Saturday, February 12, 2022

Preparation of 3-Nitrophenol indicator solution

Learn the procedure for making a 3-Nitrophenol indicator solution.

The compound that changes color when exposed to acidic or basic solutions is called an indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

3-Nitrophenol/m-nitrophenol (C6H5NO3) is a nitroaromatic compound. It can be prepared from 3-nitroaniline, via diazotization reaction. It comes in a yellow solid which is soluble in water, alcohol, ether, and acetone. It's commonly used as an intermediate in the manufacturing of dyes, lumber preservatives, pigments, photography chemicals, and pesticides.

How to prepare 3-Nitrophenol indicator for titration:

  • Weigh accurately 0.1 gm of 3-Nitrophenol and pour it into a 100.00 ml volumetric flask containing 50.00 ml of distilled water and mix it.
  • Once it is dissolved, dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 1 g/L.

3-Nitrophenol has a pKa of 8.36 and the pH range is 6.6 to 8.6. It transitions from colorless to yellow/orange through the pH range and is used as a pH indicator.



References:
  1. Wikipedia contributors. (2021, February 11). Nitrophenol. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.
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Preparation of 2, 4-dinitrophenol indicator solution

Learn the procedure for making 2, 4-dinitrophenol indicator solution.

The compound that change color when exposed to acidic or basic solutions are called indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

2,4-Dinitrophenol (C6H4N2O5) is an organic compound. It comes in light yellow crystal powder which is sparingly soluble in water; soluble in ethanol, benzene. Dinitrophenol is used to make dye, as a wood preservative, and as an analytical reagent and indicator.

How to prepare 2,4-Dinitrophenol  indicator for titration:

  • Weigh accurately 0.1 gm of 2, 4-dinitrophenol and pour it into a 100.00 ml volumetric flask containing 50.00 ml of water and mix it.
  • Once it is dissolved, dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 1 g/L.

2, 4-Dinitrophenol has a pKa of 3.96 and the pH range is 2.8 to 4.4. It transitions from colorless to yellow through the pH range and is used as a pH indicator.



References:
  1. Wikipedia contributors. (2022, February 11). 2,4-Dinitrophenol. In Wikipedia, Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.

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Preparation of cresol red indicator solution

Learn the procedure for making cresol red indicator solution.

The compound that change color when exposed to acidic or basic solutions are called indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

Cresol red (C21H18O5S) chemically described as o-cresolsulphonphthalein is a triarylmethane dye used as a pH indicator. It comes in dark green or brown-red powder or crystals which is sparingly soluble in water and soluble in ethanol.

How to prepare cresol red indicator for titration:

  • Weigh accurately 20 mg of cresol red and pour it into a 100.00 ml volumetric flask containing 01.06 ml of 0.05N sodium hydroxide solution and 05.00 ml of 95% ethanol.
  • Once it is dissolved, add 15 ml of ethanol and dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 0.2 g/L.

Cresol red has a pKa of 1.0 and pH ranges of 0.2-1.8 and 7.2 to 8.2. At pH 0.2-1.8, it changes from red to yellow, while at pH 7.2 to 8.2, it transitions from yellow to violet-red. It is frequently used as an indicator in acid-base titration.


References:
  1. Wikipedia contributors. (2021, May 8). Cresol Red. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.

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Friday, February 11, 2022

Preparation of bromophenol blue indicator solution

Learn the procedure for making bromophenol blue indicator solution.

The compound that change color when exposed to acidic or basic solutions are called indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

Bromophenol blue (C19H10Br4O5S) chemically described as 3, 5, 3’, 5’-tetrabromophenolsulphonphthalein, is a dye used as a pH indicator. It is prepared by adding slowly excess bromine to a heated phenolsulfonphthalein solution in glacial acetic acid. Bromophenol blue has a similar structure to phenolphthalein. It comes as a pink-orange to red to purple powder, generally used as a fluorescent stain in yeast cells.

How to prepare bromophenol blue indicator for titration:

  • Weigh accurately 40 mg of bromophenol blue and pour it into a 100.00 ml volumetric flask containing 01.20 ml of 0.05N sodium hydroxide solution and 10.00 ml of 95% ethanol, warm it.
  • Once it is dissolved, dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 0.4 g/L.

Bromophenol blue has a pKa of 4.0 and the pH range is 3.5 to 4.6. It is turn yellow below pH 3.5, while it turns blue above pH 4.6, this reaction is reversible. It is mainly used as an acid-base indicator, also used as a dye.


References:
  1. Wikipedia contributors. (2022, January 25). Bromophenol blue. In Wikipedia, The Free Encyclopedia.Available Here: 
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.

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Preparation of bromocresol purple indicator solution

Learn the procedure for making bromocresol purple indicator solution.

