The heat output of tritium has been determined by calorimetry. If one assumes a half-life of 12.26 years, the average beta energy is shown to be 5.57±0.1 kev. This is considerably lower than the value previously reported, and an explanation of this discrepancy is offered.

• Received 2 December 1957

DOI:https://doi.org/10.1103/PhysRev.109.2091