surfactant explains the type of the formed emulsion. Thetheory of molecular orientation in surfaces is thus of primeimpor. Articles from proceedings of the national academy of sciences of the united states of america are provided here courtesy of national academy of sciences.
An emulsion is usually a mixture of two products such as oil and water that do not mix together or. At positive spontaneous curvatures, ow emulsions are stable. The liquid droplets the disperse phase are dispersed in a liquid medium the continuous phase. This paper is an attempt to summarise comparative aspects like definition, theories, types, methods of preparations, advantages, disadvantages and methods of analysis of emulsion. According t o this theory the oillike or non polar ends of.
Get a printable copy pdf file of the complete article 696k, or click on a page image below to browse page by page. That different stabilizers led to preferential curvature of the oilwater interface was first suggested under the title of the oriented wedge theory5. The oriented wedge theory of emulsions indicates thatif thenonpolarendofthemoleculeof theemulsifying agent is the smaller, the emulsion will be one of oil in wateror of the ordinary typewhile if the polar endis the smaller, the droplets will be of water. Proceedings of the national academy of sciences of the united states of america, volume 11, issue 10, 1925, pp. Double emulsions may be either of the waterinoilinwater type wow with dispersed oil globules containing smaller aqueous droplets or of the oilinwaterin oil type owo with dispersed aqueous globules containing smaller oily dispersed droplets. One notable component of the work was its desire to address perceived social consequences and to promote a social conservative agenda on a wide range of issues including abortion, euthanasia, sexuality, and. Live simple, live free tinyhouse prepper recommended for you. Pdf preparation of stable direct emulsions stabilized with.
The correspondence between the equilibrium phase behavior of oilwater. Disrupt the oriented structure of the emulsifiers interfacial phase with. This based on the presumption that certain emulsifying agents orient themselves about and within a liquid in a manner reflective of their solubility in that particular liquid. It is based upon the concept that the molecules of the emulsifier orient themselves in the interface between the dispersed and continuous phases, forming a wedge, the curvature of which determines the.
The oriented wedge theory of emulsions and the inversion of emulsions. A simple geometric theory for the stabilization of emulsions is that of the oriented wedge, in which the adsorbed surfactant molecules are assumed to form a uniform structure of wedges around the emulsion droplet. Orientedwedgetheory concept this theory deals with formation of monomolecular layers of emulsifying agent curved around a droplet of the. Pharmaceutical applications of emulsions widened especially after micro and nanoemulsion emergence.
The oriented wedge theory of emulsions and the inversion of emulsions1 for the formation of an emulsion the presence of an emulsifying agent is essential, except in the case in which the emulsion is very dilute. Emulsification is not a spontaneous process and hence emulsions have minimal stability. Theory oriented wedge theory interfacial film theory. The oriented wedge theory revisited american chemical society. Both the phase behavior and emulsion stability are argued to be dependent on the bending elasticity of the surfactant monolayer at the oil. This theory deals with formation of monomolecular layers of emulsifying agent curved around a droplet of the internal phase of the emulsion.
The stability of emulsions, monomolecular and polymolecular films, thickness of the water film on salt solutions, and the spreading of liquids. Phase can be easily flavored to isolate the unpleasant taste of the dispersed phase from the tongue. Wo emulsions are generally formed if the aqueous phase constitutes oriented wedge theory of emulsions and the inversion of emulsions. A simple geometric theory for the stabilization of. Common examples of emulsions include egg yolk, butter, and mayonnaise. Emulsions free download as powerpoint presentation. A film of emulsifying agent prevents the contact and coslescing of the dispersed phase. This theory requires that to achieve maximum interfacial. The oriented wedge theory of emulsions and the inversion. This stated that for soaps such as the monovalent soaps for which the crosssection of the metal ion is smaller than the paraffin chain, the emulsion would be of the oilinwater type so as to form an interfacial film of the greatest density, and vice versa. Emulsifying agent anti oxidants antimicrobial preservative. Aug 20, 2018 theories of emulsions monomolecular adsorption theory oriented wedge theory oriented adsorption theory plastic or interfacial.
An emulsion is a type of colloid formed by combining two liquids that normally dont mix. The preparation of emulsions requires energy to disperse the organic phase solvent or solution in water. The wedge strategy was designed with both fiveyear and twentyyear goals in mind in order to achieve the conversion of the mainstream. In a system containing two immicible liquids, emulsifying agents would be preferentially soluble in one. The group with the larger cross sectional area will be oriented outside of the droplet. Preparation of stable direct emulsions stabilized with a system of phospholipid emulsifiers. The oriented wedge theory of emulsions indicates that if the nonpolar end of the molecule of theemulsifying agent is the smaller, the emulsion will be one of oil in wateror of the ordinary typewhile if the polar end is the smaller, the droplets will be of water. Emulsion formation, stability, and rheology tharwat f. An emulsion is a stable dispersion of two or more immiscible liquids held in. Preparation of stable direct emulsions stabilized with a. This assumes mono molecular layers of emulsifying agent curved around a droplet of the internal phase of the emulsion.
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