How to Make Bromocresol Green Indicator

Recipe for Bromocresol Green pH Indicator Solution

This is the chemical structure of bromocresol green.
This is the chemical structure of bromocresol green.
By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on December 03, 2018

Bromocresol green (BCG) is a triphenylmethane dye that is used as a pH indicator for titration, DNA agarose gel electrophoresis, and microbiological growth media. Its chemical formula is C21H14Br4O5S. The aqueous indicator is yellow below pH 3.8 and blue above pH 5.4.

This is the recipe for bromocresol green pH indicator solution.

Key Takeaways: Bromocresol Green Indicator Recipe

  • Bromocresol green is a pH indicator that is yellow below pH 3.8 and blue over pH 5.4. Between pH 3.8 and 5.4 it is green.
  • The indicator is made from bromocresol green powder dissolved in ethanol.
  • Bromocresol green is most often used for electrophoresis, titration, and in microbial growth media.

Bromocresol Green pH Indicator Ingredients

  • 0.1 g of bromocresol green
  • ethyl alcohol

Prepare the Bromocresol Green Solution

0.1% in alcohol

  1. Dissolve 0.1 g of bromocresol green in 75 mL of ethyl alcohol.
  2. Dilute the solution with ethyl alcohol to make 100 ml.

0.04% aqueous

  1. Dissolve 0.04 g of bromocresol green in 50 mL of deionized water.
  2. Dilute the solution with water to make 100 ml.

While bromocresol green is usually dissolved in ethanol or water, the dye is also soluble in benzene and diethyl ether.

Safety Information

Contact with bromocresol green powder or indicator solution may cause irritation. Contact with skin and mucous membranes should be avoided.

Sources

  • Kolthoff, I.M. (1959). Treatise on Analytical Chemistry. Interscience Encyclopedia, Inc. New York.
  • Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press. 
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Your Citation
Helmenstine, Anne Marie, Ph.D. "How to Make Bromocresol Green Indicator." ThoughtCo, Aug. 26, 2020, thoughtco.com/how-to-make-bromcresol-green-indicator-608136. Helmenstine, Anne Marie, Ph.D. (2020, August 26). How to Make Bromocresol Green Indicator. Retrieved from https://www.thoughtco.com/how-to-make-bromcresol-green-indicator-608136 Helmenstine, Anne Marie, Ph.D. "How to Make Bromocresol Green Indicator." ThoughtCo. https://www.thoughtco.com/how-to-make-bromcresol-green-indicator-608136 (accessed May 31, 2023).