Surfactant Surfactant Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants. The term "surfactant" is a blend of "surface active agent". In the United States National Library of Medicine's Medical Subject Headings (MeSH) vocabulary, "surfactant" is reserved for the meaning pulmonary surfactant. For the more general meaning, "surface active agent/s" is the heading. Surfactants are usually organic compounds that are amphiphilic, meaning they contain both hydrophobic groups (their "tails") and hydrophilic
Surface tension known as equilibrium. The horizontal component of is canceled by the adhesive force, . The more telling balance of forces, though, is in the vertical direction. The vertical component of must exactly cancel the difference of the forces along the solid surface, . Since the forces are in direct proportion to their respective surface tensions, we also have: where This means that although the difference between the liquid–solid and solid–air surface tension, , is difficult to measure directly, it can be inferred from the liquid–air surface tension, , and the equilibrium contact angle, , which is a function of the