The Journal of the American Chemical Society VOL. 53
JULY, 1931
No. 7
THE RADIOACTIVE CONSTANTS A S O F 1930. REPORT OF THE INTERNATIONAL RADIUM-STANDARDS COMMISSION'~2 BY M. CURIE,A. DEBIERNE, A. S. EVE,H. GEIGER,0. HA", S. C. LIND,ST. MEYER, E. RUTHERFORD AND E. SCHWEIDLER RECEIVED JUNE13, 1931
PUBLISHED JULY8, 1931
Following the reorganization of the International Union of Chemistry and of the International Atomic Weights Commission, the need has arisen for the publication of special Tables of the Radioactive Constants. This responsibility has been assumed by the International RadiumStandards Commission chosen in Brussels in 1910, which has expressed its willingness to cooperate with the International Union. Besides the members of the Committee, the following have taken part as experts: J. Chadwick, I. Joliot-Curie, K. W. F. Kohlrausch, A. F. Kovarik, L. W. McKeehan, L. Meitner and H. Schlundt, to whom it is desired to express especial obligations. The following report will also be published simultaneously in the Physikalische Zeitschrift, Review of Modern Physics, Philosophical Magazine and Journal Physique et le Radium. General Remarks on Symbols and Terms The symbols are provisionally retained as used in the texts of St. MeyerE. Schweidler, F. Kohlrausch, and E. Rutherford, J. Chadwick and C. D. Ellis, as well as in the Physikalische Zeitschrift, 19, 30 (1918); Zeitschrift fur Elektrochemie, 24,36 (1918); and Jahrb. Rad. u. Elektr., 19,344 (1923). For the three radioactive gases the use of the terms radon (Rn), thoron (Tn), and actinon (An) is recommended (2.anorg. Chem., 103, 79 (1918)), and as general term for elements of atomic number 86 the retention of the word "emanations" (Em) for the three isotopes. The words emanate, emanating power, etc., are retained. To facilitate desirable changes and additions in subsequent years it is requested that data, notes and suggestions be sent to: Prof. Dr. Stefan Meyer, Institut fur Radiumforschung, Boltzmanngasse 3, I X Vienna, Austria. A summary of literature on decay constants and ranges and on absorption coefficients is to be published in other versions of this report, to appear in the July issue of the Physikalische Zeitschrift and of the Review of Modern Physics.
2438
INTERNATIONAL RADIUM-STANDARDS COMMISSION
Vol. 5 3
The designation “radio-lead” is restricted to the natural radioactive mixture of lead isotopes in minerals and is not used to designate RaD. RaG, ThD and AcD shall be called uranium-lead, thorium-lead and actinium-lead, respectively. The mixture of RaG and AcD will also be designated uranium-lead. Instead of the designation “Isotopic Weight” (Poids isotopique) as used in the earlier “Tables internationales des 616ments radioactifs” for the whole numbered atomic weights or the number of hydrogen nuclei, the word “Proton number” is proposed. Symbols : UI, UXI, UX2, UTI, Io, Ra, Rn, RaA, RaB, RaC’, RaC”. RaD, RaE, RaF=Po, RaG, UY, UZ. Th, MsThl, MsTh,, RdTh, ThX, Tn, ThA, ThB, ThC’, ThC”, ThD. AcU, Pa, Ac, RdAc, AcX, An, AcA, AcB, AcC, AcC‘,AcC“, AcD. Pa is for protactinium (not Proto-actinium). E m is the joint symbol for Rn, Tn and An.
The following report contains: I, Basic Values; 11, Units; 111, Constants.
