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Universal indicator. A universal indicator is a pH indicator made of a solution of several compounds that exhibit various smooth colour changes over a wide range pH values to indicate the acidity or alkalinity of solutions. A universal indicator can be in paper form or present in a form of a solution. [1]
A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. [1] Hence, a pH indicator is a chemical detector for hydronium ions (H 3 O +) or hydrogen ions (H +) in the ...
For more precise measurements, the color can be measured using a colorimeter or spectrophotometer. A Universal indicator is a mixture of several indicators that can provide a continuous color change over a range of pH values, typically from about pH 2 to pH 10. Universal indicator paper is made from absorbent paper that has been impregnated ...
Phenolphthalein (/ fɛˈnɒl (f) θəliːn / [citation needed]feh-NOL (F)-thə-leen) is a chemical compound with the formula C 20 H 14 O 4 and is often written as " HIn ", " HPh ", " phph " or simply " Ph " in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in ...
Methyl orange is a pH indicator frequently used in titration because of its clear and distinct color variance at different pH values. Methyl orange shows red color in acidic medium and yellow color in basic medium. Because it changes color at the p Ka of a mid strength acid, it is usually used in titration of strong acids in weak bases that ...
Bromothymol blue (also known as bromothymol sulfone phthalein and BTB) is a pH indicator. It is mostly used in applications that require measuring substances that would have a relatively neutral pH (near 7). A common use is for measuring the presence of carbonic acid in a liquid. It is typically sold in solid form as the sodium salt of the acid ...
Thymol blue (thymolsulfonephthalein) is a brownish-green or reddish-brown crystalline powder that is used as a pH indicator. It is insoluble in water but soluble in alcohol and dilute alkali solutions. It transitions from red to yellow at pH 1.2–2.8 and from yellow to blue at pH 8.0–9.6.
Litmus is a water-soluble mixture of different dyes extracted from lichens. It is often absorbed onto filter paper to produce one of the oldest forms of pH indicator, used to test materials for acidity. In an acidic medium, blue litmus paper turns red, while in a basic or alkaline medium, red litmus paper turns blue.