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: g of unreacted