أكتوبر 14th, 2018

 

Aerosol

A suspension of small particles in a gas. The particles may be solid or liquid or a mixture of both. Aerosols are formed by the conversion of gases to particles, the disintegration of liquids or solids, or the resuspension of powdered material. Aerosol formation from a gas results in much finer particles than disintegration processes ( except when condensation takes place directly on existing large particles). Dust, smoke,…

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Adsorption

A process in which atoms or molecules move from a bulk phase (that is, solid, liquid, or gas) onto a solid or liquid surface. An example is purification by adsorption where impurities are filtered from liquids or gases by their adsorption onto the surface of a high-surface-area solid such as activated charcoal. Other examples include the segregation of surfactant molecules to the surface of a liquid, the bonding…

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adhesive

A material capable of fastening two other materials together by means of surface attachment. The terms glue, mucilage, mastic, and cement are synonymous with adhesive. In a generic sense, the word adhesive implies any material capable of fastening by surface attachment, and thus will include inorganic materials such as

portland cement and solders. In a practical sense, however, adhesive implies the broad set of materials composed of organic…

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acylation

A process in which a hydrogen atom in an organic compound is re­placed by an acyl group (R-CO, where R = an organic group). The reaction in­volves substitution by a nucleophile (electron donor) at the electrophilic carbonyl group (C=O) of a carboxylic acid derivative. The substitution usually proceeds by an addition-elimination sequence. Two common reagents, with the general formula RCOX, that bring about acylation are acid halides…

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