Ylikyllästymistä

Ylikyllästymistä, a Finnish term, translates to "oversaturation" and refers to a condition where a substance or a solution contains more of a solute than it can normally hold at a given temperature and pressure. This occurs when a solution is cooled below its saturation point without the solute precipitating out. The excess solute remains dissolved in a metastable state.

This phenomenon is not thermodynamically stable. Even slight disturbances, such as adding a seed crystal of the solute, introducing dust particles, or mechanical shock, can trigger rapid crystallization. The excess solute will then precipitate out until the solution reaches its normal saturation level.

Oversaturation is a crucial concept in various scientific and industrial processes. In crystallization, it is often intentionally created to promote the formation of crystals. For example, in the production of sugar, salt, and pharmaceuticals, controlled oversaturation leads to the desired crystal size and purity.

Conversely, oversaturation can be problematic. In industrial pipelines, it can lead to scaling or fouling if the excess solute precipitates out and adheres to surfaces. Understanding and controlling oversaturation is therefore essential for efficient and safe operation in many chemical engineering applications. The term is also used more broadly in other contexts to describe a state of being overwhelmed or having too much of something, although its primary meaning is rooted in chemistry.