Subject: Re: CCL:Avogadro's number

From: "Gershom (Jan M.L.) Martin" <[email-masked]>
Date: Fri, 12 Mar 1999 16:02:42 +0200

Luis Salvatella Ibáñez wrote:
> 
> Dear CCLers,
> 
>  The Avogadro's number was firstly determined by Loschmidt in 1865, 9
> years after the death of
> Avogadro. This calculation was based on the application of the kinetic
> theory of gases. 
Incidentally, in German-speaking countries Avogadro's number is
known as Loschmidt's Number.

JM
---------------------------------------------------------------------
dr. Jan M.L. Martin          Senior Lecturer, Computational Chemistry
     Department of Organic Chemistry/Kimmelman Building, Room 262
        Weizmann Institute of Science/IL-76100 Rechovot/ISRAEL
Email:       [email-masked]       Phone: +972(8)9342533
Web site:  http://theochem.weizmann.ac.il/        FAX: +972(8)9344142
***   finger [email-masked] for PGP public key   ***
-- kol ha`olam kulo gesher tzar meod v'ha`ikar lo l'hitpached klal --

---

From: Chris Harwell <[email-masked]>
Date: Sun, 14 Mar 1999 12:38:49 -0600 (CST)

> > On Thu, 11 Mar 1999, Anatoli Korkin wrote:
> > > Last time I was visiting my dentist, he asked me how Avogadro
> > > could come with his number at that time. 

> On Thu, 11 Mar 1999, Chris Harwell wrote:
> > someone else actually came up with the number after boltzmann & maxwell
> > came up with the necessary stat. mech.

On Fri, 12 Mar 1999, Peter Shenkin wrote:
> Sigh.  What do they teach in freshman chemistry these days?

oh. so sorry -- Dr Shenkin you must be right!  Freshman chemistry was sooo
much better in the old days....

> Based on the observation that gasses combine chemically in the
> ratio of small whole numbers, Avogadro *hypothesized* that equal
> volumes of gasses (at the same T & P) have the same number of
> molecules.  I believe this was around 1811.
> 
> Still, nobody knew what the number was.  In the late 19th century,
> people referred to Loschmidt's number, which was something like the
> number of molecules in a gram of hydrogen gas.
actually peter i think it is more like this:

in 1865 J. Loschmidt worked out a good value for Avagadro's number.
Loschmidt actually got a number bearing his name as well: the number of
moles in 1 cubic centimeter of gas at standard temperature and pressure.
this is also equal to Avagadro's number divided by 22415. or something
like 2.68683 * 10^19.

> It could
> be approximated from the kinetic theory of gasses by comparing
> several measurements;  this gave the right order of magnitude.
i think that is what Loschmidt did.

> This is what Chris is referring to, I think (though I wouldn't
> call it stat mech).
well yes. Maxwell & Boltzmann in the 1860s independently worked out what
became the kinetic theory of gases.  this being "a statistical treatment
of the microscopic constituents of a system in order to predict 
macroscopic properties".  it would seem appropriate to call it
statistical mechanics. what else would one call it?