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Methyl Orange Chemical Structure

What is Methyl Orange?

Methyl Orange is a synthetically derived organic azo dye. It shows red color in acidic medium (below pH 3.1) and yellow color in basic medium (above pH 4.4) and is thus often used as a pH indicator in laboratory experiments and other various applications to monitor pH changes.

Macsen Laboratories is the leading manufacturer and supplier of Methyl Orange dye with ISO certification.
Name of Product Methyl Orange
IUPAC Name sodium;4-[[4-(dimethylamino)phenyl]diazenyl]benzenesulfonate
Synonyms Orange III; MethylOrange; Gold Orange; Helianthine B; C.I. Acid Orange 52; Eniamethyl Orange; Tropaeolin D; Sodium p-dimethylaminoazobenzenesulfonate
CAS No 547-58-0
Molecular Formula C14H14N3NaO3S
Molecular Weight 327.34 g/mol
Pubchem CID 23673835


SR. No Criteria Limit/Specification
1 Appearance (form) Crystalline Solid Powder
2 Appearance (color) Orange-Yellow
3 Solubility Soluble in water (5 g/L) and organic solvents
Insoluble in diethyl ether and alcohol
4 Melting Point 300℃ (572 °F; 573 K)
5 Density 1.28 g/cm3
6 pKa 3.47

How does methyl orange indicator work?

Methyl Orange is a pH indicator that works by undergoing a color change in response to the acidity or alkalinity of a solution. In an acidic environment, it appears red, while in an alkaline environment, it turns yellow. This color shift is due to the molecule’s structure, which changes in response to variations in pH, making it a valuable tool for determining pH levels in various chemical and biological applications.


  • pH Testing: Methyl Orange is used to determine the acidity or alkalinity of a solution, making it valuable for quality control and analytical chemistry.
  • Titration Indicator: It’s employed in acid-base titrations to signal the endpoint when the pH reaches a specific value, helping in precise measurements.
  • Wastewater Monitoring: Methyl Orange is used to assess the pH of industrial and environmental wastewater, ensuring compliance with regulations.
  • Textile and Leather Industry: It’s used to monitor and control pH during dyeing and finishing processes in these industries.


Q. Does methyl orange dissolve in water?

Methyl Orange is soluble in water.

Q. How to prepare methyl orange indicator?

Methyl Orange indicator solution can be prepared by dissolve 0.1 g of methyl orange in 80 ml of water followed by addition of  sufficient ethanol (95 %) to produce 100 ml.

Q. Is methyl orange acidic or basic?

Methyl Orange is a weak acid.

Q. Is methyl orange polar?

Methyl Orange is a polar molecule. It contains polar covalent bonds due to differences in electronegativity between the atoms in the molecule.

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