How to Read an Indicator Color Chart

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Indicator color charts come in different varieties and are used to show the pH of a substance. Chemical compounds that change color in response to acid or base materials are usually embedded in a piece of paper or other substrate. The substance being tested is then applied, turning the compound a new color. The simplest ones, known as litmus tests, will reveal a pH above or below 7 (neutral). More sophisticated color indicators can tell the range of the pH for the substance being tested.

    Apply the substance you are testing to your litmus paper. Red litmus paper is used to detect a base and will turn blue. Blue litmus paper will detect acid and turn red.

    Apply the substance you are testing to a hydrion paper tester. Hydrion papers can detect a range of pHs. The smaller ranges might go from 3 to 7 pH. A full range can cover almost the entire pH spectrum up to 14. The advantage of the smaller range papers is that they are more precise and can show pH to the decimal point (for example, 3.5), where the full range papers cover only whole numbers (like 9 or 4). When the color of the paper changes, check the color against the key on the hydrion paper package to see the pH.

    Apply the substance you are testing to a universal indicator. Universal indicators are a blend of compounds that respond to the entire range of pH. They can be found in paper form but also in a liquid solution. Pour the substance into the solution or apply it to the paper and note the color change. Generally, the color key follows the same order, with reds being the most acidic, greens in the neutral range and purple for base substances.

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About the Author

Bill Brown has been a freelance writer for more than 14 years. Focusing on trade journals covering construction and home topics, his work appears in online and print publications. Brown holds a Master of Arts in liberal arts from St. John's University and is currently based in Houston.

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  • Beaker With Blue Liquid image by explicitly from Fotolia.com

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