I. Basic Values (1) R. T. Birge, Phys. Rev., (2) 33, 265 (1929), Supplement 1.1-73, July 1929 ( l a ) R. T. Birge, ibid., (2) 35, 1015 (1930) (2) H. L. Curtis, Bur. Stand. J . Research, 3, 63 (1929) c = 299790 km./sec. c = 299796 (3) Michelson, 1927 (older value 299850) c = 299778 (4) Karolus and Mittelstaedt, 1928 (4a) E‘.Grotrian, Nuturwiss., 17, 201 (1929) e = 4.770.10-10 E. S. U. (5) R. A. Millikan, Science, 69, 481 (1929) By Rontgen ray spectroscopy (6) J. A. Bearden, Proc. Nat. Acad., 15,528 (1929) e = 4.810~10-’” ( 7 ) A. H. Compton, Franklin J., 208, 605 (1929) 4.793 (8) E. Backlin, Nature, 123, 409 (1929) 4.82 (9) H. A. Wilson, Phys. Rev., (2) 34, 1493 (1929) 4.7797 (10) W. N. Bond, Phil. Mag., (7) 10, 994 (1930) 4.821 (11) J, M. Cork, Phys. Rev., (2) 35, 128 (1930) (12) W. H. Houston, ibid., (2) 30, 608 (1927) c/m, = 1.7606.107 spectroscopic 1.7606.107 spectroscopic (13) H. D. Babcock, Astrophys. J., 69, 43 (1929) (14) F. Kirchner, Physik. Z., 31, 1073 (1930) 1.7602 Deflection of cathode rays 1.7598 * 0.0025 Ann. Physik, (5) 8, 975 (1931) (15) C. T. Perry and E. L. Chaffee, Phys. Rev., (2) 36, 1.761 Deflection of cathode 904 (1930) rays (10) A . Upmark, 2. Physik, 55, 569 (1929) (17) A. R. Olpin, Phys. Rev., (2) 36, 251 (1930)
Velocity of Light c = 2.9980.10’0 cm./sec.
Literature, (l), (2), (3), (4)
11. Chemical Units
The chemical atomic weights and quantitative relations are based on 0 = 16.0000. The discovery of the oxygen isotopes 01* and 01’in the
July, 1931
THE RADIOACTIVE CONSTANTS
2439
estimated proportions: 0l60 :" : 018 = 10,OOO:l:8 requires a sharper definition. In contrast to the chemical definition, 0 = 16.0000 for the isotopic mixture, it is proposed for questions of atomic structure and radioactivity in the sense of Aston's measurements to choose 0l6= 16.0000. For the isotopic mixture in the ratios (very uncertain) given above, 0 = 16.0017, R. Mecke and W. H. J. Childs (2.Physik, 68, 362 (1031), estimate 0 = 16.0035 * 0.0003). Corresponding to 016= 16.0000, other values are H = 1.0078 (Aston) He = 4.00216 (Aston) mo of 018/16.00 = 1.00000 mo (proton) = 1.0072 mo (alpha) = 4.00106 mo (electron) = 0.000548 for e/mo = 5.2765.10" E. S. U.
absolute: absolute: absolute: absolute: absolute:
1.6ti2.10-24 g. 6.5994.10-24g. 1.6490.10-24g. 1.661.10-24g. 6.598.10-24g.
absolute:
9.040.10-28 g.
Faraday Number F = 96489 *5 abs. coulomb (1) 96494 *l internat. coulomb
Elementary Charge e = 4.770.10-'0 E. S. U. (Millikan) (5) (4.9.10-10 E. S. U. by x-ray spectroscopy (6), (7), (8), (9), (lo), (11)
Specific Charge elm0 = 1.760.107ahs. magnet. U./g. [spectroscopic (I), electron deflection (14), ( I s ) ] 5.2765.10" E. S. U./g. 1.769.107abs. mag. U./g. Older deflection expts. (l),(4a), (10)
= 5.303.1017 E. S. U./g.
Planck's Constant It
= 6.547.10-27 erg. sec.
