Results for 3564 events of the type np → pp π − are presented. The events were obtained in a hydrogen bubble cjamber exposed to a neutron beam. The incident momentum distribution of the events is approximately uniform in the range 1.0 – 7.5 GeV/ c. The physical distributions are found to be in good agreement with the predictions of a one pion exchange model incorporating a recent phase shift analysis of pion-nucleon scattering and using the off-mass-shell corrections of Benecke-Dürr and Dürr-Pilkuhn. Certain discrepancies between our results and previous studies of the reaction in deuterium are found. In particular we find no evidence for anomalous N ∗ (1450) production and find discrepancies in certain momentum transfer distributions.