2.4 Titration method for the amount of soap content
Biodiesel sample (5 g) was dissolved in 100 ml of isopropyl
alcohol, followed by addition of 2 ml of 1% phenol red. The
mixture was titrated with 0.01 M hydrochloric acid until the color
of the solution changed from red to colorless. This amount of
0.01 M hydrochloric acid solution is referred as “A”. Then 1 ml of
0.04 % bromophenol blue was added into the mixture solution
and titrated with 0.01 M hydrochloric acid until the color of the
solution changed from blue to yellow. This amount of 0.01 M
hydrochloric acid solution is referred as “B”.
The amount of unreacted catalyst can be calculated by using
equation 1: