How to Make a Bromothymol Blue Solution

Bromothymol blue indicator will turn yellow in an acidic solution.
••• chemical image by Randy McKown from

Bromothymol blue solution is used as an indicator to determine the rough pH of a substance. It is prepared from a powder, household items and common laboratory chemicals that can be obtained through a scientific supply house individually or as a kit. The mixed bromothymol blue solution will turn yellow in an acidic solution and blue in basic solutions.

    Add 0.1 g of bromothymol blue powder to 10 mL of 4 percent sodium hydroxide solution in a large beaker.

    Combine 20 mL of alcohol to the sodium hydroxide/bromothymol blue solution.

    Dilute the mixture with 1 L of distilled water in a large container. The solution should be dark blue in color.

    If the solution appears green, use a pipette to slowly add sodium hydroxide drop by drop to the solution until it changes to blue.

    Things You'll Need

    • 0.1 g bromothymol blue powder
    • 10 mL 4 percent sodium hydroxide solution
    • 20 mL rubbing alcohol
    • 1 L distilled water
    • Beakers
    • Pipette
    • Stirring rod
    • Safety goggles
    • Rubber gloves


    • Sodium hydroxide is a corrosive chemical. Be sure to wear all safety gear, including gloves and goggles. Bromothymol blue should be prepared with scientific grade equipment in a laboratory environment.

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