Nondissolving

Nondissolving refers to the property of a substance that does not dissolve in a given solvent under specified conditions. When a solute fails to enter the solvent phase and remains as a separate solid, liquid, or dispersed phase, it is described as nondissolving in that solvent. Solubility is a spectrum; many substances are soluble to some degree, while others are effectively insoluble at a given temperature.

Several factors determine whether a substance dissolves: the chemical compatibility between solvent and solute, driven by polarity and hydrogen bonding; lattice energy of the solid; temperature; and, for gases, pressure. Substances with strong lattice energy or weak affinity for the solvent tend to be nondissolving. Examples include sand (silicon dioxide) in water, graphite in water, many polymers in water at room temperature, and glass in water. Some metals do not dissolve but may react or corrode; others may remain largely unchanged while interacting slowly with the solvent.

Testing solubility involves dissolution experiments and qualitative observations. Solubility is described as the maximum amount of solute that will dissolve in a given quantity of solvent at a specified temperature, forming a saturated solution. Substances that do not dissolve can form suspensions or dispersions rather than true solutions.

Applications of the concept of nondissolving appear in pharmaceuticals (where insoluble excipients are used to control release), coatings and pigments (which must resist dissolution in certain environments), and environmental science (where nondissolving particles contribute to persistence). The term is inherently relative, as a substance might be nondissolving in one solvent and soluble in another or at another temperature.