Comparative Retentions of the Nuclear Isomers of Br80 in the Propyl Bromides

By experiments on retention, which is defined as the fraction of the radioactivity resisting aqueous extraction, we find, for propyl bromides irradiated in paraffin at a distance of two centimeters from the source with unfiltered neutrons: $$\begin{array}{ccc}& R_{({\mathrm{Br}}^{80}\text{(18\hspace{0.17em}}\min \mathrm{))}}& R_{({\mathrm{Br}}^{80}\text{(4.4\hspace{0.17em}}\mathrm{hr}\mathrm{))}}\\ \mathrm{Normal\; propyl\; bromide}& \text{0.72±0.05}& \text{0.85±0.05}\\ \mathrm{Isopropyl\; bromide}& \text{0.37±0.02}& \text{0.58±0.03}\end{array}$$ The different sources of error are examined and eliminated. The addition of free bromine, with the purpose of blocking the impurities, left a difference in the retention of the two isomers. An interpretation is suggested. The percentage of Br(18 min) of isomeric transition in the free state proceeding from Br(4.4 hr) in the bound state, is found to be 16 percent for the normal propyl bromide and 40 percent for the isopropyl bromide.