Dihydraatti

Dihydraatti, in Finnish, is the term for a dihydrate in English: a chemical compound that contains two molecules of water of crystallization per formula unit. In such compounds, the two water molecules are incorporated into the crystal lattice and are essential to the structure. The formula is written with two waters of hydration, for example calcium sulfate dihydrate CaSO4·2H2O or copper(II) sulfate dihydrate CuSO4·2H2O. Dihydrates are common among inorganic salts and minerals and often crystallize from aqueous solutions under specific temperature and humidity conditions.

The water of crystallization can influence a substance's crystal habit, stability, solubility, and thermal behavior. Dihydrates may be stable at ambient conditions but can lose water upon heating (dehydration) or absorb water from humid air (rehydration). Dehydration typically yields anhydrous salts or lower hydrates, depending on the material.

Common examples and significance include gypsum (calcium sulfate dihydrate), a widely used mineral in construction; and copper(II) sulfate dihydrate, a laboratory reagent used for crystallization experiments. In minerals and pharmaceuticals, dihydrates are often favored for their stability and predictable solubility profiles.

In summary, dihydraatti refers to a two-water hydrate, a standard category of hydrated compounds whose properties are governed by their hydration state and environmental conditions.