Whats in your Soap?

Paige Stark

Surfactants in Soaps

In chemistry, soap is a salt of a fatty acid. Consumers mainly use soaps as surfactants for washing, bathing, and cleaning. But what are surfactants? They are compounds that lower the surface tension between two liquids or between a liquid and a solid. Surfactants also act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.

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Surfactant Structures & Compounds

Surfactants are organic compounds that are amphiphilic, meaning they contain both hydrophobic groups (their tails) and hydrophilic groups (their heads). Therefore, a surfactant contains both a water-insoluble (or oil-soluble) component and a water-soluble component. Surfactants will diffuse in water and absorb at interfaces between air and water or at the interface between oil and water, in the case where water is mixed with oil. The water-insoluble tail group may extend out of the bulk water phase, into the air or into the oil phase, while the water-soluble head group remains in the water phase.

World production of surfactants is estimated at 15 Mton/y, of which about half are soaps. Other surfactants produced on a particularly large scale are linear alkybenzensesulfonates (1700 kton/y), lignin sulfonates (600 kton/y), fatty alcohol ethoxylates (700 ktons/y), and alkylphenolethoxylates (500 kton/y).