The Atomic Masses of the Heavy Elements

Comparisons have been made between a series of different atomic masses by means of a double-focusing mass spectrograph. The small displacement between the positions of multiply charged ions of one mass and atoms of another mass is measured and gives a value for the difference in the packing fractions of the two atomic masses. The following pairs of ions have been compared: ${\mathrm{O}}^{+}$-${\mathrm{Ti}}^{+3\mathrm{}}$, ${\mathrm{C}}^{+}$-${\mathrm{Ti}}^{+4\mathrm{}}$, ${\mathrm{N}}^{+}$-${\mathrm{Fe}}^{+4\mathrm{}}$, ${\mathrm{O}}^{+}$-${\mathrm{Cu}}^{+4\mathrm{}}$, ${\mathrm{Al}}^{+}$-${\mathrm{Ag}}^{+4\mathrm{}}$, ${\mathrm{Cu}}^{+}$-${\mathrm{Au}}^{+3\mathrm{}}$, ${\mathrm{Ti}}^{+}$-${\mathrm{Au}}^{+4\mathrm{}}$, ${\mathrm{Cu}}^{+}$-${\mathrm{Pt}}^{+3\mathrm{}}$, ${\mathrm{Sn}}^{+}$-${\mathrm{Th}}^{+2\mathrm{}}$, ${\mathrm{Sn}}^{+}$-${\mathrm{U}}^{+2\mathrm{}}$, ${\mathrm{Sn}}^{+}$-Ac${\mathrm{U}}^{+2\mathrm{}}$, ${\mathrm{Zr}}^{+}$-${\mathrm{W}}^{+2\mathrm{}}$(91, 92), ${\mathrm{Mo}}^{+}$-${\mathrm{Pt}}^{+2\mathrm{}}$(96, 97, 98), ${\mathrm{Mo}}^{+}$-${\mathrm{Ir}}^{+2\mathrm{}}$, ${\mathrm{Pd}}^{+}$-${\mathrm{Pb}}^{+2\mathrm{}}$(102, 104), ${\mathrm{Rh}}^{+}$-${\mathrm{Pb}}^{+2\mathrm{}}$, ${\mathrm{Pd}}^{+}$-${\mathrm{Tl}}^{+2\mathrm{}}$, ${\mathrm{Pd}}^{+}$-${\mathrm{Bi}}^{+2\mathrm{}}$, ${\mathrm{Ru}}^{+}$-${\mathrm{Os}}^{+2\mathrm{}}$(96), ${\mathrm{Ru}}^{+}$-${\mathrm{Pt}}^{+2\mathrm{}}$(99), Pd-${\mathrm{Ga}}^{+}$. Less exact comparisons have also been made between the following pairs: ${\mathrm{Mo}}^{+}$-${\mathrm{Os}}^{+2\mathrm{}}$(94, 95, 96), ${\mathrm{Ag}}^{+5\mathrm{}}$-${\mathrm{Zn}}^{+3\mathrm{}}$, ${\mathrm{Na}}^{+}$-${\mathrm{Zn}}^{+3\mathrm{}}$, ${\mathrm{Sn}}^{+}$-${\mathrm{Ta}}^{+3\mathrm{}}$, ${\mathrm{K}}^{+2\mathrm{}}$-${\mathrm{Ru}}^{+5\mathrm{}}$, ${\mathrm{Ni}}^{+2\mathrm{}}$-${\mathrm{Ru}}^{+5\mathrm{}}$, ${\mathrm{Al}}^{+}$-${\mathrm{Pd}}^{+4\mathrm{}}$, ${\mathrm{Fe}}^{+}$-${\mathrm{Ag}}^{+2\mathrm{}}$. The values deduced for the packing fractions of titanium, iron, and copper, and the probable values for zinc, silver, gold, and platinum are higher than those to be expected from Dr. Aston's packing fraction curve by about 2 parts in 10,000.