The following data are abstracted from ex,¢ericental results, wherein a thin paz souree prepared by soaking a filter payer in a solution of phosphates, allowing it to dry, and then weasuring surface dose rates with a surface ionization chanber.® Thickness of source 9.6 ng/ex* Activity of source 7740pale Surface dose rate . 0.127 rep/see 457 Dorage rute at depth of x centimeters ie repe/hr ‘ oF «5x ~ Zheoret ically R = sos (for ¥32) Subst ituling abowe dates nw Re 95 Noe72-5) (9.007) | go DOL /ty 2 = 7,0 C repe/br let C® 77po/ex* Then Rk» 7 x 77 a“ = $39 repa/br at 7 ag/er® (17°) “nifecE is xteral Zirkle, Raymond X. MeGrawiiill Book Company, 1951. (4