decahydrate

Decahydrate refers to a chemical compound that has incorporated ten water molecules (H₂O) into its crystal structure as water of crystallization. This term is commonly used to describe hydrated salts, where the water molecules are bound within the crystal lattice rather than being loosely associated or free. Decahydrates are a specific subset of hydrates, distinguished by their precise hydration level.

One of the most well-known examples of a decahydrate is copper(II) sulfate pentahydrate (CuSO₄·5H₂O), which loses five water molecules upon heating. However, the term "decahydrate" specifically applies to compounds that retain ten water molecules, such as certain metal sulfates, nitrates, or chlorides. For instance, some hydrated forms of magnesium sulfate (Epsom salt) or calcium chloride can exhibit decahydrate behavior under specific conditions, though these are less common than simpler hydrates.

The presence of water molecules in decahydrates can significantly affect a compound’s physical properties, such as solubility, melting point, and stability. When heated, decahydrates typically lose water gradually, forming anhydrous (water-free) forms. This dehydration process can be reversible, depending on the conditions, such as temperature and humidity. The loss of water often results in a noticeable change in the compound’s appearance, such as a shift in color or a reduction in mass.

In industrial and laboratory settings, decahydrates are important in processes requiring precise hydration states, such as in pharmaceutical formulations, chemical synthesis, or analytical chemistry. Their controlled dehydration can also be used to purify substances or adjust their reactivity. However, improper handling may lead to incomplete dehydration or unwanted side reactions, so careful temperature and environmental control is essential.