21 APPENDIX 1 Table Al. Division of elements and masses important to fallout. Volatile at 1500°C Refractory at 1500°C Elements Ge Cd Be Nb As In Na Ba Se Sn Mn Rare Earths Br Sb Fe Th Kr Te Co U Rb I Cu Np Mo Xe Sr Pu Tc Cs Ru W Rh Au Pd Pb Am Cm Zr Ag Mass Numbers 74 75 = 90 101 ~ 139 92 100 181 ~ 203 142 180 204 242