INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY INORGANIC CHEMISTRY DIVISION COMMISSION ON ATOMIC WEIGHTS AND ISOTOPIC ABUNDANCES * SUBCOMMITTEE FOR ISOTOPIC ABUNDANCE MEASUREMENTS ** ISOTOPIC COMPOSITIONS OF THE ELEMENTS 1997 Prepared for publication by K.J.R. ROSMAN 1 AND P.D.P. TAYLOR 2 1 Department of Applied Physics, Curtin University of Technology, GPO Box U1987, Perth 6001, Australia. 2 Institute for Reference Materials and Measurements, European Commission-JRC, B-2440 Geel, Belgium. * Membership of the Commission for the period 1996D1997 was as follows: L. Schultz ( F RG , Chair m an) ; R. D . V ocke, Jr .( U S A , Secretar y) ; J. K . B?hlke (U S A , A ss ociate) ; H . J . D ietze ( F RG, A s s ociate) ; T. D ing ( China, A s sociate), M . Ebihar a ( J apan, Titular ) ; J . W. G r amlich (U S A , As s ociate) ; A . N. H alliday ( US A , A s sociate), H . R. K r ouse ( Canada, Titular ) ; H .K K luge ( FRG , A s sociate); R. D. Los s ( A ustr alia, T itular ) ; G . I . Ramendik ( Rus s ia, Titular ) ; D. E. Richardson (USA, Associate); M . S ti?venar d ( F r ance, A ss ociate) ; P . D . P . Taylor ( Belgium, Titular ) ; J . R. de Laeter ( A ustr alia, N ational Repr es entative) ; P . D e Bi?vr e ( Belgium, N ational Repr es entative); Y . X iao ( China, N ational Repr esentative) ; M . S hima ( J apan, N ational R epr es entative); A . P ir es de M atos ( P or tugal, N ational Repr es entative) ; N . N . G r eenw ood ( U K , N ational Repr es entative); H . S . P eis er ( U S A , N ational Repr es entative) . ** Membership of the Subcommittee for Isotopic Abundance Measurements 1991-1997: P. D. P. Taylor (Belgium, Chairman 1995-97); R. D . Los s ( A us tralia, Secretary 1995-97); Members: P.De Bi?vre (Belgium) J C?sario (France) J R de Laeter (Australia) H J Dietze (FRG) M Ebihara (Japan) J W T. J. Murphy (USA), H . S. P eis er ( U S A) , D. E. Richardson (USA), D. J. Rokop (USA), E. R. Roth (France), K. J. R. Rosman (Australia), M . Shima ( Japan ), R. D. Vocke (USA). ISOTOPIC COMPOSITIONS OF THE ELEMENTS 1997 Abstract- The Commission?s Subcommittee for the Isotopic Composition of the Elements (SIAM) has carried out its biennial review of isotopic compositions, as determined by mass spectrometry and other relevant methods. This involves a critical evaluation of the published literature, element by element, and forms the basis of the Table of Isotopic Compositions of the Elements as Determined by Mass Spectrometry presented here. New guidelines have been used to arrive at the uncertainties on the isotopic abundances and there are numerous changes to the Table since it was last published in 1991. Atomic Weights calculated from this table are consistent with A r (E) values listed in the Table of Standard Atomic Weights 1997. INTRODUCTION Previous compilations of òThe isotopic compositions of the elementsó were published in 1983 (ref. 1), 1984 (ref. 2) and 1991 (ref. 3) for the purpose of yielding atomic weights consistent with the Commission's òTable of Standard Atomic Weights ó [4, 5, 6]. During the past six years the Commission, through its Subcommittee for Isotopic Abundance Measurements (SIAM), has continued to assemble and evaluate new data which has led to improvements to the tabulated isotopic composition of a number of elements. In 1993, the statistical guidelines for assigning uncertainties to the representative abundances were revised and extended by the Commission's Working Party on Statistical Evaluation of Isotopic Abundances (members: K. J. R. Rosman (Chairman), P. De Bi?vre and J. W. Gramlich). All the data presented in the Table were reassessed according to these guidelines. The present table was assembled for publication following the meeting of SIAM held at Kloster Seeon (Germany), just prior to the 39th IUPAC General Assembly held at Geneva (Switzerland) in 1997 and is presented here as a companion paper to the Atomic Weights of the Elements 1997. REFERENCES 1. N.E. Holden, R.L. Martin and I.L. Barnes, Pure Appl. Chem., 55, 1119-1136 (1983). 2. N.E. Holden, R.L. Martin and I.L. Barnes, Pure Appl. Chem., 56, 675-694 (1984). 3. IUPAC Commission on Atomic Weights and Isotopic Abundances, Pure Appl. Chem. 63, 991-1002 (1991). 4. IUPAC Commission on Atomic Weights and Isotopic Abundances, Pure Appl. Chem. 55, 1101-1118 (1983). 