We prove that a finite
dimensional semisimple nil algebra over a field F which satisfies the identity
(1 + δ)z(x ∘ y) + (1 − δ)(x ∘ y)z = x(y ∘ z) + y(x ∘ z), where δ ∈ F and δ≠− 1∕2, is
anti-commutative. This result permits a further reduction in the problem of
classifying those varieties of power-associative algebras over F having the
property that squares of ideals are ideals and for which the nil algebras are not
pathological.