By Kristen Gonsoir, Updated Aug 30, 2022
Solubility is the maximum amount of a substance that can dissolve in another under specified conditions. It ranges from nearly insoluble pairs, such as oil in water, to highly soluble combinations like ethanol in water. Dissolving is a physical process, not a chemical reaction.
A solution consists of two key components: the solute, which is the substance being dissolved, and the solvent, which facilitates dissolution. The state of the solvent—solid, liquid, or gas—determines the overall state of the solution.
When the solvent is water, solubility is often expressed as grams of solute per 100 grams of water. For gaseous solutes, the measurement may be given in grams of gas per kilogram (or liter) of water. These expressions reference the solvent’s mass before the solute is added.
After the solute has been incorporated, solubility can be reported in grams of solute per 100 grams of solution or grams of solute per liter of solution. A common metric is molarity, defined as moles of solute per liter of solution, which reflects the concentration of the dissolved species.
Solubility always refers to a saturated solution—the point at which no additional solute can dissolve under the given temperature and pressure. Therefore, solubility values are typically specified at a particular temperature and, when relevant, pressure to ensure accurate comparison.