5. IUPAC Commission on Atomic Weights and Isotopic Abundances, Pure Appl. Chem. 56, 653-674 (1984). 6. IUPAC Commission on Atomic Weights and Isotopic Abundances, Pure Appl. Chem. 63, 975-990 (1991). THE TABLE OF ISOTOPIC COMPOSITIONS OF THE ELEMENTS AS DETERMINED BY MASS SPECTROMETRY The Subcommittee for Isotopic Abundance Measurements (SIAM) has examined the literature available to it through July l997 and has evaluated these data to produce a table of recommended isotopic abundances for the elements. The table is intended to include values for normal terrestrial samples and does not include values published for meteoritic or other extra-terrestrial materials. The column contents are as follows: Column l: The elements are tabulated in ascending order of their atomic numbers. Column 2: The symbols for the elements are listed using the abbreviations recommended by IUPAC. Column 3: The mass number for each isotope is listed. Column 4: Range of natural variations. Given are the highest and lowest abundances published for each isotope from measurements which have been accepted by the Subcommittee. No data are given in this Column unless a range has been reliably established. The limits given do not include certain exceptional samples, these are noted with a "g" in Column 5. Column 5: Annotations The letters appended in this Column have the following significance: g geologically exceptional specimens are known in which the element has an isotopic composition outside the reported range. (refers to column 4) m modified isotopic compositions may be found in commercially available material because it has been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations from the isotopic compositions given can occur. (refers to column 9) r range in isotopic composition existing in normal terrestrial material limits the precision of the isotopic abundances. (refers to column 9) Column 6: The best measurement from a single terrestrial source. The values are reproduced from the original literature. The uncertainties on the last digits are given in parenthesis as reported in the original publication. As they are not reported in any uniform manner in the literature, SIAM indicates this as follows: ls, 2s, 3s indicates l, 2, or 3 standard deviations, P indicates some other error as defined by the author, and ￠se￠ indicates standard error (standard deviation of the mean). Where data are published as isotopic ratios, they, including their uncertainties, are converted to abundances using orthodox procedures. "C" is appended when calibrated mixtures have been used to correct the mass spectrometer for bias, giving an "absolute" result within the errors stated in the original publication. "L" is appended when the linearity of the mass spectrometer has been established for the relevant abundance ratios by using synthetic mixtures of isotopes or certified materials produced by an appropriate Standards laboratory. "N" is appended when none of the above requirements are met. The user is cautioned that: a) Since the data are reproduced from the literature, the sum of the isotopic abundances may not equal l00 percent. b) When a range of compositions has been established, the samples used for the best measurement may come from any part of the range. c) An uncalibrated "Best Measurement" is not necessarily free of systematic errors. Column 7: The reference shown is that from which the data shown in column 6 were taken (Appendix A). Column 8: Reference materials or samples with normal terrestrial isotopic values which are known to be available are listed. An asterisk indicates the reference material used for the best measurement. When additional reference materials are available, the distributors are listed in lieu of specific reference materials (Appendix B). Column 9: Representative Isotopic Composition. In this column are listed the values which, in the opinion of SIAM, represent the isotopic composition of the chemicals and/or materials most commonly encountered in the laboratory. They may not, therefore, correspond to the most abundant natural material. For example, in the case of hydrogen, the deuterium abundance quoted corresponds to that in fresh water in temperate climates rather than to ocean water. The uncertainties listed in parenthesis cover