Bromocresol purple (C21H16Br2O5S) chemically described, as 5, 5’-dibromo-o-cresolsulphonphthalein, is a dye of the triphenylmethane family (triarylmethane dyes) and a pH indicator. It comes as a pinkish brown crystalline powder, generally used as a fluorescent stain in yeast cells.

Bromocresol purple has a structure that changes with pH, similar to bromocresol green. The acidity level changes cause the shifting equilibrium between two different structures with different colors shifts. The chemical has a sulfonate structure in a near-neutral or alkaline solution, which gives the solution a purple color. It turns into a sulfone (cyclic sulfonic ester) as the pH drops, causing the solution to turn yellow.

How to prepare bromocresol purple indicator for titration:

  • Weigh accurately 40 mg of bromocresol purple and pour it into a 100.00 ml volumetric flask containing 01.48 ml of 0.05N NaOH solution and 10.00 ml of 95% ethanol, warm it.
  • Once it is dissolved, dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 0.4 g/L.

Bromocresol purple has a pKa of 6.3 and the pH range is 5.2 to 6.8. It is turning yellow (below pH 5.2), in acidic solutions, while in a basic condition (above pH 6.8) it turns bluish-violet. It is mainly used in a medical laboratory, acid-base indicator, as a dye, and two-color indicator.



References:
  1. Wikipedia contributors. (2021, May 1). Bromocresol purple. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.
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Preparation of thymolphthalein indicator solution

Learn the procedure for making thymolphthalein indicator solutions.

Thymolphthalein (C28H30O4) is a phthalein dye that is used as an acid-base (pH) indicator. It comes in a white powder that is synthesized from thymol and phthalic anhydride.

Its pH transition range is 9.3–10.5, and its endpoint is a blue color shift. Its transition range is around pH 9.3–10.5; its endpoint is colorless to blue. Thymolphthalein is commonly used as a weak acid and strong base indicator and is also used as a laxative and for disappearing ink.

How to prepare thymolphthalein indicator for titration:

  • Weigh accurately 0.1 gm of thymolphthalein and pour it into a 100.00 ml volumetric flask containing 50.00 ml of 95% ethanol, mix it.
  • Once it is dissolved, dilute to 100.00 ml with water.
  • The concentration of the prepared solution is about 1 g/L.

Thymolphthalein has a pKa of 9.9 and the pH range is 9.3 to 10.5. It is colorless (below pH 9.3), in acidic solutions, while in a basic condition (above pH 10.5) it turns blue. In acid-base titrations, is frequently used as an indicator.


References:

  1. Wikipedia contributors. (2021, December 6). Thymolphthalein. In Wikipedia, Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.


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Thursday, February 10, 2022

Preparation of phenolphthalein indicator solution

Learn the procedure for making phenolphthalein indicator solutions.

The compound that change color when exposed to acidic or basic solutions are called indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

Phenolphthalein (C20H14O4) is a chemical compound often written in shorthand notation as "HIn" or "phph" that belongs to the phthalein family. Phenolphthalein can be formed by condensation of phthalic anhydride with two equivalents of phenol under acidic conditions.

It comes in a yellowish-white to light orange fine crystalline powder. It is a weak acid that, in solutions, can lose H+ ions.

How to prepare phenolphthalein indicator for titration:

  • Weigh accurately 01.00 gm of phenolphthalein and pour it into a 100.00 ml volumetric flask containing 50.00 ml of 95% ethanol, mix it.
  • Once it is dissolved, dilute to 100.00 ml with ethanol.
  • The concentration of the prepared solution is about 10 g/L.

Phenolphthalein has a pKa of 9.7 and the pH range is 8.2 to 10. It is colorless in acidic solutions, while in a basic condition it turns pink. In acid-base titration, is frequently used as an indicator.

References:
  1. Wikipedia contributors. (2022, January 23). Phenolphthalein. In Wikipedia, The Free Encyclopedia. Available Here
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.

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Preparation of m-cresol purple indicator solution

Learn the procedure for making cresol purple indicator solution.

The compound that change color when exposed to acidic or basic solutions are called indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

Meta-cresol purple (C21H18O5S), commonly known as m-cresol purple or m-cresolsulfonphthalein, is a triarylmethane dye and a pH indicator. It comes in a green or brick-red powder that is acidic and hydrophobic in nature, with slightly soluble in water and ethanol. It is primarily used as an acid-base indicator and in spectrophotometric pH measurements. It's also used to stain epithelial cells and proteins.

