It explains plainly.
Intertek provides detailed characterisation of surface active agents (surfactants). A surface active agent, or surfactant, is a substance which lowers the surface tension of the medium in which it is dissolved, the interfacial tension with other phases, and is positively adsorbed at the liquid-vapour interface and other interfaces. Surfactant lower the surface tension of a liquid by spreading spontaneously over its surface.
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