In the context of emulsions, what is meant by the term 'immiscible'?

The term 'immiscible' refers specifically to substances that do not mix or combine to form a homogeneous solution. This property is particularly relevant in the context of emulsions, which are mixtures of two immiscible liquids, such as oil and water. In an emulsion, even though the two liquids are combined, they remain separate and do not blend uniformly; instead, they form distinct layers or droplets within one another.

In contrast, when substances mix uniformly, they are termed as 'miscible', which means they can integrate to form a single phase. The idea of one substance dissolving another pertains to solubility rather than emulsification, while the notion that none can be separated does not accurately describe immiscibility, as immiscible substances can often be separated through physical means. Understanding immiscibility is critical when working with emulsions in cosmetic and skincare formulations, as it influences how ingredients interact and the stability of the product.