(1)
= 6.5596.10-27 erg. sec. (10) = 6.591.10-2' erg. sec. (4a) = 6.541.10-27 erg. sec. (17)
Avogadro's Number L
=
Fc/e = 6.0644.1OZ3mol.-' for e = 4.770.10-10
= 6.0265.10a3mol.-' for e = 4.80.10-10 1 Year = 365.24223 days = 3.155693.107sec. 1 Sec. = 3.168876.10-8 yr.
Derived Values p
= v/c
C*
8.988004~1O20
1
?=-
di-q3
m =mor) 2e = 9.540.10-'O moc2 = 5.9303.10-3 for a-particles md2 = 8.1207.10-7 for elm, = 5.2765.10" E. S. U./g. for P-particles m&/'e = 6.2162.106 for a-particles m d 2 / e = 1.7034.103for e/mo = 5.276510'' E. S. U./g. for P-particles
2440
INTERNATIONAL RADIUM-STANDARDS COMMISSION
Vol. 53
Kinetic energy E = mo c2 (7- 1) for a-particles: E = 5.9303.10-8 ( q - 1) erg. Kinetic energy in volt-electrons for p-particles: E = 8.1252.10-’ (q-1) erg. Velocity in equiv. volts P = 299.80E/2e = 3.1426.1011Efor a-particles P = 299.80E/e = 6.2851.10l’E for p-particles
Product of the magnetic field strength and the radius of curvature of the path : log R = (rnoc2/2e)q(3= 6.2162.1O6qpfor a-particles log R = (moc2/e)qp = 1.7034.103q p for p-particles X = hc/E = 1.9628.10-16/E for h = 6.547.10-27 X = hc/E = 1.9637.10-16/E for h = 6.55.10-27
2 = number of a-particles emitted per second from 1 g. of Ra Earlier literature to 1926, St. Meyer-E. Schweidler, “Radioaktivitat,” p. 401. (1) H. Jedrzejowski, Compt. rend., 184, 1551 (1927); Ann. Physik, 2 = 3.50.101” 9, 128 (1928) 3.7.1010 (2) I. Curie and F. Joliot, Compt. reizd., 187, 43 (1928) (3) H. J. Braddick and H. 31. Cave, Proc. Roy. SOL.(London), 121, 368 (1928); N a t u r e , 122, 789 (1928); also G. Ortner, Wien. Ber. 138, 117 (1929); Mitt Ra-Inst., Nr. 229 3.69 (4) F. A, Ward, C. E. Wynn-Williams and H. M. Cave, Proc. Roy. 3.66 SOL.(London), 125, 713 (1929) ( 5 ) S. H. Watson and M. C. Henderson, ibid., A118,318 (1928) (indirect) 3.72 (6) G. Hoffman, Physik. Z., 28,729 (1927); H. Ziegert, 2.Physik, 46, 668 (1928) 3.71 3.72 (7) G. Ortner and C. Stetter, ibid., 54, 475 (1929) (8) L. Meitner and W. Orthmann, ibid., 60, 143 (1930) 3.68 (9) E, Rutherford, J. Chadwick and C. I). Ellis, “Radiations of Ra3.70 dioactive Substances,” 1930, p. 63
NoTE.-The chief source of error lies in the value for the radium equivalent of the preparation (e. g., of RaC). This arises from the decay curve of RaB-RaC. The standardization is not exact to 0.5 because the standards are not more accurate than this and on account of the different shapes of standard and unknown the comparison involves further inaccuracy. Moreover, in the washing of the preparation with alcohol to remove residual radon, RaB is dissolved in excess of RaC [Mitt. Ra. Inst., No. 254; mien Ber., 139, 231 (1930)l. The theoretical curve is thereby disturbed in the first part of the decay of the preparation so that differences of 1% in the value of active deposit result. This error would cause a minimal value of is recommended in accord with lit. (9). 2. Use of the value 3.7~10’~ Ratio Ra:U in Old Unaltered Minerals Earlier Literature: St. Meyer-E. Schweidler, “Radioaktivitat,” 1927, 398, pp. 404-406, Lit. Nr. 7.22.23. V. Chlopin and M. A. Paswick, Akad. Leningrad (1928) (Russian). (In samples from the same location values varying due to chemical changes are found from 2.18 to 4.17.10-’. Compare also Lind and Whitternore, THISJOURNAL, 36, 2066 (1914). The recommended value is Ra/U = 3.4.10-7; U/Ra = 2.94.108.
