Accurate measurements of the Avogadro and Planck constants by counting silicon atoms

Bettin, H.; Fujii, K.; Man, John; Mana, Giovanni; Massa, Enrico; Picard, A.

doi:10.1002/andp.201300038

Cited by 24 publications

(32 citation statements)

References 35 publications

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“…The latter technique has an additional component of relative standard uncertainty at present equal to 0.45 × 10 −9 [3], the same uncertainty shown in Table 3, but this is considered by the research teams to be negligible compared to the total uncertainty budgets of either of the two ways to realize the new Unauthenticated Download Date | 5/10/18 11:11 PM definition of the kilogram (see [38,39], however, the uncertainties given therein refer to older values, now superseded [3]). …”

Section: Choices Within Constraintsmentioning

confidence: 99%

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A critical review of the proposed definitions of fundamental chemical quantities and their impact on chemical communities (IUPAC Technical Report)

Marquardt

Meija

Mester

et al. 2017

Pure and Applied Chemistry

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Abstract:In the proposed new SI, the kilogram will be redefined in terms of the Planck constant and the mole will be redefined in terms of the Avogadro constant. These redefinitions will have some consequences for measurements in chemistry. The goal of the Mole Project (IUPAC Project Number 2013-048-1-100) was to compile published work related to the definition of the quantity 'amount of substance', its unit the 'mole', and the consequence of these definitions on the unit of the quantity mass, the kilogram. The published work has been reviewed critically with the aim of assembling all possible aspects in order to enable IUPAC to judge the adequateness of the existing definitions or new proposals. Compilation and critical review relies on the broadest spectrum of interested IUPAC members.

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Section: Choices Within Constraintsmentioning

confidence: 99%

“…More and more laboratories are currently being equipped with the experimental tools of either of the two available experimental protocols to realize the kilogram [38,39,116]. Concern was raised that only a few countries in the world will be capable of affording the realization of the kg in the proposed new SI [49].…”

Section: Metrological Aspectsmentioning

confidence: 99%

A critical review of the proposed definitions of fundamental chemical quantities and their impact on chemical communities (IUPAC Technical Report)

Marquardt

Meija

Mester

et al. 2017

Pure and Applied Chemistry

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show abstract

“…The effect of fixing the numerical value of the Planck constant is a definition of the unit kg m 2 s −1 (the unit of the physical quantity called action). Together with the definitions of the second and the metre, this leads to a definition of the kilogram; macroscopic masses can be measured in terms of h, Δν( 133 Cs) hfs and c. One way of establishing a mass scale is by counting the number of atoms in a silicon single-crystal sphere using the X-ray crystal density (XRCD) approach -probing the regular arrangement of atoms in a perfect latticeand multiplying it by the known mass of a silicon atom (the 28 Si isotope) 1 . Another route to the kilogram is based on balancing electric and gravitational forces in a so-called watt balance 2 : in this scheme, the weight of a test mass is compared with the force generated by a coil, the electric power of which is measured very accurately by making use of the Josephson and quantum-Hall effects.…”

Section: Focus | Commentarymentioning

confidence: 99%

The new system of units

Fischer

Ullrich

2016

Nature Phys

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“…= M( C) 12 g/mol (exactly) 12 The SI value of the molar mass constant, M u (= M( 12 C)/12), is 1 g/mol (exactly). This was a useful way to define the mole (in 1971) because M(X) is found simply from tabulated values of the relative atomic masses.…”

Section: Avogadro Constantmentioning

confidence: 99%

What Is a Kilogram in the Revised International System of Units (SI)?

Davis

2015

J. Chem. Educ.

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The definition of the kilogram, the unit of mass in the International System of Units (SI), has not changed in more than 125 years. The kilogram is still defined by the mass of a Pt−Ir cylinder conserved at the International Bureau of Weights and Measures. Science and technology have progressed to the point where it is likely the kilogram will be redefined in 2018 in terms of a constant of physicsthe Planck constant, which is closely linked to the Avogadro and atomic mass constants. In this article, we illustrate by means of a simple experiment on how analytical chemistry is contributing to this project, how the new definition of the kilogram will be put into practice and what it may mean for chemists. Surprisingly, perhaps, this simple experiment allows us to determine the mass of an aluminum-27 atom, the mass of a carbon-12 atom (and the atomic mass constant), the Avogadro constant, and the Planck constantall with uncertainty less than 1%in close analogy to the way the most accurate experiment of this type achieves an uncertainty of parts in 10 8 . Finally, we point out that a very different area of modern technology, namely voltage and resistance measurements using quantum electrical devices, provides a second high-accuracy way to implement the new definition.The present definition of the kilogram is based on the mass of a cylinder made of a platinum−iridium alloy and placed into service in 1889. Known as the international prototype of the kilogram (IPK), it is conserved at the International Bureau of Weights and Measures (BIPM), in a suburb of Paris ( Figure 1). Since 1889, the kilogram has been defined as "the mass of the international prototype of the kilogram". As a consequence, all mass measurements made in units of the International System of Units, or SI, are traceable to the mass of the IPK. 1 This definition of the kilogram was fit for purpose in the late 19th century, but we can do better today.As the needs of science and technology evolved, additional base units were added to the SI. In particular, the ampere (1954) filled a need to express electrical measurements easily in SI units, and the mole (1971) did the same for analytical and physical chemistry.The SI meter and second have both been redefined in terms of physical constants for many years, 1 and there is no intention to change these definitions in the revised SI. We will see in the following how atomic masses on the one hand and quantum electrical devices on the other also provide a way to redefine the kilogram in terms of physical constants, which are inherently stable and universally accessible. In addition, the two seemingly different approacheschemical and electricalare actually complementary.A simple experiment is described, which serves to make these ideas less abstract. The experiment is interesting in its own right because it shows how a single mass measurement made on the type of analytical balance found in most chemistry laboratories can, when combined with measured or tabulated values of quantities that are independent of mas...

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Accurate measurements of the Avogadro and Planck constants by counting silicon atoms

Cited by 24 publications

References 35 publications

A critical review of the proposed definitions of fundamental chemical quantities and their impact on chemical communities (IUPAC Technical Report)

A critical review of the proposed definitions of fundamental chemical quantities and their impact on chemical communities (IUPAC Technical Report)

The new system of units

What Is a Kilogram in the Revised International System of Units (SI)?

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