Bromthymol Blue Recipe

Bromthymol blue is an indicator used to show the presence of an acidic solution. Low levels of acid will result in the bromthymol blue solution remaining blue, while higher levels of acid will result in the bromthymol blue solution taking on a yellow tint. Bromthymol blue is also used to measure photosynthetic activity (solution turns blue as CO₂ is used) or respiratory activity (solution turns yellow as CO₂ is added to the solution).

Aqueous version

1. Add 0.1g Bromthymol blue into 16ml of 0.01N NaOH
2. Mix in a mortar or small tube
3. Dilute to 250ml with distilled water
4. Use 5 drops in 10ml of test solution

Alcohol version

1. Add 0.5g of Bromthymol blue into 500ml of 95% ethanol and dissolve
2. Add 500ml of distilled water
3. Filter and store at room temperature