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There are two types of universal pH indicator :
- Solution : It is composed of the elements indicated above and is more effective in the analysis of colorless solutions. While a universal indicator solution can be used to test any sample, it works best in a clear solution because it is easier to see and interpret the color change.
- Litmus paper or pH indicator : it is a strip of paper impregnated with a universal indicator solution that changes color when in contact with the sample. This method is more practical for identifying the pH of dark solutions.
What the colors of the universal indicator mean
The universal indicator changes color according to the acidity and alkalinity levels of a solution and this allows its pH values to be identified. The range of colors of the universal indicator has different meanings:
- Red : If the pH value is between 0 and 3. This indicates that it is a strong acid.
- Yellow or orange : indicates a pH between 3 and 6, therefore, it identifies a weak acid.
- Green : pH 7 indicates a neutral solution.
- Blue : a pH between 8 and 11, indicates a weak alkalinity.
- Violet or indica : a pH with values between 11 and 14, identifies a strong alkalinity.
Since the formulas vary slightly between different commercial brands on the market, the universal pH indicator usually comes with a table that explains the colors that can be obtained and the pH ranges.
Bibliography
- Moreno Rodríguez, JA; Moreno Rodríguez, LA Fundamentals of Chemistry: Principles of Basic Chemistry . (2012). Spain. Spanish Academic Editorial.
- Gray, H.; Haight, G. Basic Principles of Chemistry . (2009). Spain. Editorial Reverté.
- Tomaylla Cruz, C.; Aragón, J. Basic Chemistry: Theory and Practice . (2019). EAE.