the range of probable variations of the materials as well as experimental errors. The number of significant figures is chosen to be consistent with the uncertainties, which in turn are derived by applying the statistical guidelines SIAM uses for assigning uncertainties to published isotope abundance measurements. An Atomic Weight calculated from these abundances will be consistent with A r (E) values listed in the Table of Standard Atomic Weights 1997. Warning 1) Values in column 9 should be used to determine the average properties of material of unspecified natural terrestrial origin, though no actual sample having the exact composition listed may be available. 2) When precise work is to be undertaken, such as assessment of individual properties, samples with more precisely known isotopic abundances (such as those listed in column 8) should be obtained or suitable measurements should be made. TABLE 1. Isotopic compositions of the elements as determined by mass spectrometry Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot-Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 1 H 1 99.9816 - 99.9975 m,r 99.984426 (5) 2s C 70HAG1 VSMOW* 99.9885 (70) 2 0.0184 - 0.0025 0.015574 (5) CEA 0.0115 (70) b IAEA (in water) NIST 2He34.6x10 -8 -0.0041 g,r 0.0001343(13) 1s C 88SAN1 Air* 0.000137 (3) 4 100 - 99.9959 99.9998657 (13) 99.999863 (3) (in air) 3Li67.21 - 7.71 m,r 7.589 (24) 2s C 97QI1 IRMM-016* [7.59(4)] c 7 92.79 - 92.29 92.411 (24) IAEA [92.41(4)] IRMM NIST 4 Be 9 100 63LEI1 100 5B1018.927 - 20.337 m,r 19.82 (2) 2s C 69BIE1 IRMM-011* 19.9 (7) 11 81.073- 79.663 80.18 (2) NIST 80.1 (7) 6 C 12 98.85 - 99.02 r 98.8922 (28) P C 90CHA1 NBS19* 98.93 (8) 13 1.15 - 0.98 1.1078 (28) IAEA 1.07 (8) NIST 7 N 14 99.890 -99.652 r 99.6337 (4) P C 58JUN1 Air* 99.632 (7) d 15 0.411 - 0.348 0.3663 (4) IAEA 0.368 (7) NIST 8O1699.7384 -99.7756 r 99.7628 (5) 1s N 76BAEl VSMOW* 99.757 (16) 17 0.0399 - 0.0367 0.0372 (4) e 88LI1 IAEA 0.038 (1) 18 0.2217 - 0.1877 0.20004 (5) NIST 0.205 (14) 9 F 19 100 20AST1 100 10 Ne 20 90.514 - 88.47 g,m 90.4838 (90) 1s C 84BOT1 Air* 90.48 (3) 21 1.71 - 0.266 r 0.2696 (5) 0.27 (1) 22 9.96 - 9.20 9.2465 (90) 9.25 (3) (in air) 11 Na 23 100 56WHI1 100 12 Mg 24 78.992 (25) 2s C 66CAT1 NIST-SRM980* 78.99 (4) 25 10.003 (9) 10.00 (1) 26 11.005 (19) 11.01 (3) 13 Al 27 100 56WHI1 100 Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot-Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 14 Si 28 92.21 - 92.25 r 92.22968 (44) 2s C 97GON1 IAEA 92.2297 (7) 29 4.69 - 4.67 4.68316 (32) IRMM 4.6832 (5) 30 3.10 - 3.08 3.08716 (48) NIST 3.0872 (5) 15 P 31 100 63LEI1 100 16 S 32 94.537 - 95.261 r 95.018 (4) P C 50MAC1 CEA 94.93 (31) 33 0.787 - 0.731 0.750 (7) IAEA 0.76 (2) 34 4.655 - 3.993 4.215 (4) NIST 4.29 (28) 36 0.021 -0.015 0.017 (2) 0.02 (1) 17 Cl 35 75.64 - 75.86 m 75.771 (45) 2s C 62SHI1 NIST-SRM975 * 75.78 (4) 37 24.36 - 24.14 24.229 (45) 24.22 (4) 18 Ar 36 g 0.3365 (6) P C 50NIE1 Air* 0.3365 (30) 38 0.0632 (1) 0.0632 (5) 40 99.6003 (6) 99.6003 (30) (in air) 19 K 39 93.25811 (292) 2s C 75GAR1 NIST-SRM985* 93.2581 (44) 40 0.011672 (41) 0.0117 (1) 41 6.73022 (292) 6.7302 (44) 20 Ca 40 96.982 - 96.880 g,r 96.941 (6) 2s N 72MOO1 NIST-SRM915* 96.941 (156) h 42 0.656 - 0.640 0.647 (3) 0.647 (23) 43 0.146 - 0.131 0.135 (2) 0.135 (10) 44 2.130 - 2.057 2.086 (4) 2.086 (110) 46 0.0046 - 0.0031 0.004 (1) 0.004 (3) 48 0.200 - 0.179 0.187 (1) 0.187 (21) 2l Sc 45 100 50LEL1 100 22 Ti 46 8.249 (21) 2s C 93SHI1 8.25 (3) 47 7.437 (14) 7.44 (2) 48 73.720 (22) 73.72 (3) 49 5.409 (10) 5.41 (2) 50 5.185 (13) 5.18 (2) 23 V 50 0.2502 - 0.2487 g 0.2497 (6) 1s F 66FLE1 0.250 (4) 51 99.7513 - 99.7498 99.7503 (6) 99.750 (4) 24 Cr 50 4.3452 (85) 2s C 66SHI1 NIST-SRM979* 4.345 (13) 52 83.7895 (117) 83.789 (18) 53 9.5006 (110) 9.501 (17) 54 2.3647 (48) 2.365 (7) Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot-Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 25 Mn 55 100 63LEI1 100 26 Fe 54 5.845(23) 2s C 92TAY1 IRMM-014* 5.845 (35) 56 91.754(24) 91.754 (36) 57 2.1191(65) 2.119 (10) 58 0.2819(27) 0.282 (4) 27 Co 59 100 63LEI1 100 28 Ni 58 68.0769 (59) 2s C 89GRA1 68.0769 (89) 60 26.2231 (51) 26.2231 (77) 61 1.1399 (4) 1.1399 (6) 62 3.6345 (11) 3.6345 (17) 64 0.9256 (6) 0.9256 (9) 29 Cu 63 69.24 - 68.98 r 69.174 (20) 2s C 64SHI1 NIST-SRM976* 69.17 (3) 