Solid solution
Solid in which components are compatible and form a unique phase.
Note 1: The definition “crystal containing a second constituent which fits into and is distributed in the lattice of the host crystal” given in refs., is not general and, thus, is not recommended.
Note 2: The expression is to be used to describe a solid phase containing more than one substance when, for convenience, one of the substances, called the solvent, is treated differently from the other substances, called solutes.
Note 3: One or several of the components can be
macromolecules. Some of the other components can then act as plasticizers, i.e., as molecularly dispersed substances that decrease the glass-transition temperature at which the amorphous phase of a
polymer is converted between glassy and rubbery states.
Note 4: In pharmaceutical preparations, the concept of solid solution is often applied to the case of mixtures of
drug and
polymer.
Note 5: The number of drug molecules that do behave as solvent of polymers is small. A
solid solution is a solid-state solution of one or more solutes in a solvent.