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An Exact Value for Avogadro's Number


As Na is a count of the number of (atoms/molecules) in a mole of a substance, the shape of the mole seems (to me, at least) to be irrelevant. You can have a mole that is a "flat pancake", or a mole that is a cube, or a mole that is a sphere - doesn't matter - as long as you have a mole. So the "perfect cube" requirement ("Third, the value chosen..." above) seems (again, to me) "bogus", and should be discarded??
posted by SA Holton
February 28, 2011 @ 11:40 PM

I looked at this a while ago and got a closer figure for the FCC cube method with k = 42,223,445
Na* = 602,214,151,767,324,550,096,221

But of course the atoms at the corners wont be bound properly and a cube of carbon in air ends up having a layer of Nitrogen bonded to the surface so making a real one is pointless, but the simplicity and elegance of idea is the point I suppose.
posted by Adam Anderson
July 14, 2011 @ 9:34 AM

After this article came out, I submitted a letter-to-the-editors (AmSci, May/Jun2007, Vol. 95 Issue 3, p195). I suggested that the decay of a mole of radioactive element should end with a whole atom; thus 2^0=1. Going in reverse, the current value of Avogadro’s Number is approximated by 2^79 = 604 462 909 807 314 587 353 088.

In a 1996 copyrighted pamphlet, “Mole, Bits, and Cubes” (TXu000593728), I submitted that this Binary definition should be the value of Avogadro’s Number. It is invariant, free of dimensionality, and free of all the physical measurements currently being used to “hone in” on a value that seems far too prejudiced considering it is all tangled up with a chunk of metal that needs periodic cleaning that removes few bits of matter in the process and is subject to experimental errors in measurements (80 parts in a billion? and at what accuracy/precision).

With N avo = 2^79, the kilogram is as good as measurements can determine the purity, number, and atomic mass of the units of whatever material (e.g., the silicon-28 sphere that is being proffered) is being measured and the standard on which the standards folks make the reference point. Thus, a binary mole of absolutely pure carbon-12 would currently weight precisely 12.0· grams and always be so until they changed the reference point from C-12. At least Avogadro’s “Number” would finally be a “constant” – one and the same.

What I see is a great effort (by those who will be making a decision) not to alter the massive weights and measurements structure that is in place throughout the world of commerce. In that realm, Avogadro’s Number/constant is not a factor - only the size of the “king’s foot”; in this case “Le Gran K” or an article representing it. Science takes second place in this realm.
posted by Joel Williams
March 13, 2013 @ 12:01 PM


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