Watermiscible

Watermiscible, often written water-miscible, describes a substance that can mix with water to form a single, homogeneous solution across the available range of compositions at a given temperature. In practice, liquids that are completely miscible with water dissolve in any proportion, while some substances are only partially miscible and separate into two phases at certain ratios.

The ability of a substance to mix with water is determined by intermolecular forces, especially polarity and hydrogen bonding. Polar, hydrophilic molecules and small alcohols typically display complete water miscibility, whereas larger nonpolar organic compounds are often immiscible or only partially miscible with water. Temperature can influence miscibility, and the presence of salts can cause salting-out, reducing miscibility in some systems.

Common examples of water-miscible solvents at room temperature include methanol, ethanol, isopropanol, acetone, acetonitrile, and formamide. Glycerol and many other polyols are also completely miscible with water. Some ionic liquids and highly water-soluble salts dissolve readily in water, but they are typically described in terms of solubility rather than liquid-liquid miscibility.

Applications and implications: Water-miscible solvents are widely used in chemistry, pharmaceuticals, cleaning, analytical methods, and formulation science because they mix readily with aqueous systems, assisting dilution, extraction, and processing. Their behavior affects solubility, volatility, drying, environmental fate, and safety considerations, including flammability and toxicity.