ethanol - denatured or undenatured?

[Kathryn]

Hi
Could someone please tell me the difference between denatured or undenatured ethanol? Does it make a difference to pracs? I usually purchase denatured but it is not in stock atm at my preferred supplier.
thanks
Kathryn

[Labbie]

Absolute (99-100%) ethanol

Some procedures that are sensitive to the presence of water require absolute ethanol. A common method to produce ethanol with a higher concentration than 95% is to use additives that disrupt the azeotrope composition and allow further distillation. For this reason, absolute ethanol sometimes contains trace amounts of these additives (such as benzene). Absolute ethanol is hygroscopic (it attracts water), so don’t expect it to remain ‘100%’ ethanol for long if it’s left uncapped.

3) Denatured ethanol

Denatured ethanol (either 95% or absolute) contains additives (such as methanol and isopropanol) that render it unsafe to drink, and therefore exempt from certain beverage taxes. This makes it cheaper than pure ethanol.