Practical investigations
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I have just begun research into a coursework investigation on wine acidity. What defines a volatile acid (i.e. which commonly present acids in wine are volatile), and what's the best way to identify the end point (when only fixed acidity remains in wine) during distillation?
Corrie writes ...
There is no sharp cut-off point that defines a volatile acid, although simple carboxylic acids with 6 C-atoms or less are generally regarded as 'volatile'.
Volatile acids, in the context of wines, are those low molecular mass acids that have low enough boiling points to vaporise sufficiently to be detected by smell (and therefore taste), and the 'volatile acidity (VA) index' is an important quantity here. Ethanoic acid (B.Pt. 118 C) is the main acid contributing to this index in wine.
Testing drops of the distillate on universal indicator paper as the distillation proceeds (especially as the temperature rises close to that of water) will tell you when no more volatile acids are distilling over.
Have you read the tutorial 'Investigating Wines (revisited)' on the React site and followed up the references and previous FAQs therein - some of the information there may be useful to you?
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
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updated: 05 February 2007