65 31.02 - 30.76 30.826 (20) 30.83 (3) 30 Zn 64 48.63 (20) 2s F 72ROS1 48.63 (60) 66 27.90 (9) 27.90 (27) 67 4.10 (4) 4.10 (13) 68 18.75 (17) 18.75 (51) 70 0.62 (1) 0.62 (3) 31 Ga 69 m 60.1079 (62) 2s C 86MAC1 NIST-SRM994* 60.108 (9) 71 39.8921 (62) 39.892 (9) 32 Ge 70 21.234 (31) 1s L 86GRE1 20.84 (87) k 72 27.662 (29) 27.54 (34) 73 7.717 (5) 7.73 (5) 74 35.943 (25) 36.28 (73) 76 7.444 (14) 7.61 (38) 33 As 75 100 63LEI1 100 34 Se 74 r 0.889 (3) 1s N 89WAC1 0.89 (4) 76 9.366 (18) 9.37 (29) 77 7.635 (10) 7.63 (16) 78 23.772 (20) 23.77 (28) 80 49.607 (17) 49.61 (41) 82 8.731 (10) 8.73 (22) 35 Br 79 50.686 (26) 2s C 64CAT1 NIST-SRM977* 50.69 (7) 81 49.314 (26) 49.31 (7) 36 Kr 78 g,m 0.35351 (7) 2s N 94VAL1 0.35 (1) 80 2.28086(29) 2.28 (6) 82 11.58304 (76) 11.58 (14) 83 11.49533 (35) 11.49 (6) 84 56.98890 (62) 57.00 (4) 86 17.29835(26) 17.30 (22) (in air) Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot-Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 37 Rb 85 g 72.1654 (132) 2s C 69CAT1 NIST-SRM984 72.17 (2) 87 27.8346 (132) 27.83 (2) 38 Sr 84 0.58 - 0.55 g,r 0.5574 (16) 2s C 82MOO1 NIST-SRM 987* 0.56 (1) 86 9.99 - 9.75 9.8566 (34) NIST 9.86 (1) 87 7.14 - 6.94 7.0015 (26) 7.00 (1) h 88 82.75 - 82.29 82.5845 (66) 82.58 (1) 39 Y 89 100 57COL1 100 40 Zr 90 g 51.452 (9) 2s N 83NOM1 51.45 (40) 91 11.223 (12) 11.22 (5) 92 17.146 (7) 17.15 (8) 94 17.380 (12) 17.38 (28) 96 2.799 (5) 2.80 (9) 41 Nb 93 100 56WHI1 100 42 Mo 92 g 14.8362 (148) 2s N 74MOO1 14.84 (35) 94 9.2466 (92) 9.25 (12) 95 15.9201 (159) 15.92 (13) 96 16.6756 (167) 16.68 (2) 97 9.5551 (96) 9.55 (8) 98 24.1329 (241) 24.13 (31) 100 9.6335 (96) 9.63 (23) 43 Tc -- --- ------ 44 Ru 96 g 5.5420 (1) 1s N 97HUA1 5.54 (14) 98 1.8688 (2) 1.87 (3) 99 12.7579 (6) 12.76 (14) 100 12.5985 (4) 12.60 (7) 101 17.0600 (10) 17.06 (2) 102 31.5519 (11) 31.55 (14) 104 18.6210 (11) 18.62 (27) 45 Rh 103 100 63LEI1 100 46 Pd 102 g,r 1.020 (8) 2s C 78SHI1 1.02 (1) 104 11.14 (5) 11.14 (8) 105 22.33 (5) 22.33 (8) 106 27.33 (2) 27.33 (3) 108 26.46 (6) 26.46 (9) 110 11.72 (6) 11.72 (9) 47 Ag 107 g 51.8392 (51) 2s C 82POW1 NIST-SRM978* 51.839 (8) 109 48.1608 (51) 48.161 (8) Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot-Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 48 Cd 106 g 1.25 (2) 2s F 80ROS1 1.25 (6) 108 0.89 (1) 0.89 (3) 110 12.49 (6) 12.49 (18) 111 12.80 (4) 12.80 (12) 112 24.13 (7) 24.13 (21) 113 12.22 (4) 12.22 (12) 114 28.73 (14) 28.73 (42) 116 7.49 (6) 7.49 (18) 49 In 113 g 4.288 (5) 2s N 91CHA1 4.29 (5) 115 95.712 (5) 95.71 (5) 50 Sn 112 g 0.973 (3) 1s C 83DEV1 0.97 (1) 114 0.659 (3) f 84ROS1 0.66 (1) 115 0.339 (3) f 0.34 (1) 116 14.536 (31) 14.54 (9) 117 7.676 (22) 7.68 (7) 118 24.223 (30) 24.22 (9) 119 8.585 (13) 8.59 (4) 120 32.593 (20) 32.58 (9) 122 4.629 (9) 4.63 (3) l24 5.789 (17) 5.79 (5) 51 Sb 121 g 57.213 (32) 2s C 93CHA1 57.21 (5) 123 42.787 (32) 42.79 (5) 52 Te 120 g 0.096 (1) 2se N 78SMI1 0.09 (1) k 122 2.603 (1) 2.55 (12) 123 0.908 (1) 0.89 (3) 124 4.816 (2) 4.74 (14) 125 7.139 (2) 7.07 (15) 126 18.952 (4) 18.84 (25) 128 31.687 (4) 31.74 (8) 130 33.799 (3) 34.08 (62) 53 I 127 100 49LEL1 100 54 Xe 124 g,m 0.08913(3) 2s N 94VAL1 0.09 (1) 126 0.08880 (2) 0.09 (1) 128 1.91732 (12) 1.92 (3) 129 26.43964 (17) 26.44 (24) 130 4.08271 (15) 4.08 (2) 131 21.17961 (19) 21.18 (3) 132 26.89157 (11) 26.89 (6) 134 10.44232 (17) 10.44 (10) 136 8.86890 (14) 8.87 (16) 55 Cs 133 100 56WHI1 100 Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot-Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 56 Ba 130 g 0.1058 (2) 3se F 69EUG1 0.106 (1) 132 0.1012 (2) 0.101 (1) 134 2.417 (3) 2.417 (18) 135 6.592 (2) 6.592 (12) 136 7.853 (4) 7.854 (24) 137 11.232 (4) 11.232 (24) 138 71.699 (7) 71.698 (42) 57 La 138 g 0.09017 (5) 2se N 87MAK1 0.090 (1) 139 99.90983 (5) 99.910 (1) 58 Ce 136 0.186 -0.185 g 0.186 (1) 2s C 95CHA1 0.185 (2) 138 0.254 - 0 251 0.251 (1) 0.251 (2) h 140 88.449 - 88.446 88.449 (34) 88.450 (51) 142 11.114 - 11.114 11.114 (34) 11.114 (51) 59 Pr 141 100 57COL1 100 60 Nd 142 27.30 - 26.80 g 27.16 (4) 2se N 81HOL1 27.2 (5) 143 12.32 - 12.12 12.18 (2) 12.2 (2) h 144 23.97 - 23.795 23.83 (4) 23.8 (3) 145 8.35 - 8.23 8.30 (2) 8.3 (1) 146 17.35 - 17.06 17.17 (3) 17.2 (3) 148 5.78 - 5.66 5.74 (1) 5.7 (1) 150 5.69 - 5.53 5.62 (1) 5.6 (2) 6l Pm --- --- 62 Sm 144 g 3.0734 (9) 2s