July, 1931
2441
T H E RADIOACTIVE CONSTANTS
Basic Values for the Calculation of the Number of Ion Pairs Produced by One a-Particle k = koR"8 and calculation of velocity from v3 = uoRo All data refer to 0 and 760 mm. As basis for ko. Z k = 8.18.1016(Meyer and Schweidler, "Radioaktivitat," 1927, p. 189), and Z = 3.7.10'O For RaC': R O = 6.58 cm. (see table of ranges) k = 8.18~101'/3.7~10'"= ko 6.58L ko = 6.296.10' Based on Ro = 6.60 and Z = 3.72.10'0 ko = 13.253.10~ Based on R O = 6.60 and Z = 3.70.1010 ko = 6.283.10' Recommended: ko = 6.3.10'
For ao, different values are obtained according to the choice of RaC', ThC' or Po as reference. This may mean that the relation v 3 = aR is not exact and that the definition of the range (Geiger-Henderson) as the intercept of the descending straight line of the Bragg's curve with the abscissa has no theoretical basis. For RaC' For ThC' For Po
R O = 6.58 Ro = 8.168 Ro = 3.67
= 1.022.108 = 2.054.108 v = 1.593*108 21
21
uo = a. = a0 = Recommended: uo =
1.0790.1027 a: 1 0609.1027 a: 1.1015.102' a:/' 1.08.10?7
a: a
1.026.109 1.020,109 = 1.032.108 = 1.026.109 =
=
which differ only slightly from the constants in use For 3Ro= 6.60 v = 1.922.108 a0 = 1.0758.10274aO'18= 1.0246.10S (Meyer-Schweidler, p. 629)
Radium content is expressed gravimetrically in grams or mg. of elemental radium, regardless of its state of chemical combination. However, it is always desirable to know the total weight and nature of the compound, with reference to Ra concentration.
Radon (Radium Emanation) 1 Curie is the quantity of Rn in equilibrium with 1 g. Ra 1 Curie Rn has the volume 0.66 cu. mm. a t 0" and 760 mm. 1 Curie (Rn without decay products) can with complete utilization of the a-particles maintain by its ionization of air a saturation current of 2.75.10' E. S.U. (0.92 milliampere)
Sub-units are millicurie, microcurie, etc. For the Rn content of waters and gases the sub-unit milli-microcurie ( is frequently used. 1 Eman = curie per liter (10-13 curie/cc.) is a term used since 1921 for the Rn content of the atmosphere as a concentration unit. 1 Mache Unit (1 M. E.) is a concentration unit referred to the Rn content of 1 liter of water or gas, etc. It is that quantity of Rn per liter which without decay products and with complete utilization of the a-particles 8 The basic value 6 60 mas the mean of the values of G. H. Henderson, Phil. Mug., [6] 42, ,538 (1921), 6 592, and of H. Geiger, 2. Physik, 8, 45 (1921), 6.608. To Ro the corresponding value at 15" is RIS= 6.963 cm. 4 See Rutherford, Chadwick and Ellis, Ref. (9), p. 86.
