The reaction between alcohol and acidified potassium dichromate is a redox reaction. This reaction can be used to detect a drunken driver.
Alcohols can be oxidized to aldehydes, ketones and carboxylic acids depending on the structure of the alcohol. Primary alcohols yield adehydes and carboxylic acids while secondary alcohols are oxidized to ketones.
The colour of the acidified potassium dichromate turns from orange to green when exposed to alcohols from the breath of a drunken driver.
