A survey has been made of the percentages of slow neutron-induced uranium fissions that give rise to the formation of various radioactive series. These percentages were obtained by measuring the number of $\beta$-disintegrations of a suitable member of the series after an irradiation under specified geometrical conditions and a quantitative chemical separation. The percentages found for the series thus far investigated vary from about 0.1 percent to 10 percent.

• Received 14 October 1940

DOI:https://doi.org/10.1103/PhysRev.59.52