2442
I N T E R N A T I O N A L RADIUM-STANDARDS COMMISSION
VOl. 53
can maintain by its ionization of a ira saturation current of E. S. U. 1 M. E. corresponds to 3.64.1O-lO curie/liter = 3.64 Eman. It is recommended to extend the use of the term curie to the equilibrium quantity of any decay product of radium. One must then specify the element, as 1 curie Rn, for example. The Commission does not favor its extension to members outside the Ra family. On the other hand, the unit quantity of any radioactive element may be expressed in terms of the mass equivalent to 1 g. of Ra with respect to the effects of the rays or to the number of atoms decaying per second. In the latter sense one defines: 1 mg. of Ra equivalent as that quantity of any radioactive element for which the number of atoms decaying per second is the same as that for 1 mg. of Ra (3.7.10’ atoms/sec.). Since, however, the determination of the number of atoms decaying per second can seldom be made directly, the number will much more frequently be obtained indirectly from radiation effects. Polonium.-“1 Curie Po” = that amount which, equivalent to 1 gram of Ra, emits 3.7.10‘O a-particles per sec. “1 Curie Po” = quantity in radioactive equilibrium with 1 gram of Ra, 2.24.10-* g. Po. That quantity of Po whose a-radiation directed to one side only is fully utilized to ionize air and which can support a current of 1 E. S. U. corresponds to 1.68.10-’O g. of Po or 0.75*10-ecurie of Po. 1 Curie of polonium would in the utilization of its rays in all directions support a saturation current in air of 2.66*106E. S. U. l Microcurie of Po (one sided radiation) = 1.33 E. S. U. Mesothorium.-“ 1 mg. MsTh” usually signifies the y-ray equivalent of 1 mg. of Ra-RaC, compared after absorption by 5 mm. of lead. This definition is for many reasons (dependence on the age of the preparation and on the experimental conditions (see Meyer-Schweidler, 1927, pp. 496-497)), inexact and open to criticism. All determinations of content of Ra, Rn, MsTh, Po, etc., must be exactly dated, of course.
111. Radioactive Constants2 General Remarks For UI it is to be noted that the calculation is made on the basis 2 = 3.70.1O1O a/sec.; Ra/U = 3.40*10-7; Avogadro No. = 6.O64.1Oz3,with no account taken of the branching of the Ac Series. A correction for this would be so dependent on the value of T assumed for AcU that it would have little significance a t present. In any case, however, the values given above are for T and r upper and for X lower limits. For UX1, the lowest value T = 23.8 (1) is mentioned as well as the one preferred by the Commission. In the Table for R, v , k (Range, Velocity, Ion Production) the directly The calculation of the other values for observed values are denoted by
+.
July, 1931
2443
THE RADIOACTIVE CONSTANTS
v and k was made by using the basic values denoted KO and a. given on page 2441.
++, with the data for
gives according to the ranges of Laurence improbably low values for T (5). Direct determination (50) gives T = 3.4.106 years in good agreement with the range determinations of Hoffman-Ziegert (42). The adoption of 3.106 years is recommended. Rn The two best determinations made recently, W. Bothe, Z . Physik, 16, 226 (1923), T = 3.825 * 0.003 days, and I. Curie and C. Cham%, Compt. rend., 178, 1808 (1924); J . phys., [6] 5, 328 (1924), T = 3.823 * 0.002 days, agree within the limits of experimental error. During the first day, their differences in Rn decay by the hour are scarcely noticeable in the fourth place. For T = 3.823 days extended tables have been published by C. Chamik, M. Cailliet and G. Fournier [Paris, Gauthier-Villars, 19301.
