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

Bower, V.E.; Davis, Richard; Murphy, Thomas J.; Paulsen, Paul J.; Gramlich, J. W.; Powell, L. J.

doi:10.6028/jres.087.003

Cited by 15 publications

(3 citation statements)

References 7 publications

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“…The largest source of uncertainty in determining F is the atomic weight of silver. The U.S. National Bureau of Standards made a new measurement of the atomic weight of silver by calibrating a thermal ionization mass spectrometer (TIMS) to obtain a value of A r (Ag) ¼ 107.86815 AE 0.00011 to give a marked improvement in the uncertainty of A r (Ag)- (Bower et al, 1982). This enabled a revised value of F of 96.485309 C mol À1 , with a relative uncertainty of 0.30 ppm to be determined (Cohen & Taylor, 1987).…”

Section: Fundamental Constantsmentioning

confidence: 99%

The role of mass spectrometry in atomic weight determinations

Laeter

2008

Mass Spectrometry Reviews

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The 1914 Nobel Prize for Chemistry was awarded to Theodore Richards, whose work provided an insight into the history of the birth and evolution of matter as embedded in the atomic weights. However, the secret to unlocking the hieroglyphics contained in the atomic weights is revealed by a study of the relative abundances of the isotopes. A consistent set of internationally accepted atomic weights has been a goal of the scientific community for over a century. Atomic weights were originally determined by chemical stoichiometry--the so-called "Harvard Method," but this methodology has now been superseded by the "physical method," in which the isotopic composition and atomic masses of the isotopes comprising an element are used to calculate the atomic weight with far greater accuracy than before. The role of mass spectrometry in atomic weight determinations was initiated by the discovery of isotopes by Thomson, and established by the pioneering work of Aston, Dempster, and Nier using sophisticated mass spectrographs. The advent of the sector field mass spectrometer in 1947, revolutionized the application of mass spectrometry for both solids and gases to other fields of science including atomic weights. Subsequently, technological advances in mass spectrometry have enabled atomic masses to be determined with an accuracy better than one part in 10(7), whilst the absolute isotopic composition of many elements has been determined to produce accurate values of their atomic weights. Conversely, those same technological developments have revealed significant variations in the isotope abundances of many elements caused by a variety of physiochemical mechanisms in natural materials. Although these variations were initially seen as an impediment to the accuracy with which atomic weights could be determined, it was quickly realized that nature had provided a new tool to investigate physiochemical and biogeochemical mechanisms in nature, which could be exploited by precise and accurate isotopic measurements. Atomic weights can no longer be regarded as constants of nature, except for the monoisotopic elements whose atomic weights are determined solely by the relative atomic mass of that nuclide. Stable isotope geochemists developed mass spectrometric protocols by the adoption of internationally accepted reference materials for the light elements, to which measurements from various laboratories could be compared. Subsequently, a number of heavy elements such as iron, molybdenum and cadmium have been shown to exhibit isotope fractionation. The magnitude of such isotope fractionation in nature is less than for the light elements, but technological developments, such as multiple collector-inductively coupled plasma-mass spectrometry, have enabled such fractionation effects to be determined. Measurements of the atomic weights of certain elements affect the determination of important fundamental constants such as the Avogadro Constant, the Faraday Constant and the Universal Gas Constant. Heroic efforts have been made to refine the accu...

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Section: Fundamental Constantsmentioning

confidence: 99%

The role of mass spectrometry in atomic weight determinations

Laeter

2008

Mass Spectrometry Reviews

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“…The electrochemical equivalent of silver, which is closely related to the Faraday constant F = N A e , was used at the turn of the century to define and maintain the International Ampere. The measurements at the NIST (NBS) by Bower and Davis [95] yield a value of the Faraday constant when combined with the measurements of the molar mass of silver by Powell et al [96]. The mole is known as accurately as the kilogram and so measurements of F serve to provide valuable input information on the electrical units.…”

Section: The Planck Constant and The Watt Kilogram And Molementioning

confidence: 99%

The Role of the Fundamental Constants of Physics in Metrology

Petley

1992

Metrologia

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The paper discusses the recent measurements of the fundamental physical constants whose various combinations serve to provide the natural units of measurement in physics and the evaluation of their recommended values by the CODATA Task Group on Fundamental Constants. It emphasizes the strong involvement of the SI units with the present evaluations and shows how the fundamental physical constants play an increasing role in defining and maintaining many of the SI units of today and in sustaining the integrity of our measurement system. The present situation is reviewed and the evolving role of the fundamental physical constants in science and technology is discussed.

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“…Craig et al solved this problem by capturing the silver residue on a filter, which was then dried and weighed. In the early 1980s, Bower and Davis [11] and others [12,13] obtained a value of the Faraday constant of 96 486.19 C mol −1 with an uncertainty of 1.3 parts in 10 6 .…”

Section: Introductionmentioning

confidence: 99%

A system for controlling electrical and chemical parameters in the Faraday constant determination by dissolution of silver

Pogliano¹,

Durbiano²,

Serazio³

2011

Meas. Sci. Technol.

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The development of an electrochemical system for the Faraday constant determination has been undertaken at I.N.RI.M. In this system a new two-electrode cell for processing silver dissolution has been set up. The parts of this cell have been carefully designed to avoid sources of undue influence. New elements for monitoring the Ag+ ion concentration in the two half-cells have been introduced and the operations necessary to keep the electrochemical reactions under strict control have been identified and tested. The solution stability, the residue recovery, the O2 prevention and the solution filtering process without its transfer to other containers are other merits. The electrical charge measurement equipment has been assembled and integrated with the one for monitoring the reaction parameters. A control apparatus displaying when some specific operations in the two half-cells are required has been added. The measurements showed that by employing the setup assembled with some proper precautions an uncertainty of about 1–2 parts in 105 can be reached, mainly limited by the silver purity, and the evolution toward a measurement system at a metrological level (parts in 106 or better) is attainable.

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

Cited by 15 publications

References 7 publications

The role of mass spectrometry in atomic weight determinations

The role of mass spectrometry in atomic weight determinations

The Role of the Fundamental Constants of Physics in Metrology

A system for controlling electrical and chemical parameters in the Faraday constant determination by dissolution of silver

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