How to prepare cresol purple indicator for titration:

  • Weigh accurately 40 mg of m-cresol purple and pour it into a 100.00 ml volumetric flask containing 02.08 ml of 0.05N NaOH solution and 20.00 ml of 95% ethanol.
  • Once it is dissolved, dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 0.4 g/L.

m-cresol purple has a pKa of 8.3 and it has two useful pH ranges are 1.2 - 2.8 (red to yellow) and 7.4 - 9.0 (yellow to violet). It changes color in both pH ranges: below pH 1.2 it turns red, above pH 2.8 it turns yellow, and below pH 7.4 it turns yellow, above pH 9.0 it turns violet.


References:
  1. Wikipedia contributors. (2021, October 3). Metacresol purple. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.

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Preparation of phenol red indicator solution

Learn the procedure for making phenol red indicator solution.

The compound that change color when exposed to acidic or basic solutions are called indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

How to prepare phenol red indicator for titration:

  • Weigh accurately 100 mg of phenol red and pour it into a 100.00 ml volumetric flask containing 02.82 ml of 0.05N NaOH solution and 20.00 ml of 95% ethanol, warm it.
  • After the solution has been effected, dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 1 g/L.

Phenol red (C19H14O5S) is a synthetic phenolic compound also known as phenolsulfonphthalein or PSP, which acts as a weak acid in a solution. Phenol red exists as a red crystal that is stable in air, it is a water-soluble dye used as an acid pH indicator in different medical and cell biology tests.

Phenol red has a pKa of 8.0 and the pH range is 6.8 to 8.2. In an acidic medium (below pH 6.8) it turns yellow, while in a basic condition (above pH 8.2) it turns bright pink.

Bromothymol blue, thymol blue, bromocresol purple, thymolphthalein, and phenolphthalein are all indicators that have a similar structure to phenol red.



References:
  1. Wikipedia contributors. (2022, January 1). Phenol red. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.
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Wednesday, February 9, 2022

Preparation of bromothymol blue indicator solution

Learn the procedure for making bromothymol blue indicator solution.

The compounds that change color when exposed to acidic or basic solutions are called indicators. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

How to prepare bromothymol blue indicator for titration:

  • Weigh accurately 50 mg of bromothymol blue and pour it into a 100.00 ml volumetric flask containing 04.00 ml of 0.05N sodium hydroxide solution and 05.00 ml of 95% ethanol, warm it.
  • After the solution has been effected, add 45.00 ml of 95% ethanol and dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 0.5 g/L.

Bromothymol blue (C27H28Br2O5S) is also known as bromothymol sulfone phthalein and BTB, which acts as a weak acid in a solution. It used as is a pH indicator and for measuring the presence of carbonic acid in a liquid. BTB is a suitable choice for any titration with a near-neutral equivalence point.

Bromothymol blue has a pKa of 7.1 and the pH range is 6.0 to 7.6. In an acidic medium (below pH 6.0) it turns yellow, while in a basic condition (above pH 7.6) it turns blue, and green in a neutral solution.

Bromothymol blue is prepared by the addition of elemental bromine with thymol blue in a glacial acetic acid solution. It comes in the form of a powder, crystals, or chunks. It might seem yellow or blue depending on whether it is protonated or deprotonated.


References:
  1. Wikipedia contributors. (2022, January 25). Bromothymol blue. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.
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Preparation of methyl red indicator solution

Learn the procedure for making methyl red indicator solution.

The compounds that change color when exposed to acidic or basic solutions are called indicators. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

How to prepare methyl red indicator for titration:

  • Weigh accurately 50.00 mg of methyl red and pour it into a 100.00 ml volumetric flask containing 01.86 ml of 0.1 M sodium hydroxide solution and 05.00 ml of 95% ethanol, warm it.
  • After the solution has been effected, add 45.00 ml of 95% ethanol and dilute to 100.00 ml with distilled water.
  • The concentration of the prepared solution is about 0.5 g/L.

Methyl red (C15H15N3O2), commonly known as C.I. Acid Red 2, is a pH indicator that comes in a dark red crystalline powder. It can be prepared by diazotizing anthranilic acid and then reacting it with dimethylaniline.

It has a pKa of 5.0 and the pH range is 4.2 to 6.2. In an acidic medium (less than 4.4), methyl red turns red, while in a basic condition (higher than 6.2), it turns yellow, and shows orange color in between, with a pKa of 5.1.

Methyl red can be used as an indicator in acid-base titrations involving the strong base and weak acid. It is also used as a dye for the food, leather, and textile industries.



References:
  1. Wikipedia contributors. (2021, November 19). Methyl red. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.
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Preparation of bromocresol green indicator solution

Learn the procedure for making bromocresol green indicator solution.

The compounds that change color when exposed to acidic or basic solutions are called indicators. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

Bromocresol green (C21H14Br4O5S) is a triphenylmethane-based dye. It is a sulfonphthalein, which is a type of dye. It has a pKa of 4.7 and the pH range is 3.8 to 5.4. It commonly dissolves in ethanol or water, but can also be dissolved in benzene and diethyl ether.

