The ability or tendency of one substance to blend uniformly with another, e.g., solid in liquid, liquid in liquid, gas in liquid, gas in gas. Solids vary from 0–100% in their degree of solubility in liquids, depending on the chemical nature of the substances; to the extent that they are soluble they lose their crystalline form and become molecularly or ionically dispersed in the solvent to form a true solution. Examples are sugar/water, salt/water. Liquids and gases are often said to be miscible with other liquids and gases rather than soluble. Thus nitrogen, oxygen, and carbon dioxide are freely miscible with each other and air is a solution (uniform mixture) of these gases.The physical chemistry of solutions is an extremely complex mathematical subject in which the principles of electrolytic dissociation, diffusion, and thermodynamics play controlling parts. Raoult's law and Henry's law are also involved. See Miscibility; Solution, True.
