. Radio-activity . plementaryto one another. The curves of rise and decay are shown graphi-cally in Fig. 82, curves I and II respectively. Godlewski observed that a solution of actinium, freed fromactinium X, gave out very little emanation, while a solution ofactinium X gave off the emanation in large quantity. Theamount of emanation from the solution was measured by observingthe activity produced in a testing vessel, similar to that shown inFig. 51, when a constant current of air was,passed through thesolution. The emanating power of actinium X decreased exponen-tially with the time at the sa
. Radio-activity . plementaryto one another. The curves of rise and decay are shown graphi-cally in Fig. 82, curves I and II respectively. Godlewski observed that a solution of actinium, freed fromactinium X, gave out very little emanation, while a solution ofactinium X gave off the emanation in large quantity. Theamount of emanation from the solution was measured by observingthe activity produced in a testing vessel, similar to that shown inFig. 51, when a constant current of air was,passed through thesolution. The emanating power of actinium X decreased exponen-tially with the time at the same rate as that at which the actinium Xlost its activity. At the same time the actinium solution increased * Eutherford, Phil. Trans. A. p. 169, Giesel, Ber. d. D. Chem. Ges. p. 775, Godlewski, Nature, p. 294, Jan. 19, 1905. 366 TRANSFORMATION PRODUCTS OF URANIUM, [CH. in emanating power, reaching its original value after about 60 behaviour of actinium and thorium is thus quite analogous, 100. and the explanation advanced to explain the decay and recoverycurves of thorium applies equally well to the corresponding curvesof actinium. The actinium X is produced at a constant rate from the parentmatter actinium, and is transformed according to an exponentiallaw with the time. The constant of change A, = 068 (day)~\ andthis value is characteristic of the product actinium X. As in thecase of thorium, the above experiments show that the emanationdoes not arise from actinium itself but from actinium X. Theemanation in turn breaks up and gives rise to an active deposit onthe surface of bodies. 212. Analysis of the active deposit from the emanation. Debierne * observed that the excited activity produced by actiniumdecayed to half value in about 41 minutes. Miss Brooks f showed * Debierne, C. B. 138, p. 411, Miss Brooks, Phil. Mag. Sept. 1904. X] THORIUM AND ACTINIUM 367 that the curves of decay of the excited activity after removaldepended upon the duration
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