If a person actually does or promises to do something which he is already bound to do, this is not sufficient consideration to support a promise by the other party.15 Thus the payment of an undisputed claim will not constitute a consideration for a promise to release the remainder of the claim.16 If, however, a person already indebted, under an obligation implied by the law makes an express promise to pay a certain sum of money in settlement of this liability, this previously existing liability is a good consideration for the promise and this new promise becomes a consideration for the release by the other party of the liability in its previously existing form.

13 Hawkes vs. Saunders, Cowper, 289.

14 Dusenbury vs. Hoyt, 53 New York, 521. 15 Havana Drill Co. vs. Ashurst, 148 I11., 115; 35 N. E., 175; Rundle vs. Kettering, 127 Iowa, 6; 102 N. W., 142. 16 Hastings vs. Lovejoy, 140 Mass., 261; Warren vs. Skinner, 20 Conn., 559; Ryan vs. Ward, 48 N. Y., 204.