The Avogadro Project!

In the previous post, I talked about how 1Kg of mass is standardized by the  International Bureau of Weights and Measures (BIPM), France.
But it had its own drawbacks. [Where did 1-kilogram come from?]

To overcome all those drawbacks a new approach was taken forward by the Centre for Precision Optics, Australia
the International Avogadro Coordination‘s Avogadro project would define and delineate the kilogram as a 93.6 mm diameter sphere of silicon atoms. Silicon was chosen because a commercial infrastructure with mature processes for creating defect-free, ultrapure monocrystalline silicon already exists to service the semiconductor industry. To make a practical realization of the kilogram, a silicon boule (a rod-like, single-crystal ingot) would be produced. Its isotopic composition would be measured with a mass spectrometer to determine its average relative atomic mass. The boule would be cut, ground, and polished into spheres. The size of a select sphere would be measured using optical interferometry to an uncertainty of about 0.3 nm on the radius—roughly a single atomic layer. The precise lattice spacing between the atoms in its crystal structure (≈192 pm) would be measured using a scanning X-ray interferometer. This permits its atomic spacing to be determined with an uncertainty of only three parts per billion. With the size of the sphere, its average atomic mass, and its atomic spacing are known, the required sphere diameter can be calculated with sufficient precision and low uncertainty to enable it to be finish-polished to a target mass of one kilogram.

As described in Carbon‑12 above, this method would define the magnitude of the kilogram in terms of a certain number of 12C atoms by fixing the Avogadro constant; the silicon sphere would be the practical realization. This approach could accurately delineate the magnitude of the kilogram because the masses of the three silicon nuclides relative to 12C are known with great precision.

To watch video on the above information click on the link below.
It is one of the best Youtube channels you will ever come across. Do like and subscribe.

World’s Roundest Object!



PHOTO AND INFORMATION CREDIT: By The Commonwealth Scientific and Industrial Research Organisation of Australia, CC BY-SA 3.0,


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