Practical investigations
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In the experiment to determine ethanol content of wine by the density method (ref. “What is in wine?” – D. Denby, Chem Review Jan 98) it states that the wine has to be made “slightly alkaline” before distillation. Why is this?
Igloo writes
The density method for determining the concentration of ethanol in wine assumes that the distillate mainly contains a mixture of ethanol and water.
There are small quantities of volatile acidic components present in all wines (e.g. ethanoic acid), and these would accompany the water and ethanol into the distillate unless the wine is neutralised beforehand.
By ensuring that the wine is made “slightly alkaline” - using aqueous alkali – you can be certain that all the acids present will have been converted into non-volatile salts. The alkali converts the volatile, molecular acid into its involatile, ionic salt.
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updated: 19 April 2005