F 97CHA1 3.07 (7) 147 14.9934 (18) 14.99 (18) 148 11.2406 (15) 11.24 (10) 149 13.8189 (18) 13.82 (7) 150 7.3796 (14) 7.38 (1) 152 26.7421 (66) 26.75 (16) 154 22.7520 (68) 22.75 (29) 63 Eu 151 g 47.810 (42) 2se C 94CHA1 47.81 (3) 153 52.190 (42) 52.19 (3) 64 Gd 152 g 0.2029 (4) 2se N 70EUG1 0.20 (1) 154 2.1809 (4) 2.18 (3) 155 14.7998 (17) 14.80 (12) 156 20.4664 (6) 20.47 (9) 157 15.6518 (9) 15.65 (2) 158 24.8347 (16) 24.84 (7) 160 21.8635 (7) 21.86 (19) 65 Tb 159 100 57COL1 100 Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot-Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 66 Dy 156 g 0.056 (1) 2se N 81HOL1 0.06 (1) 158 0.096 (2) 0.10 (1) 160 2.34 (2) 2.34 (8) 161 18.91 (5) 18.91 (24) 162 25.51 (7) 25.51 (26) 163 24.90 (7) 24.90 (16) 164 28.19 (8) 28.18 (37) 67 Ho 165 100 57COLl 100 68 Er 162 g 0.137 (1) 2se N 81HOL1 0.14 (1) 164 1.609 (5) 1.61 (3) 166 33.61 (7) 33.61 (35) 167 22.93 (5) 22.93 (17) 168 26.79 (7) 26.78 (26) 170 14.93 (5) 14.93 (27) 69 Tm 169 100 57COL1 100 70 Yb 168 g 0.127 (2) 2se N 81HOL1 0.13 (1) 170 3.04 (2) 3.04 (15) 171 14.28 (8) 14.28 (57) 172 21.83 (l0) 21.83 (67) 173 16.13 (7) 16.13 (27) 174 31.83 (14) 31.83 (92) 176 12.76 (5) 12.76 (41) 71 Lu 175 g 97.416 (5) 2se N 83PAT1 97.41 (2) 176 2.584 (5) 2.59 (2) 72 Hf 174 0.1621 - 0.1619 0.1620 (9) 2se N 83PAT1 0.16 (1) 176 5.271 - 5.206 5.2604 (56) 5.26 (7) h 177 18.606 - 18.593 18.5953 (12) 18.60 (9) 178 27.297 - 27.278 27.2811 (22) 27.28 (7) 179 13.630 - 13.619 13.6210 (9) 13.62 (2) 180 35.100 - 35.076 35.0802 (26) 35.08 (16) 73 Ta 180 0.0123 (3) 1se N 56WHI1 0.012 (2) 181 99.9877 (3) 99.988 (2) 74 W 180 0.1198 (2) 1s N 91V?L2 0.12 (1) 182 26.4985 (49) 26.50 (16) 183 14.3136 (6) 14.31 (4) 184 30.6422 (13) 30.64 (2) 186 28.4259 (62) 28.43 (19) 75 Re 185 37.398 (16) 2s C 73GRA1 NIST-SRM989* 37.40 (2) 187 62.602 (16) 62.60 (2) Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot- Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 76 Os 184 g,r 0.0197 (5) 1s N 91V?L1 0.02 (1) 186 1.5859 (44) 1.59 (3) 187 1.9644 (12) 1.96 (2) h 188 13.2434 (19) 13.24 (8) 189 16.1466 (16) l6.l5 (5) 190 26.2584 (14) 26.26 (2) 192 40.7815 (22) 40.78 (19) 77 Ir 191 37.272 (15) 1s N 93WAL1 37.3 (2) 193 62.728 (15) 62.7 (2) 78 Pt 190 0.013634 (68) 1s N 96TAY1 0.014 (1) 192 0.782659 (35) 0.782 (7) 194 32.96700 (77) 32.967 (99) 195 33.831557 (42) 33.832 (10) 196 25.24166 (36) 25.242 (41) 198 7.16349 (42) 7.163 (55) 79 Au 197 100 63LEI1 100 80 Hg 196 0.15344(19) 1s N 89ZAD1 0.15 (1) 198 9.968 (13) 9.97 (20) 199 16.873 (17) 16.87 (22) 200 23.096 (26) 23.10 (19) 201 13.181 (13) 13.18 (9) 202 29.863 (33) 29.86 (26) 204 6.865 (7) 6.87 (15) 81 Tl 203 29.524 (9) 2s C 80DUN1 NIST-SRM997* 29.524 (14) 205 70.476 (9) 70.476 (14) 82 Pb 204 1.65 - 1.04 g,r 1.4245 (12) 2s C 68CAT1 NIST-SRM98l* 1.4 (1) 206 27.48 - 20.84 24.1447 (57) NIST 24.1 (1) h 207 23.65 - 17.62 22.0827 (27) 22.1 (1) h 208 56.21 - 51.28 52.3481 (86) 52.4 (1) h 83 Bi 209 100 63LEI1 100 84 Po 85 At 86 Rn 87 Fr 88 Ra 89 Ac Best Range of Measurement Available Representaive Natural from a Single Reference Isotopic Atomic Mass Variations Annot-Terrestrial Source Reference Materials a Composition Number Symbol Number (Atom %) ations (Atom %) (App. A) (App. B) (Atom %) 12 3 4 5 6 7 8 9 90 Th 232 g 100 36DEM1 100 91 Pa 231 100 77BRO1 100 92 U 234 0.0059 - 0.0050 g,m 0.00548 (2) i 1s N 69SMI1 IRMM-184 [0.0055(2)] 235 0.7202 - 0.7198 r 0.7200 (1) 76COW1 CEA [0.7200(51)] c,h 238 99.2752 - 99.2739 99.2745 (10) IRMM [99.2745(106)] NBL *Reference material used for the best measurement. a NIST materials were previously labelled NBS. IRMM materials were previously labelled CBNM. b The range of 2 H in tank hydrogen is 0.0032 to 0.0184 atom percent. c Materials depleted in 6 Li and 235 U are commercial sources of laboratory shelf reagents. In the case of Li such samples are known to have 6 Li abundances in the range 2.007-7.672 atom percent, with natural materials at the higher end of this range. d The Commission recommends that the value of 272 be employed for 14 N/ 15 N of N 2 in air for the calculation of atom percent 15 N from measured d 15 N values. e The reference reported a calibrated 16 O/ 18 O ratio on VSMOW; 17 O abundance was derived from 88LI1. f Due to 115 In contamination and an error in the 114 Sn abundance the 115 Sn and 114 Sn abundances reported by 83DEV1 were adjusted using data from 84ROS1. g Not used since g is used in column 5. h Evaluated isotopic composition is for most but not all commercial samples. i The 234 U abundance is from 69SMI1, 235 U and 238 U are from 76COW1. k An electron multiplier was used for these measurements and the measured abundances were adjusted the using a square root of the masses. APPENDIX A: REFERENCES FOR TABLE 1 20AST1 F. W. Aston, Phil. Mag. 40, 628-634 (1920). The Mass Spectra of Chemical Elements. 