Denatured alcohol (CAS 64-17-5), also known as denatured ethanol or industrial methylated spirit (IMS), is ethanol (ethyl alcohol) to which has been added small known quantities of additional substances so as to ‘denature’ or adulterate it in a controlled manner.
The additive is usually methanol (at 5 to 10%) but could also be isopropanol, methyl ethyl ketone, acetone or methyl isobutyl ketone (typically all at 1%), denatonium for a bitter taste, plus a coloured dye such as methyl violet for visual identification, or a combination of any of these.
The primary purpose of denaturation is to render the ethanol unfit, unpalatable and unsafe for recreational human consumption, or unsuitable for any other unauthorised purpose. Denaturation usually makes the product exempt from duty payable and other taxes, hence making it cheaper to purchase.
Denatured alcohol is not normally used for fine analytical or other laboratory applications, but still finds many other uses commercially and in industry:
As a general-purpose solvent especially for removal of adhesives, waxes and paint
For cleaning and degreasing apparatus and equipment
As a fuel for burners and stoves
As a surface disinfectant or steriliser for use in cleanrooms, laboratories and clinical environments, presented as a liquid, spray, gel or wet-wipe
In cosmetics as a preservative and antibacterial
Denatured alcohol with added methanol is acutely toxic. It is flammable at room temperature, so storage in a secure location is recommended. Due attention should also be given to all other appropriate precautions necessary for handling these chemicals.