The Absolute Isotopic Abundance and Atomic Weight of a Reference Sample of Silver

Abstract

The atomic weight of a reference sample of silver has been determined by mass spectrometry. with an uncertainty of one part in 100. using a single filament silica gel procedure. Accurately known quantities of chemically pure 107Ag and H19Ag were mixed to produce standards of known isotopic composition for calibration of the mass spectrometer. The absolute isotopic ratio of the reference sample of silver is 107 AglI09Ag = 1.07638 ± 0.00022 yielding an atomic weight of 107.86815 ± 0.00011. The indicated uncertainties represent an overall limit of error at the 95 percent confidence level which is the sum of the uncertainty components for the ratio determined and the components covering effects of known sources of possible systematic error.

Calibration of isotope amount ratios by analysis of isotope mixtures

“…Hence, measurements of three distinct materials are necessary. Traditionally this has been achieved in its simplest form -by separately measuring both isotopically enriched materials and one blend of the two [10,17].…”

Atomic weights of the elements 1981

“…At this meeting, the Commission considered a new determination of the absolute abundance ratio of silver by Powell, Murphy and Gramlich (Ref. 8) who reported an atomic weight for a reference sample of silver of 107.86815 ± 0.00011 calculated from a '°7Ag/'°9Ag ratio of 1.07638 ± 0.00022. These authors also reported results for a number of silver metal and mineral samples the average value of which was identical with the above number but with a slightly higher uncertainty.…”

Recalculation of the Faraday Constant Due to a New Value for the Atomic Weight of Silver

“…total uncertainty (at a level of one standard deviation) in the atomic weight of silver reported in ref. [3) would shrink from 0.5 ppm to 0.3 ppm [9). It is this latter uncertainty which we have used in the results reported above.…”

“…ThUll the new measurement of the atomic weight of silver reported in ref. [3] has reduced the role of atomic weight in the uncertainty calculation of the Faraday experiment from dominance to insignificance. …”

“…F where E Ag is the electrochemical equivalent of pure silver and Ar(Ag) is the atomic weight of the silver used in determining E Ag' In 1975, coulometric measurements of E Ag undert~ken at the National Bureau of Standards [I]l achieved sufficiently high precision to warrant a careful re-evaluation of the purity of the silver used [2] as well as a more accurate redetennination of its atomic weight [3]. This last work, which is the previous paper published in this issue of the Journal of Research, completes our efforts to measure F via the silver coulometer.…”