Absolute isotopic abundance of terrestrial silver

Abstract

I sotopi c ab unda nce ratios a re reported for a commercial silver ni t rate, 13 sa mples of native silver, a nd 11 silver min erals of various co mpositions an d fr om widely dis tributed d eposits . Coll ateral m easureme nts of known mi xt ures of n early pure sil vel' isotopes permit th e d etermination of a bsolu te ab undance rat ios. Native sil ver from Cobalt , Ontario, prev iously r eported as ex hibi t in g s tatist ically s ig nifi can t vari ation, is re-examin ed. Additional meas ure ments a re repo rted for samples from t h e sa me nugget a nd from t he same region. Except fo r t he original observation, no sign ifi cant variation from normal a bundance is obser ved for a ny of t h e sa mples. Th e AgI 07(AglOO ratio obtain ed from p oolin g t h e data is 1.07597 wi t h a 95 p erce nt co nfid ence limi t of ± 0.00055 for t he effect of ra ndom erro rs a nd a total uncer tain ty of ± 0.001 35 when an allowance for the possible effects of known sour ces of sys tematic error is in cluded.

Absolute isotopic abundance ratios and atomic weight of magnesium

“…To insure against this memory effect, the shield and first two plates of the source were replaced with a clean set whenever a sample change ~m~. 1 …”

“…The prebaking of the ionizing filaments, com· bined with the efficient secondary electron suppression grids in the collector, eliminated this problem. Aside from an alcohol wash, the sample filaments were not pretreated in any manner; prebaked sample filaments 1 A de tailed d esc ription of th e a nal ytical procedure is give n U1 re fe re nce [15J.…”

“…In the present study the mass spectrometers used were calibrated for bias by the use of samples of 1 Figures in brackets indicate the lit erature references a1 the end of this paper.…”

Absolute isotopic abundance ratio and the atomic weight of bromine

“…It may be attribu ted to a difference in purity between the mineral sam ples and the reference. In general it is more difficult to obtain standard intensity levels durin g mass spectrometric analyses of natural samples as compared to reference samples [1] and it was observed that the Br 79 /Br 81 ratios obtain ed in the more difficult (higher filam ent temperature) analyses were consistently lower than LllOse obtained in the less difficult (lower filament temperature) a nalyses. • ( I1r"/Br81) sample/(Br"/BrSl ) reference.…”

“…atomic weights of many of the elemen ts. Rece~1t mass spectrometric determinations of the atomic weio'hts of silver [1) I and chlorine [2) .0210 ± 0.0020, and 1.0217 ± 0.0002, respectIvely. However, none of these studies included a direct meaSUl"ement of instrumental bias and, therefore, the resulting ra,tios were not absolute.…”