émulsion

An emulsion is a mixture of two or more liquids that are normally immiscible, meaning they don't readily mix. Typically, one liquid is dispersed in the other in the form of tiny droplets. For example, oil and water are immiscible. An emulsion would be formed when small droplets of oil are suspended within water, or vice versa.

Emulsions require an emulsifying agent, also known as a surfactant, to stabilize them. Without an emulsifier, the dispersed droplets would quickly separate from the continuous phase. Emulsifiers work by having a hydrophilic (water-attracting) head and a lipophilic or hydrophobic (oil-attracting) tail. This dual nature allows them to sit at the interface between the oil and water droplets, reducing the interfacial tension and preventing the droplets from coalescing.

There are two main types of emulsions: oil-in-water (O/W) and water-in-oil (W/O). In an O/W emulsion, oil droplets are dispersed in a continuous water phase, such as milk. In a W/O emulsion, water droplets are dispersed in a continuous oil phase, like butter.

Emulsions are prevalent in everyday life and industry. They are found in food products like mayonnaise, salad dressings, and ice cream. They are also used in cosmetics, pharmaceuticals, paints, and agricultural sprays. The stability and properties of an emulsion depend on factors such as the type and concentration of the emulsifier, the size of the dispersed droplets, and the viscosity of the continuous phase.