Subject: Avogadro's Number

From: "S. Parthiban" <[email-masked]>
Date: Thu, 11 Mar 1999 21:57:05 -0800 (PST)

Amedeo Avogadro (1776-1856) in 1811 proposed the hypothesis that 
equal volumes of gases at the same temperature and pressure 
contained the same number of molecules, the latter being stable, 
multi-atomed particles. In point of fact Avogadro's hypothesis was 
without any impact or influence on the calculation of atomic weights at 
this time. Not until the explanatory power of electrochemical theory 
had temporarily waned in the 1850s under the weight of difficulties in 
organic chemistry, and chemists and physicists found it convenient to 
accept (without explanation) that dimers such as H2 and O2 could exist, 
was a complete reconciliation of gravimetric and volumetric data 
possible. Until then the dimerization of like-charged atoms remained
impossible.
 
       -parthi

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From: Luis Salvatella Ibáñez <[email-masked]>
Date: Fri, 12 Mar 1999 12:10:35 +0100

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. In 1913,
Jean Perrin published his book "Les atomes", where the Avogadro's number
was calculated by
means of 13 different ways, this fact being usually considered as the
final victory of the atomic
theory.

 For a very brief explanation of the Loschmidt's calculation, see:

KOHN, MORITZ, Josef Loschmidt. Journal of Chemical Education 1945, 22,
381-384.

 Best wishes,

                           LUIS SALVATELLA