immiscibilis

Immiscibilis is a term used in chemistry to describe liquids that do not form a single homogeneous phase when combined. Derived from Latin immiscibilis, meaning not mixable, the term is applied to pairs of liquids that separate into distinct layers rather than dissolve into one another.

A common example is water and oil; these liquids are immiscible under ordinary conditions due to polarity differences and incompatible intermolecular interactions. Other typical immiscible pairs include water and hexane, water and many halogenated solvents, and most nonpolar organic solvents with water.

Causes: immiscibility arises when the enthalpy of mixing is unfavorable and the liquids differ in polarity and hydrogen bonding capability. In practice, the two liquids minimize contact with each other and form a clear interface; density differences determine which layer sits on top.

Consequences and uses: immiscible liquids exhibit phase separation, a principle exploited in liquid-liquid extraction, oil–water separation, and various industrial separations. Emulsions can temporarily stabilize immiscible mixtures with surfactants or agitation, but the two phases will tend to separate over time.

Partial or conditional immiscibility: some solvent pairs are only partially immiscible or become miscible at certain temperatures or in the presence of salts or co-solvents, illustrating the concept of a temperature-dependent miscibility gap.