TABLE 46. io —-e—e—e Tissue ‘Bi/22Pp ———-—] Equitisrium Activity Ratios or THortum DauGcutTer Proptucts In SELECTED TissuEs Animal] Red bone marrow vert.) Man Code No. Batch No. 85 13098 vert.) Man 166 ~rernum) Man 166 i Duration |**Ra/#Th |“8Ac/“Ra |“*Th/“8Ra |*4Ra/28Th 22Ph /24Ra 22B1/22Ph ; ? 48d 26y Weighted mean Narrow (vert.)@ Matrix (vert.)© ~1.0 Man Man 85 166 13098 48d ? 26y F Weighted mean ~1.0 Jose Man Man ‘Man Man 66 83 85 166 ? 13098 13098 lly 26d 48d ? 26 F Weighted mean 1.0 Man Man 166 66 ? ? 26y lily Weighted mean Porvascular posit’? daughte: de-}| Rat Rat Rat Rat Rat Rat Rat Rat 65 67 TH2 TH3 TH4 TH5 73 72 13098 “ “ “ “ “ 099-40 “ 20d | 41d 18m 22m 12m 22m 38d 35d j Weighted mean Bile — 0.93 1.0 0.58 — 1.1 — — —_ 1.i 0.60 —_— —_ 0.21 _ 1.0 0.6 1.1 — 0.29 _— 0.89 1.1 2.4 1,02 0.82 -— 0.29 — 1.0 1.7 0.8 — _— —_ — ~1.0 0.86 0. 86 — 0.9 1,5 — 0.25 — — 0.90 ~1.2 0). 89 — 0.25 — 0.9 0.96 | — Dog 78 13098 21d ��� — — ~0.5 — — —_ 05 Lymph node ional rez t of th 0.21 _— — — 5 i 1.47 >1 >I — >1 2.1 1.7 0.89 ol] ~l ~] — 0.8 1.06 1.7 0.9 — — 0.68 | — | —_ — ul 1.0 ~2 | 1.08 — — — — 0.90 0.96 — — —_ — ~18 — — — 18 — — — — — — —_ 0.9 — — 0.97 — 1.08 ~] ~l 0.5 1.05 2.2 2.2 0.98 1.3 — — | — 0.94 ~I1 ~l 0.7 0.8 0.98 0.81 0.71 ~1 ~l 0.7 — — 0.82 0.9 0.8 ~7 6 ' Spongy marrow matrix from which the red bone-marrow was extracted by pressure. ‘) Spongy marrow matrix from which the red bone-marrow was completely extracted by meansof a jet of water. ‘' Hat tail at site of Thorotrast administration. } for this to happen. Thesize of the particles is such that '§ -ignificant proportion of the atoms they contain could - be in surface locations (~20%). Escape following a } lowenergy recoil may therefore be an important mechfp uem, especially for 728Th (vide infra). \ceording to the proposed recoil mechanism, the es»pe of recoiling atoms from the particles would be expectedl to depend strongly on the ratio of the particle f “Ize to the recoil range. The particles are reported to Fhe irregular in shape and probablyflat, and, there- F fore, we may provisionally regard them as being in} ‘e'mediate between a sphere and a plane. It is a fairly i “npie mathematical exercise to derive the relation- S) otis for the escape of recoiling atoms from particles se ° ‘hese two shapes, as illustrated in Figure 85. It is : Went from either of the curves that the proportion fF“ 'ccoiling atoms expected to escape depends strongly TABLE 47. Recorn ENERGIES OF THORIUM SERIES NUCLIDES Nucleus Transitionbywhich Maxierecon 228R a 228 AC 228Th 24R a 220Km 216Po 212Ph 212Ri a By Yy B,y a a a a Bx 70 keV 0.1 eV 16 eV 97 keV 103 keV 116 keV 128 keV 2.3eV 2087] a 116 keV 32P Gg B,y 19 eV on the particle size. In the case of *°8Ra, for example, the observed proportion was approximately 75% (28Ra/222Th = 0.25, Tables 42 and 43) which ob-