The acid number (AN) is one of the analytical parameters
usually employed to evaluate the quality of biodiesel. It represents
the corrosive potential of biodiesel, which can reduce the
lifetimes of fuel tanks and vehicle engines. This parameter,
commonly expressed as the weight of potassium hydroxide
(in mg) per weight of sample (in g), is related to the fuel’s overall
content of titratable acids, which is derived from the oxidation of
the fuel or from the oil or fat used for its production