The standard form of denatured alcohol which is used in most chemistry labs in the UK is DEB (Denatured Ethanol B) 100, so called because it contains 100 parts per million of Bitrex, the bitterest substance known to man.

The reason this is used instead of other forms of adulteration is that this small quantity (0.01%) is 10 times more than is necessary in order to render the alcohol undrinkable, and yet is so small that the final product is essentially still pure ethanol. There are extremly few chemical procedures that require ethanol of greater purity than this, and in all of those circumstances absolute ethanol must be used.