36DEM1 A. J. Dempster, Nature 136, 120 (1936). Atomic Masses of Uranium and Thorium. 49LEL1 W. T. Leland, Phys. Rev. 76, 992 (1949). On the Abundance of 129 I, 118 Te and 190 Pt. 50LEL1 W. T. Leland, Phys. Rev. 77, 634-640 (1950). The Isotopic Composition of Scandium, Gadolinium, and Dysprosium. 50MAC1 J. MacNamara, and H. G. Thode, Phys. Rev. 78, 307-308 (1950). Comparison of the Isotopic Constitution of Terrestrial and Meteoritic Sulphur. 50NIE1 A. O. Nier, Phys. Rev. 77, 789-793 (1950). A Redetermination of the Relative Abundances of the Isotopes of Carbon, Nitrogen, Oxygen, Argon and Potassium. 56WHI1 F. A. White, T. L. Collins, Jr., and F. M. Rourke, Phys. Rev. 101, 1786-1791 (1956). Search for Possible Naturally Occurring Isotopes of Low Abundance. 57COL1 T. L. Collins, Jr., F. M. Rourke, and F. A. White, Phys. Rev. 105, 196-197 (1957). Mass Spectrometric Investigation of the Rare Earth Elements for the Existence of New Stable Isotopes. 58JUN1 G. Junk, and H. J. Svec, Geochim. Cosmochim. Acta 14, 234-243 (1958). The Absolute Abundance of the Nitrogen Isotopes in the Atmosphere and Compressed Gas from Various Sources. 62SHI1 W.R.Shields, T.J.Murphy, E.L.Garner, and V.H.Dibeler, J.Am. Chem. Soc. 84, 1519-1522 (1962). Absolute Isotopic Abundance Ratios and the Atomic Weight of Chlorine. 63LEI1 F. D. Leipziger, Appl. Spec. 17, 158-160 (1963). Some New Upper Limits of Isotopic Abundance by Mass Spectrometry. 64CAT1 E. J. Catanzaro, T. J. Murphy, E. L. Garner, and W. R. Shields, J. Res. Nat. Bur., Stand. (U.S.),68A, 593-599 (1964). Absolute Isotopic Abundance Ratio and the Atomic Weight of Bromine. 64SHI1 W.R. Shields, T.J. Murphy, and E.L. Garner, J.Res. Nat. Bur. Stand. (U.S.), 68A, 589-592 (1964). Absolute Isotopic Abundance Ratios and the Atomic Weight of a Reference Sample of Copper. 66CAT1 E. J. Catanzaro, T. J. Murphy, E. L. Garner, and W. R. Shields, J. Res. Nat. Bur. Stand. (U.S.),70A, 453-458 (1966). Absolute Isotopic Abundance Ratios and the Atomic Weight of Magnesium. 66FLE1 G. D. Flesch,J. Capellen, and H. J. Svec, Adv. Mass Spectrom. III, 571-581, (1966), Leiden and Son, London. The Abundance of the Vanadium Isotopes from Sources of Geochemical Interest. 66SHI1 W. R. Shields, T. J. Murphy, E. J. Catanzaro, and E. L. Garner, J. Res. Nat. Bur. Stand. (U.S.), 70A, 193-197 (1966). Absolute Isotopic Abundance Ratios and the Atomic Weight of a Reference Sample of Chromium. 68CAT1 E. J. Catanzaro, T. J. Murphy, W. R. Shields, and E. L. Garner, J. Res. Nat. Bur. Stand. (U.S.), 72A, 261-266 (1968). Absolute Isotopic Abundance Ratios of Common, Equal-Atom, and Radiogenic Lead Isotopic Standards. 69BIE1 P. J. De Bievre, and G. H. Debus, Int. J. Mass Spectrom. Ion Phys. 2, 15-23 (1969). Absolute Isotope Ratio Determination of a Natural Boron Standard. 69CAT1 E. J. Catanzaro, T. J. Murphy, E. L. Garner, and W. R. Shields, J. Res. Nat. Bur. Stand. (U.S.),73A, 511-516(1969). Absolute Isotopic Abundance Ratios and the Atomic Weight of Terrestrial Rubidium. 69EUG1 O. Eugster, F. Tera, and G. J. Wasserburg, J. Geophys. Res. 74, 3897-3908 (1969). Isotopic Analyses of Barium in Meteorites and in Terrestrial Samples. 69SMI1 R. F. Smith, and J. M. Jackson, U. S. Atomic Energy Commission Report KY-581 (1969). Variations in U-234 Concentration of Natural Uranium. 70EUG1 O. Eugster, F. Tera, D. S. Burnett, and G. J. Wasserburg, J. Geophys. Res. 75, 2753-2768 (1970). Isotopic Composition of Gadolinium and Neutron-capture Effects in Some Meteorites. 70HAG1 R. Hagemann, G. Nief, and E. Roth, Tellus 22, 712-715 (1970). Absolute Isotopic Scale for Deuterium Analysis of Natural Waters, Absolute D/H Ratio for SMOW. 72MOO1 L. J. Moore, and L. A. Machlan, Anal. Chem. 44, 2291-2296 (1972). High Accuracy Determination of Calcium in Blood Serum by Isotope Dilution Mass Spectrometry. 