CINF 18 |
| Currently, NA is the number of entities in 12 g of carbon 12. We would like a new simpler definition, integrating it with the redefinitions of the other base units. To ensure that current proposals to improve the International System of Units (the SI) are widely discussed and understood before any changes are made, such discussions should extend to the US. Under ACS discussion are the mole and its relation to the Avogadro constant. The gram atomic weight of a (pure) substance, later to be known as the mole, grew from the need to calculate the masses of reacting substances without any exact knowledge of the value of the Avogadro constant. This led to the concept of the quantity amount of substance, and its unit the mole, in the 1960s. It also led to the present definition of the mole. We now know the value of NA very precisely leading to recent suggestions that a simpler definition might be adopted, specifying the number of elementary entities that make up a mole, thus fixing the value of NA exactly. Redefining all the SI base units using the values of the fundamental constants of physics as references, will be discussed. |
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Past, Present and Future of the Kilogram
3:30 PM-5:10 PM, Sunday, April 6, 2008 Marriott Convention Center -- Blaine Kern C, Oral
Division of Chemical Information |