# Talk:Loschmidt constant

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As far as I remember, the Loschmidt constant or number is nothing else but the Avogadro constant. It looks quite strange to call the number of atoms in a gas per cubic meter a constant, since it's only constant at a given pressure and temperature for an ideal gas. --88.68.121.16 18:53, 7 September 2007 (UTC)

## Relationship to Avogadro's Number

The formula given in the article for the relationship between Avogadro's Number and Loschmidts number is:

N(a) = n(0) p/kT


This cannot be right, the first formula has:

n(0) = p/kT


resulting in:

N(a) = n(0)^2


Which is obviously wrong. I am going to make an edit now to correct this. Spinningspark 21:41, 2 October 2007 (UTC)

## Confused

By [1] p. 139, it states that Loschmidt's number is Avogadro's number divided by 22,400. I am confused.--Filll (talk) 21:20, 12 March 2008 (UTC)

From the Avogadro's constant article;
$N_A = 6.02214179 \times 10^{23} \quad molecules/mole\,\!$
According to your book;
$n_0 = \frac {N_A}{22400}=\frac {6.02214179 \times 10^{23}}{22400}=2.6884562\times 10^{19} \quad molecules/ml$
Converting that to per cubic metre;
$n_0 = 2.6884562\times 10^{25} \quad molecules/m^3\,\!$
Which is a fair approximation to the CODATA value quoted in the article of;
$n_0 = 2.6867774\times 10^{25} \quad molecules/m^3\,\!$
Hope that helps you. But note also that this numerical relationship only holds at standard temperature and pressure. Avogadro's constant is absolutely a constant regardless of temperature and pressure. The number density, on the other hand, varies with temperature and pressure and is only equal to Loschmidt's constant at NTP. SpinningSpark 21:38, 13 March 2008 (UTC)

## Derivation of loschmidt constant

I need a little help with some algebra. I am unable to derive the equation for the diameter of an air molecule as per Loschmidt, starting from the Maxwell equation for mean free path as Loschmidt was supposed to have accomplished. I know the equation to start with and I know where it is supposed to end up, but i just cannot make the mathematics air tight. Please help with more detail. Thanks. —Preceding unsigned comment added by 76.191.201.207 (talk) 08:42, 9 February 2010 (UTC)

There's a step missing from the version in the article. Talk:Loschmidt constant/Derivation is a more talked-through derivation. Physchim62 (talk) 13:12, 9 February 2010 (UTC)