72ROS1 K. J. R. Rosman, Geochim. Cosmochim. Acta 36, 801-819 (1972). A Survey of the Isotopic and Elemental Abundance of Zinc. 73GRA1 J. W. Gramlich, T. J. Murphy, E. L. Garner, and W. R. Shields, J. Res. Nat. Bur. Stand. (U.S.), 77A, 691-698 (1973). Absolute Isotopic Abundance Ratio and Atomic Weight of a Reference Sample of Rhenium. 74MOO1 L. J. Moore, L. A. Machlan, W. R. Shields, and E. L. Garner, Anal. Chem. 46, 1082-1089 (1974). Internal Normalization Techniques for High Accuracy Isotope Dilution Analyses : Application to Molybdenum and Nickel in Standard Reference Materials. 75GAR1 E. L. Garner, T. J. Murphy, J. W. Gramlich, P. J. Paulsen, and I. L. Barnes, J. Res. Nat. Bur. Stand.(U.S.), 79A, 713-725 (1975). Absolute Abundance Ratios and the Atomic Weight of a Reference Sample of Potassium. 76BAE1 P. Baertschi, Earth Planet. Sci. Lett., 31, 341-344 (1976). Absolute 18 0 Content of Standard Mean Ocean Water. 76COW1 G. A. Cowan, and H. H. Adler, Geochim. Cosmochim. Acta, 40, 1487-1490 (1976). The Variability of the Natural Abundance of U-235. 76DEV1 C. Devillers, T. Lecomte, M. Lucas, and R. Hagemann, Proc. 7th Int. Mass Spectrom. Conf. Florence, 553-564 (1976). Mass Spectrometric Investigations on Ruthenium Isotopic Abundances. 77BRO1 D. Brown, Gmelin Handbuch der Anorg. Chem., 8th ed., Syst.51, Erg.-Bd. 1, 6, Springer (1977). Occurrence of Protactinium Isotopes in Nature and Synthesis of Weighable Amounts in Nuclear Reactions. 78SHI1 M. Shima, C. E. Rees, and H. G. Thode, Can. J. Phys., 56, 1333-1339 (1978). The Isotopic Composition and Atomic Weight of Palladium. 78SMI1 C.L. Smith, K.J.R. Rosman, and J.R.De Laeter, Int. J. Mass Spectrom. Ion Phys., 28, 7-17 (1978). The Isotopic Composition of Tellurium. 80DUN1 L. P. Dunstan, J. W. Gramlich, I. L. Barnes, and W. C. Purdy, J. Res. Nat. Bur. Stand. (U.S.), 85, 1-10 (1980). The Absolute Isotopic Abundance and the Atomic Weight of a Reference Sample of Thallium. 80ROS1 K.J.R. Rosman, I.L. Barnes, L.J. Moore, and J.W. Gramlich, Geochemical J., 14, 269-277 (1980). Isotope Composition of Cd, Ca, and Mg in the Brownfield Chrondrite. 81HOL1 P. Holliger and C. Devillers, Earth Planet. Sci. Lett., 52, 76-84 (1981). Contribution a l' etude de la temperature dans les reacteurs fossiles d' Oklo par la mesure du rapport isotopique du Lutetium. 82MOO1 L.J.Moore, T.J.Murphy, I.L.Barnes, and P.J.Paulsen, J.Res. Nat. Bur. Stand. (U.S.),87,1-8 (1982). Absolute Isotopic Abundance Ratios and Atomic Weight of a Reference Sample of Strontium. The Absolute Isotopic Abundance and Atomic Weight of a Reference Sample of Silver. 83DEV1 C. Devillers, T. Lecomte, and R. Hagemann, Int.J. Mass Spectrom. Ion Phys. 50, 205-217 (1983). Absolute Isotope Abundances of Tin. 83NOM1 M. Nomura, K. Kogure, and M. Okamoto, Int. J. Mass Spectrom. Ion Phys., 50, 219-227 (1983). Isotopic Abundance Ratios and Atomic Weight of Zirconium. 83MIC1 E. Michiels, and P. De Bievre, Int. J. Mass Spectrom. Ion Phys., 49, 265-274 (1983). Absolute Isotopic Composition and the Atomic Weight of a Natural Sample of Lithium. 83PAT1 P. J. Patchett, Geochim. Cosmochim. Acta 47, 81-91 (1983). Importance of the Lu-Hf Isotopic System in Studies of Planetary Chronology and Chemical Evolution. 84BOT1 D.J. Bottomley, J.D. Ross, and W.B. Clarke, Geochim. Cosmochim. Acta, 48, 1973-1985 (1984). Helium and Neon Isotope Geochemistry of some Ground Waters from the Canadian Precambrian Shield. 84ROS1 K.J.R.Rosman, R.D.Loss, and J.R. DeLaeter, Int.J.Mass Spectrom. Ion Proc.,56, 281-291 (1984). The Isotopic Composition of Tin. 86GRE1 M.D.Green, K.J.R.Rosman, and J.R.DeLaeter, Int. J. Mass Spectrom. Ion Proc., 68, 15-24 (1986). The Isotopic Composition of Germanium in Terrestrial Samples. 86MAC1 L.A. Machlan, J.W. Gramlich, L.J. Powell, and G.M. Lambert, J. Res. Nat. Bur. Stand. (U.S.), 91, 323-331 (1986). Absolute Isotopic Abundance Ratio and Atomic Weight of a Reference Sample of Gallium. 87MAK1 A. Makishima, H. Shimizu, and A. Masuda, Mass Spectroscopy, 35, 64-72 (1987). Precise Measurement of Cerium and Lanthanum Isotope Ratios. 88LI1 W. Li, D. Jin, and T.L. Chang, Kexue Tinboa, 33, 1610-1613 (1988). Measurement of the absolute abundance of oxygen-17 in V-SMOW. 88SAN1 Y. Sano, H. Wakita, and X. Sheng, Geochem. J., 22, 177-181 (1988). Atmospheric Helium Isotope Ratio. 