4. (Chem.Phys.) The act or process by which a body (whether solid,
liquid, or gaseous) is absorbed into a liquid, and, remaining or
becoming fluid, is diffused throughout the solvent; also, the product
resulting from such absorption.
When a solvent will not take in any more of a substance the solution is
said to be saturated. Solution is of two kinds; viz.: (a) Mechanical
solution, in which no marked chemical change takes place, and in which,
in the case of solids, the dissolved body can be regained by
evaporation, as in the solution of salt or sugar in water. (b) Chemical
solution, in which there is involved a decided chemical change, as when
limestone or zinc undergoes solution in hydrochloric acid. Mechanical
solution is regarded as a form of molecular or atomic attraction, and
is probably occasioned by the formation of certain very weak and
unstable compounds which are easily dissociated and pass into new and
similar compounds.
This word is not used in chemistry or mineralogy for fusion, or the
melting of bodies by the heat of fire.