UI1
Radium E Earlier accepted value L. Bastings, Phil. Mug., 48, 1075 (1924) G. Fournier, Compt. rend., 181, 502 (1925) L. F. Curtiss, Phys. Reo., 27, 672 (1926) J. P. McHutchison, J. Phys. Chem., 30, 925 (1926)
4’85 days 4.985 days 4.86 days 5.07 days 4.87 days
11,
Recommended: T = 5.0 days, and T = 4.9 days
For RaC’: see Lit. (15), (16), (16a) in Physik. Z., July, 1931. For ThC’: Mme. Curie has recently calculated from the Geiger-Nuttall Law: X = about log sec.-l. In view of the, great uncertainty attaching to the values for ThC’, 0. Hahn and L. Meitner propose to be content with the statement: T = 10-6 sec. AcC”: A. F. Kovarik points out that 150 curves are found to give T = 4.71 min., while Albrecht has only 9 curves for T = 4.76 min. Both values are given in the table. URANIUM FAMILY At. wt. = atomic weight; P. no. = proton number; at. no. = atomic number; yr. = years; d. = days; h. = hours; m. = minutes; s. = seconds; T = half period; 7 = average life; X = decay constant; ( ) indicates earlier values still in use T x 7 Literature Uranium I UI 4.4.109yr. 1.6.10-1°yr.-’ 6.3.109yr. At. wt. 238.14 1.4.1017~. 5.0.10-’8~.-1 2.O.lO”s. Cf “Remarks” 92 above At. no. P. no. 238 Cranium X1 UXI 24.5d. 2.83.10-*d.-’ 35.4d. 51 2.12.10%. 3.28.10-7~.-’ 3.05.106s. At. no. 90 23.8d. 2.90.10-*d.-’ 34.4d. P. no. 234 2.06.10%. 3.37.10-’~.-’ 2.97.106s. Uranium X p EX2 1.14m. 0.61m.-’ 1.64m. (51) (3a) (Brevium) 91 68.4s. 1.01~10-*~.-‘98.7s. 2, 3 ca. 99.65% 234 Uranium 2 UZ 6.7h. 0.103h.-’ 9.7h. ca. 0.35y0 91 2.4.1O4s. 2.87.10-%.-’ 3.5.104s.
1 1
234
I-ranium I1
VI1 92 234
3.105.~. 2.3.10-6yr.-1 4.3.106yr. 9 . 4 ~ 1 0 ’ ~ ~ . 7.4.10-14~.-’ 1.4.10’3s.
4, 5
2444
INTERNATIONAL RADIUM-STANDARDS
COMMISSION
URANIUM FAMILY (Concluded)
x
T
Uranium Y ca 3%
Ionium Io At. no. P. no.
UY 90 231 or 230
90 230
Radium Ra 88 226 Radon Rn At. no. P. no.
86 222
Radium A RaA 84 218 Radium B RaB 82 214 Radium C RaC 83 214 Radium C’ RaC’ 99.96% 84 (99.97%) 214 Radium C” RaC” 0.04% 81 (0.03%) 210 Radium D RaD 82 210 Radium E RaE 83 or 210
Radium F RaF(Po) Polonium 84 210 Radium G RaG Uranium lead 206.016 82 206
24.6h. 1.03d. 8.L?81O4s.
7
IONIUM-RADIUM FAMILY T x 7 8.3.10-6yr.-1 1.2S1Osyr. 8.3.104yr. 2.6*10’2~. 2.6,10-’a~.-1 3.8.10’*~. 1590yr. 5.02.10’0~.
Literature
2.82.10-*h.-’ 35.621. 0.675d.-l 1.48d. 7.81.10-6s. - l 1.28.105s.
Literature
7, 8, 8a
4.36.1O-‘yr. -l 1.38.10-”~.-’
2295yr. 7.24.10’%,
3.825d. 3.3O5.1O5s. 3.823d. 3.3O3.1O6s.
0.1812d.-’ 2.097.1O-C.-l 0.1813d.-’ 2.098.10”~.-‘
5.518d. 4.768.106s. 10 5.5156 Cj. Remarks 4.765-105.
3.05m. 183s.
0.227m.-l 3.78.10-%. -1
4.40m.
i
26.8m. 1.61.103
~ .
19.7111. 1.18.1O3s. ca. 10-6s.
1.32111. 79.2s. 22yr. 6.94.106s.
I
4.9d.
4.26.105s.
[ %:3”2d:106s.
264s.
9
11 51
2.5Y.10-2m.-1 38.7m. 4.3 1.10- 4 ~ . 2.32.108s.
