A radiochemical study of some neutron-deficient nuclides in the noble metal region has been undertaken, and several new chains identified. The method used to establish genetic relationships was that of timed chemical separations, where the parent activities are initially produced by cyclotron or linear accelerator bombardments. The following chains have been identified: $A=191:{\mathrm{Hg}}^{191}\stackrel{55 min}{\to }{\mathrm{Au}}^{191}\stackrel{3.0 \mathrm{hr}}{\to }{\mathrm{Pt}}^{191}\stackrel{3.0 \mathrm{day}}{\to }{\mathrm{Ir}}^{191},$ $A=189:{\mathrm{Hg}}^{189}\stackrel{\sim 20 min}{\to }{\mathrm{Au}}^{189}\stackrel{42 min}{\to }{\mathrm{Pt}}^{189}\stackrel{10.5 \mathrm{hr}}{\to }{\mathrm{Ir}}^{189}\stackrel{11 \mathrm{day}\mathrm{}(?)\mathrm{}}{\to }{\mathrm{Os}}^{189},$ $A=188:{\mathrm{Pt}}^{188}\stackrel{10.0 \mathrm{day}}{\to }{\mathrm{Ir}}^{188}\stackrel{41 \mathrm{hr}}{\to }{\mathrm{Os}}^{188},$ $A=187:{\mathrm{Au}}^{187}\stackrel{\sim 15 min}{\to }{\mathrm{Pt}}^{187}\stackrel{2.5 \mathrm{hr}}{\to }{\mathrm{Ir}}^{187}\stackrel{14 \mathrm{hr}}{\to }{\mathrm{Os}}^{187}.$

• Received 23 February 1955

DOI:https://doi.org/10.1103/PhysRev.98.1258