  A general model for the fragmentation of a two-component system (e.g. protons
and neutrons) is proposed and solved exactly. The extension of this model to
any number of components is also shown to be exactly solvable. A connection
between this models and the permutation group is discussed. The notion of
isotopic equivalence is defined in order to evaluate the equivalence of these
models to earlier one-component models. All the one-component models considered
in earlier papers are shown to be equivalent to a particular class of
two-component models. A simplified model applicable to the case of nuclear
fragmentation is introduced and analyzed. Modifications to this model to
include effects such as pairing and Coulomb interactions are discussed.
