The 'new' kilogram is approaching

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The 'new' kilogram is approaching

Post by Lurker on Wed Feb 09, 2011 10:56 am

The 'new' kilogram is approaching

A milestone in the international Avogadro project coordinated by the Physikalisch-Technische Bundesanstalt (PTB) has been reached: With the aid of a single crystal of highly enriched 28Si, the Avogadro constant has now been measured as exactly as never before with a relative overall uncertainty of 3x10^(-8 ). Within the scope of the redefinition of the kilogram, the value NA = 6.02214078(18) • 1023 mol permits the currently most exact realization of this unit. The results have been published in the most recent edition of the journal "Physical Review Letters". [..]

[..]
The result is a milestone on the way towards a successful realization of the new kilogram definition on the basis of fundamental constants whose values have been fixed. At present, the agreement of this value with other realizations of the kilogram is not good enough to change the existing definition of the mass unit. The present state of the Avogadro project is, however, so promising that - on the basis of new measurements with improved sphere interferometers - the measurement uncertainty of 2 • 10^(-8 ) demanded by the Consultative Committee for the Mass (CCM) will in the near future be achieved on contamination-free spheres and will probably even be undercut.

Full article here:
->click<-

Link to the Physikalisch-Technische Bundesanstalt:
PTB


What's the Avogadro Constant?
The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant. We describe a new approach for its determination by counting the atoms in 1 kg single-crystal spheres, which are highly enriched with the 28Si isotope. It enabled isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, NA=6.022 140 78(18)×1023  mol-1, is the most accurate input datum for a new definition of the kilogram.
©️ 2011 The American Physical Society


Link to the Bureau International des Poids et Measures in Sevres, Paris where the standard kilogramm is kept in a safe:
http://www.bipm.org/en/home/

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Interesting times we live in Cool

Summary: The definition of the standard kilogramm which is in effect since 1888/1889 will get a redefinition in the near future Smile


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Lurker

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Re: The 'new' kilogram is approaching

Post by Joe Bese on Wed Feb 09, 2011 11:18 am

Lurker wrote:The 'new' kilogram is approaching
Interesting times we live in

+1
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Re: The 'new' kilogram is approaching

Post by Chiral on Thu Feb 10, 2011 5:27 am

http://www.usgs.gov/newsroom/article.asp?ID=2661


They're also revising the atomic weights of 10 elements.
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Re: The 'new' kilogram is approaching

Post by Exogenisis on Thu Feb 10, 2011 6:32 am

What is/was Wrong with Pound's & Ounces?

It worked for over 1000 Years

How can we Trust a system that Needs to Keep Changing ?


The Sooner we Dump The Metric system and go back to Tried and Trusted The better
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