For a fixed integer n ≧ 1, and a
given ring R there exists a homomorphism ρ;R → Mn(K),K a commutative ring
such that every homomorphism of R into an n × n matrix ring Mn(H) over a
commutative ring can be factored through ρ by a homomorphism induced by a
mapping η : K → H. The ring K is uniquely determined up to isomorphisms. Further
properties of K are given.