Biodiesel sample (2 g) was dissolved in 25 ml of Toluene: Isopropyl alcohol: distilled water (100:147.5:2.5 v/v) with 0.125 ml of p-napthalobenzein as an indicator. The mixture was titrated with 0.01 M alcoholic until the color of the solution changed from green to blue. This amount of 0.1 M alcoholic solution is referred as “C” The amount of acid value can be calculated by using equation 3: Acid value =