The theory of differential modules which is developed in [2] is used here for the study of differential rings containing the rational numbers Q (frequently called Ritt algebras). This is done by introducing differential module structures on certain modules of Kihler differentials. The introduction of Kahler differentials allows some quick proofs of known results in differential algebra. In ? 3, on the way to the proof of the main theorem of this paper (see ? 4), some of these applications of the theory have been noted. For the theorems of commutative algebra needed in the writing of this paper, we have used [1] as a reference. These references have been made with enough care so that a prior knowledge of [1] is in no sense a prerequisite.