An end point corresponding to an energy of 2.8±0.1 Mev has been determined for the ${\mathrm{Fe}}^{53}$ 8.9-minute positron activity. ($\alpha ,p$) and ($n,p$) reactions on enriched ${\mathrm{Cr}}^{54}$ and ${\mathrm{Fe}}^{57}$ respectively failed to produce any activity in ${\mathrm{Mn}}^{57}$. The previously reported 1.3- to 2.3-hour activity of ${\mathrm{Cr}}^{55}$ was shown not to be produced by a ($d,p$) reaction on enriched ${\mathrm{Cr}}^{54}$ nor by an ($n,\alpha$) reaction on enriched ${\mathrm{Fe}}^{58}$. The 3.9-minute ${\mathrm{V}}^{52}$ activity is readily produced by a Cr ($d,\alpha$) reaction, using Cr enriched in isotope 54.

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