Preparation of 0.5 McFarland standard
McFarland standard was prepared by adding 0.5 mL of 0.048 mol/L BaCl2 (1.17% w/v BaCl2.2H2O) in to 99.5 mL of 0.18 mol/L H2SO4 (1% w/v) with constant stirring. The equal volume of standard solution was distributed into same sized screw capped test tubes. These test tubes were tightly sealed and stored at room temperature to prevent from evaporation and light. Before use, turbidity standard was vigorously agitated by using vortex mixe