A universal indicator is a pH indicator that displays several color changes across a wide range of pH values. Like litmus paper and individual pH indicators, universal indicator indicates the acidity of alkalinity of solutions. But, individual dyes typically change color over a narrow pH range, while universal indicator works for acids, neutral solutions, and bases and turns a whole rainbow of colors.
Universal Indicator Chart
You’re welcome to download and print the universal indicator chart for use in classrooms, labs, or at home. This table lists typical colors and pH values for universal indicator solution:
These colors come from the interactions between the dyes in universal indicator, which are usually thymol blue, methyl orange, methyl red, bromothymol blue, and phenolphthalein:
|Indicator||Low pH Color||Transition Range||High pH Color|
|Thymol blue (first transition)||Red||1.2 – 2.8||Yellow|
|Methyl orange||Red||3.2 – 4.4||Yellow|
|Methyl red||Red||4.8 – 6.0||Yellow|
|Bromothymol blue||Yellow||6.0 – 7.6||Blue|
|Thymol blue (second transition)||Yellow||8.0 – 9.6||Blue|
|Phenolphthalein||Colorless||8.3 – 10.0||Pink or Red|
Color charts are a good starting point for experiments, but it’s best if you calibrate your indicator solution. Record actual colors from testing chemicals of known pH values.
How to Make Universal Indicator
Universal indicator solution is readily available online. However, it’s easy to make it yourself. There are several universal indicator recipes. Most are variations of Yamada’s patent from 1933.
Classic Universal Indicator Solution Recipe
- Methyl red
- Bromothymol blue
- 95% ethanol
- Distilled water
- Dissolve 0.18 g methyl red and 0.36 g phenolphthalein in 550 ml of 95% ethanol.
- In a separate container, dissolve 0.43 g bromothymol blue in 300 ml of distilled water.
- Mix the two solutions together and dilute using distilled water to a final volume of 1 L.
- Add 0.1 M sodium hydroxide (NaOH) dropwise until the indicator solution turns green.
Store the indicator solution in a sealed container. It has a shelf life of around 3 years.
Easy Universal Indicator Recipe
This recipes uses more indicator dyes, but it requires fewer steps.
- 0.1 g phenolphthalein
- 0.2 g methyl red
- 0.3 g methyl orange
- 0.4 g bromothymol blue
- 0.5 g thymol blue
- Dissolve the dyes in a mixture of 250 ml ethanol and 250 ml water.
The universal indicator solution has a shelf life around 3 years in a sealed container.
Cabbage Juice Universal Indicator Recipe
- Chop or blend a red or purple cabbage. If you use a blender, add the minimum amount of water you need.
- Microwave the blended cabbage until it’s soft. Alternatively, cook it on a stove.
- Let the cabbage cool.
- Use a strainer and filter the liquid.
Cabbage juice indicator lasts a couple of weeks refrigerator or indefinitely if it’s frozen until use. While there are color charts for this indicator, it’s better to make your own because each cabbage contains slightly different amounts of various anthocyanins.
Make Universal Indicator pH Paper
Once you have universal indicator, making pH paper is simple. Soak filter paper with indicator solution. Apply the indicator solution using a dropper for easiest clean-up. Let the paper dry and then cut it into test strips.
Don’t dip test strips into liquid! Use a dropper and apply a drop of test liquid to one end of the strip. Then, compare the color against a chart.
- Foster, L. S.; Gruntfest, I. J. (1937). “Demonstration experiments using universal indicators”. Journal of Chemical Education. 14 (6): 274. doi:10.1021/ed014p274
- Rasouli, Zahra; Abdollahi, Hamid; Maeder, Marcel (2020). “Generalized indicator-based determination of solution pH”. Analytica Chimica Acta. 1109: 90-97. doi:10.1016/j.aca.2020.03.004
- Schwarzenbach, Gerold (1957). Complexometric Titrations. Translated by Irving, Harry (1st English ed.). London: Methuen & Co.
- Walker, Denise (2007). Acids and Alkalis (1st ed.). London: Evans. ISBN 0-237-53002-3.
- Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). New York: Houghton Mifflin Company.