denatured alcohol

Drinkable alcohol is subject to tax in most countries and for industrial use it is denatured to render it unfit for consumption, by the addition of 5% methyl alcohol (methanol, CH₃OH, also known as wood alcohol), which is poisonous. This is industrial rectified spirit. For domestic use a purple dye and pyridine (which has an unpleasant odour) are also added; this is methylated spirit.