-’
3 .5l,lO-*m. -l 28.5m. 5.86.10-4~.-’ 1.71.10%. lo%.-’
10 -6s.
0.525m1.-’ 8.7.10-3~.”
1.9m. 115s.
0.0315yr. 317 y r . I.oo.Io-~s.-~ 1.00.109~. 0.141d.-’ 1.G3,10-6~.-’ 0.139d.-’ 1.61.10-6~.-~
140d. 4.95.10-3d.-’ 1.21~107~. 5.73.10-8~.-’
7.07d. 6.13.106s. 7.2d. 0.22.105s. 202d. 1.75.107s.
12
13, 14 15, 16 16a 17
18, 19, 20
21
22, 23
July, 1931
2445
T H E RADIOACTIVE CONSTANTS
ACTINIUM FAMILY T x Actinium Uranium AcU
ca.
108
Literature
r
to 109yr.
24
Uranium Y, see Uranium Family 2.17.10-5yr.-1 4.6.1O4yyr. 3.2.104yr. l.O1~10~*S. 6.86.10 -'3 ~ . 1.46.10"~.
Protactinium Pa 91 231 Actinium Ac 89
13.5yr.
{
::::13::20 : yr.
227
18.9d. 1.63.106s.
Radioactinium RdAc 90 227 Actinium X AcX 88 223
I 11.2d.
86 219 Actinium A AcA 84 215 Actinium B AcB 82 211 Actinium C AcC 83 211 Actinium C' AcC' 84 0.32% 211 Actinium C" AcC" 99.68% 81 207
1 27,28
9.851O6s. 3.92s.
2.10-3s.
347s. -1
2.88.10-3~.
36.0m. 2.16.1O3s. 2.16m. 130s. ca. 5.10-%.
or
26
'I 16.2d. 27, 51 1.4O.1O6s.) 16.4d. 1.42.104s. 5.6Gs. 29, 51
f 11.4d. '(
Actinon An
19.4j.r. 0.12.108~. 29 yr. 9.2.108s. 2i.3d. 2.36.1O6s.
6. 17.10-*d.-I 7.14.10-7~.-' 6.08.10-*d;-' 7,OG~lO-'s. O.177~.-~
9.7.10b. or
5.15.10-2yr.-1 1.63.10-%.-' 3.4,1O-*yr.-l 1.1.10%.-' 3.66.10-2d.-1 4.24,10-'~.-'
24a, 24b, 25
4.76m. 286s. 4.71m. 283s.
1
30
1.93.10-2m.-1 51.9m. 3.21.10-4~. 3.12,103s.
31
0.321m.-' 3.12m. 5.35.10-3~.-1 187s.
27
ca. 140s.-'
ca. 7.10-3s.
0.145m.-' 2.43,10-3~.-' 0.146m.-' 2.44.10-3~.-'
6.87m. 412s. 6.83m. 410s.
32
Actinium D AcD 207.016(?) Actinium lead 82 PbZo7 207
THORIUM FAMILY T
Thorium Th At. wt. At. no. P. no.
232.12 90 232
1.8.1010yr. 5.6.10''s.
x 4.0,10-l1yr.-l 1.2.10-'8s.-'
T
2.5.101°yr. 8.0.10"s.
Literature
33
2446
Vol. 53
I N T E R N A T I O N A L RADIUM-STANDARDS COMMISSION
THORIUM FAMILY (ConcludeJ) X
1
Mesothorium 1 MsThl
88
228 6.13h. Mesothorium 2 MsThp 2.21.104s. 89 228 1.90yr. Radiothorium RdTh ~.0.107~. 90 228 3.64d. Thorium X ThX 3.14.1Ws. 88 224 54.5s. Thoron Til 86 220 0.14s. Thorium A ThA 84 216 10.0h. Thorium B ThB 3.82.104s. 82 212 60.5,. Thorium C ThC 3.63.10 83 212 10-0s. Thorium C' ThC' or