How to prepare bromocresol green indicator for titration:

  • Weigh accurately 0.1 g of bromocresol green and pour it into a 100 ml volumetric flask containing 0.58 ml of 0.05 N NaOH solution and 05.00 ml of rectified spirit/ethanol, warm it.
  • After the solution has been effected, add 10.00 ml of rectified spirit/ethanol and dilute to 100 ml with distilled water.
  • The concentration of the prepared solution is about 1 g/L.
Bromocresol green ionizes in an aqueous solution to produce the green monoanionic form (yellow), which deprotonates at higher pH and produces the dianionic form (blue), which is stabilized by resonance.

In an acidic medium (less than 3.8), bromocresol green turns yellow, while in a basic condition (higher than 5.4), it turns green. It's commonly used in strong acid+weak base titration, for electrophoresis, and in microbial growth media.



References:
  1. Law.resource.org. 2022. [online] Available Here:
  2. Wikipedia contributors. (2022, January 5). Bromocresol green. In Wikipedia, The Free Encyclopedia. Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here:
  4. Sabnis, R. W. (2008). Handbook of Acid-Base Indicators. Boca Raton, FL: CRC Press.

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Preparation of methyl orange indicator solution

Learn the procedure for making methyl orange indicator solution.

The compounds that change color when exposed to acidic or basic solutions are called indicators. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

How to prepare methyl orange indicator for titration:

  • Weigh accurately 0.1 g of methyl orange and dissolve in 50 ml of 95% ethanol in a volumetric flask, and properly mix it. Once it has completely dissolved, make up the volume up to 100 ml with ethanol.
  • The concentration of the prepared solution is about 1 g/L.

Methyl orange (C14H14N3NaO3S) is an organic compound that an azo dye prepared from sulfanilic acid and N,N-dimethylaniline. It has a pKa of 4.2 and the pH range is 3.1 to 4.4.

In an acidic medium, methyl orange turns red, while in a basic condition, it turns yellow and in neutral solution it shows orange colour. It's commonly used in acid titration since it changes color at the pKa of a mid-strength acid.

Methyl orange, unlike a universal indicator, does not have a wide range of color changes, however has a sharp end point.

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Tuesday, February 8, 2022

Preparation of methyl yellow indicator solution

Learn the procedure for making methyl yellow indicator solution.

The compounds that change color when exposed to acidic or basic solutions are called indicators. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

How to prepare methyl yellow indicator for titration:

  • Weigh accurately 0.1 g of dimethyl yellow and dissolve in 50 ml of 95% ethanol in a volumetric flask, and properly mix it. 
  • Once it has completely dissolved, make up the volume up to 100 ml.
  • The concentration of the prepared solution is about 1 g/L.

Dimethyl yellow (4-dimethylaminoazobenzene -C6H5N2C6H4N (CH3)2 is an organic compound that an azo dye derived from dimethylaniline used as an acid-base indicator. It has a pKa of 3.3 and the pH range is 2.9 to 4.0.

Methyl yellow shows red in an aqueous solution with a low pH, it undergoes a transition between pH 2.9 and 4.0, turning yellow above pH 4.0. Generally, it is used in the titration of a weak base with a strong acid.



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Preparation of thymol blue indicator solution

Learn the procedure for making thymol blue indicator solution.

The compound that change color when exposed to acidic or basic solutions are called indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.

Most pH indicators are weak acids or bases. For titration, you must select a pH indicator that changes color only at the equivalence point.

How to prepare thymol blue indicator for titration:

  • Weigh accurately 0.1 g of thymol blue and pour it into a 100 ml volumetric flask containing 2.15 ml of 0.05 N NaOH solution and 05.00 ml of 95% ethanol, warm it. 
  • After the solution has been effected, add 25.00 ml of 95% ethanol and dilute to 100 ml with distilled water.
  • The concentration of the prepared solution is about 1 g/L.

Thymol blue (Thymolsulfonephthalein- C27H30O5S) is a crystalline powder that is brownish-green or reddish-brown in color and is used as a pH indicator. It has a pKa of 0.8 and pH ranges of 1.2-2.8 and 8.0–9.6. At pH 1.2–2.8, it changes from red to yellow, while at pH 8.0–9.6, it transitions from yellow to blue.

Thymol blue is a weak acid that is soluble in alcohol and dilute alkali solutions but not in water. It is also usually a component of the universal indicator.


References:
  1. Wikipedia contributors. (2021, December 12). Thymol blue. In Wikipedia, The Free Encyclopedia. Available Here:
  2. Law.resource.org. 2022. [online] Available Here:
  3. Dr John Elfick, j., 2022. Learn how to prepare useful acid-base indicators. Uq.edu.au. Available Here: 
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