Denatured alcohol is ethanol that contains impurities that make it undrinkable. The impurities are methanol, methyl isobutyl ketone, aviation gasoline etc. It is toxic and 200 ml of it is a fatal dose to an adult. Solution of about 10% ethanol in gasoline (gasohol) is a good motor fuel. Ethanol is commonly called alcohol and is active ingredient of all alcoholic drinks. Consumption of small quantity of dilute ethanol causes drunkenness. In addition, as it is a good solvent it is also used in medicines such as tincture iodine, cough syrups and many tonics

• Do you know how the police detect whether suspected drivers have consumed alcohol or not?

The police officer asks the suspect to blow air into a plastic bag through a mouth piece of the detecting instrument which contains crystals of potassium-di-chromate(K₂Cr₂O₇). As K₂Cr₂O₇ is a good oxidizing agent, it oxidizes any ethanol in the driver’s breath to ethanol and ethanoic acid.

Orange Cr₂O₇ ^2- changes to bluish green Cr3+ during the process of the oxidation of alcohol. The length of the tube that turned into green is the measure of the quantity of alcohol that had been drunk. Now a days police are using even an electronic instrument containing small fuel cell that measures the electrical signal produced when ethanol in the breath is oxidized. The police even use the IR Spectra to detect the bonds C – OH and C – H of CH₃ – CH₂OH.

Chemical properties

As ethanol is similar to water molecule (H₂O) with C₂H₅ group in place of hydrogen, it reacts with metallic sodium to liberate hydrogen and form sodium ethoxide.

Action of conc. H₂SO₄:

Ethanol reacts with conc. H₂SO₄ at about 170oC (443 K) to give ethene. It is a dehydration reaction. H₂SO₄ is a dehydrating agent and removes H₂O.

Ethanoic acid (Acetic acid or CH₃COOH)

Ethanoic acid is a colourless liquid with characteristic unpleasant odour. It is soluble in water and more acidic than H2O or ethanol, but less acidic than mineral acids.