Thread: Avagadro's number: 6.02 x 10^23

I realize that this number is the amount of atoms in a mole.

But does anyone have any idea how that figured that out way back in the 1800's?

Where would we be without wikipedia:

http://en.wikipedia.org/wiki/Avogadro%27s_constant

and then a link from the same page:

http://web.lemoyne.edu/~giunta/Avogadro.html

Those were *real* chemists...

Consider this from wiki:

The Avogadro constant is named after the early nineteenth century Italian scientist Amedeo Avogadro, who, in 1811, first proposed that the volume of a gas (at a given pressure and temperature) is proportional to the number of atoms or molecules regardless of the nature of the gas.

why would volume always be proportional to the quantity of atoms/molecules? As far as I know, a Gas has no definite volume, it can be squeezed into a very tight space, and it can expand to fill a room. So a given volume of gas should not give one any bearing on how many molecules/atoms are within it.

You left out the part about STP, standard temp and pressure, at which it will always be 22.4L

And that is a very important little part. The better question would be how we managed to weigh that gas.