Talk:Activity coefficient

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[edit] Deviations from Raoult's Law

Can someone provide information on how activity coefficients demonstrate either positive or negative deviations from Raoult's Law? 171.64.133.56 22:53, 24 February 2006 (UTC)

[edit] Examples; normalisation

This article, which is indirectly referenced from the pH value article, is in desperate need of more explanation. We need an example where the activity coefficient is given as an actual number, not just relative to other activity coefficients.

Am I right in guessing that the normalisation is such that the activity coefficient approaches one as the mixture is diluted?

The article does not currently give a definition of the term.

RandomP 16:16, 19 September 2006 (UTC)

[edit] Article re-written

I hope that the re-write addresses these issues, amongst others.Petergans 10:39, 23 July 2007 (UTC)

[edit] Uncharged species and other corner cases

It would be nice if the article also mentioned how one is to approach:

  • the activity coefficients for electrically uncharged species,
  • activity of the solvent,
  • activity of solids submerged in concentrated electrolytes. —Preceding unsigned comment added by Stan J Klimas (talk • contribs) 20:27, 21 October 2007 (UTC)
Activity coefficients for carbohydrates is an active field of research. Try Google on "activity coefficient carbohydrate". I remember this also being discussed in an ancient text book but can't remember the authors for sure. Were they perhaps Robinson and Stokes?Petergans 11:27, 25 October 2007 (UTC)
Thank you. Indeed, e.g.: "Temperature dependence of water activity in aqueous solutions of sucrose", Food Chemistry, Volume 96, Issue 3, June 2006, Pages 346-370, 3rd International Workshop on Water in Foods.
"-15 to +150 °C, sucrose concentrations up to 98% wt. The isotherms of water activity coefficient exhibit a characteristic minimum at about 96% wt. sucrose which is then followed by a dramatic increase to values well exceeding 1". Stan J. Klimas 21:44, 28 October 2007 (UTC)