In this paper first we show that the iteration

of a non zero derivation d on a semi-prime

-ring R is not a derivation, and hence d can not be nilpotent. Then we see that if R is prime and

, are positive derivations on R with

a derivation, then at least one of these derivations must be zero. Finally, taking R to be a semiprime f-ring, we show that if for every

is central, then, under some mild conditions, there is a nonzero inner derivation

on R such that

. These results generalizes and improves the ones in [3], [8], and [9]. And show that imposing an order on a ring, making it an ordered ring, gives stronger results.