composition is . * -= 204 x 1078 from 79 activation anaivsis measurements cver a 10 m year gerilod. : - o. ; 1A73 The observed standard deviation is 20.46 « oo, _ deviation of the mean is 29.905 «x 10 -3 10 and the standard ~. Interlaboratory standards containing 29, and ‘I in a basic XI solution at three difiterent isotopic ratios were received at the Battelle Pacific Northwest Laboratory (PNL) from Dr. O.K. Manuel of the University of Missouri (12). These standards were analyzed at 2NL 3y the activation analysis method described in this paper and in Dr. Manuel's laboratory by an activation analvsis method that uses mass spectrometric Xe isotope ratio determinations (13). Surements + Gocd at . doth . , Laboratories were agreement between the based on . : Laboratories was the NBS 129 I . standard . observed over a Mea- , (SRM=-4949), 129 4 . “““I concentration range of 10 , as shown in Table fl. TABLE LI Interlaboractory Comparison of Activation Analysis Resuits 127, 129, (me) (atoms ) Sample Lab* tMR=10-(129,53)No. 1 UMR 10.0 (gravimetric) PNL 1143 UMR=10-(129,53)No. 2 UMR 1.0 (gravimetric) UMR-10-(129,53)No. 3 UMR 1.0 (gravimetric) *UMR: PNL: PNL 1.0+0.3 PNL 0.8+0.3 University of Missouri, Rolla Pacific Northwest Laboratory ? 129, 127, (atom ratio) 5.2920.29x107° 3.040.7x1019 5,620.4x107> 2.720.lx10l2 §,720.6x1077 5.41077 §.4x1079 , 2.220.7x1019 5,741.8x107? | oe: so a

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