89GRA1 J.W. Gramlich, L.A. Machlan, I.L. Barnes, and P.J. Paulsen, J. Res. Natl. Inst. Stand. Technol.(U.S.), 94, 347-356 (1989). The Absolute Abundance Ratios and Atomic Weight of a Reference Sample of Nickel. 89WAC1 M. Wachsmann, and K. G. Heumann, Adv. Mass Spectrom., 11B, 1828-1829 (1989). 89ZAD1 M.G. Zadnik, S. Specht, and F. Begemann, Int. J. Mass Spectrom. Ion Proc., 89, 103-110 (1989). Revised Isotopic Composition of Terrestrial Mercury. 90CHA1 T.L.Chang, and W. Li, Chin. Sci. Bull., 35 , 290-296 (1990). A Calibrated Measurement of the Atomic Weight of Carbon. 91CHA1 T.L.Chang, Y.K. Xiao, Chin. Chem. Letters, 2, 407-410 (1991). The Atomic Weight of Indium. 91VOL1 J. Volkening, T. Walzyck, and K.G.. Heumann, Int. J. Mass Spectrom. Ion Proc.,105, 147- 159 (1991). Osmium Isotope ratio Determinations by Negative Thermal Ionisation Mass Spectrometry. 91VOL2 J. Volkening, M. Koppe, and K. Heumann, Int.J.Mass. Spectrom. Ion Proc., 107, 147-159 (1991). Tungsten Isotope Ratio Measurements by Negative Thermal Ionisation Mass Spectrometry. 92TAY1 P.D.P. Taylor, R. Maeck, and P. De Bievre, Int. J. Mass Spectrom. Ion Proc., 121, 111-125 (1992). Determination of the Absolute Isotopic Composition and Atomic Weight of a Reference Sample of Natural Iron. 93CHA1 T.L.Chang, Q.Y.Qian, M.T.Zhao, and J.Wang, Int.J. Mass Spectrom. Ion Proc.,123, 77-82 (1993). The Isotopic Abundance of Antimony. 93SHI1 M. Shima, and N. Torigoye, Int. J. Mass Spectrom. Ion Proc., 123, 29-39 (1993). The Isotopic Composition and Atomic Weight of Titanium. 93WAL1 T. Walczyk, and K.G. Heumann, Int. J. Mass Spectrom. Ion Proc., 123, 139-147 (1993). Iridium Isotope Ratio Measurements by Negative Thermal Ionisation Mass Spectrometry and Atomic Weight of Iridium. 94CHA1 T.L. Chang, Q-Y. Qian, M-T. Zhao, and J. Wang, Int.J. Mass Spectrom. Ion Proc.,139, 95- 102 (1994). The Absolute Isotopic Composition of Europium. 94BIE1 P. De Bievre, S. Valkiers, and H. S. Peiser, J. Res. Natl. Inst. Stand. Technol., 99, 201-202 (1994). New Values for the Silicon Reference Materials, Certified for Isotope Abundance Ratios. 94VAL1 S. Valkiers, F. Schaefer, and P. De Bi?vre, Separation Tech. (E.F. Vansant, Edit) 965-968 (1994). Near-absolute Gas (isotope) Mass Spectrometry: Isotope Abundance (and Atomic Weight) Determinations of Neon, Krypton, Xenon and Argon. The Absolute Isotopic Composition of Cerium. 96TAY1 P.D.P.Taylor, and P. De Bi?vre, Proc. 2nd Nier Symp. on Isot. Mass Spectrom, AECL report (AECL-11342), 90-94 (1996). Unconventional Stable Isotope Mass Spectrometry of Pt, Fe and W via Gas Source Mass Spectrometry. 97CHA1 T.L. Chang, and G.S. Qiao, Chin. Chem. Letters, 8, 91-94 (1997). Determination of the Atomic Weight of Samarium. 97GON1 R. Gonfiantini, P. De Bi?vre, S. Valkiers and P.D.P. Taylor, IEEE Trans. Instrum. and Meas., 46, 566-571 (1997). Measuring the Molar Mass of Silicon for a Better Avogadro Constant: Reduced Uncertainty. 97HUA1 M. Huang, and A. Masuda, Anal. Chem., 69, 1135-1139 (1997). Measurement of the Atomic Weight of Ruthenium by Negative Ionization Mass Spectrometry. 97Q1 H.P. Qi, M. Berglund and P. De Bi?vre, Int.J. Mass Spectrom. Ion Proc. (1998) Calibrated Measurement of the Isotopic Composition and Atomic Weight of the Natural Li Isotopic Reference material IRMM-016. APPENDIX B: SOURCES OF REFERENCE MATERIALS IAEA Reference and intercomparison samples such as VSMOW, SLAP, GISP, LSVEC, NSVEC, NBS18 and NBS19 may be purchased from: International Atomic Energy Agency Section of Isotope Hydrology P. O. Box 100 1400 Vienna, Austria NIST NIST Standard Reference Materials may be purchased through: Standard Reference Material Program National Institute of Standards and Technology Gaithersburg, MD 20899 U.S.A. IRMM Reference Materials may be obtained through: Institute for Reference Measurements and Materials Commission of the European Communities-JRC B-2440 Geel, Belgium CEA CEA distributes stable isotopes through its daughter company: EUROISA-TOP Parc des Algorithmes (Bat. Hom?re), F-91190 St Aubin, FRANCE For nuclear reference materials, see also: CETAMA CEA/DCC Centre d'Etudes Nucl?aires de Fontenay aux Roses BP 6 F 92265 Fontenay aux Roses FRANCE NBL Standards may be obtained through: U.S. Department of Energy New Brunswick Laboratory