Methyl orange
An orange-red azo dye used as a pH indicator in chemistry
Methyl orange is a synthetic dye that serves as a pH indicator, shifting from red in acidic solutions to yellow in alkaline ones. Its sharp colour change makes it valuable for measuring acidity in chemical titrations, especially when testing strong acids against weak bases.
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- Turns red in acid and yellow in base
- Used to measure acidity in chemical titrations
- Made from dimethylaniline and sulfanilic acid
- Absorbs green-cyan light, appears orange
- Can break down into harmful compounds
What colour is Methyl orange?
Methyl orange is a man-made dye that acts as a chemical indicator, changing colour depending on the acidity of a solution. In acidic conditions, it appears red, while in alkaline (basic) solutions, it turns yellow. The colour shifts through orange as the acidity lessens. Its clear and quick transition between these colours makes it useful for pinpointing when a chemical reaction has reached a certain point.
Where does Methyl orange come from?
This dye is a type of azobenzene compound, created in the laboratory from dimethylaniline and sulfanilic acid. The name 'methyl orange' comes from its chemical structure and the bright orange shade it displays in neutral conditions. It does not have a traditional or natural origin, but is entirely synthetic.
How is Methyl orange made?
Methyl orange is produced by combining dimethylaniline and sulfanilic acid. First, sulfanilic acid is converted into a diazonium salt, which then reacts with dimethylaniline. The process forms an azo bond, resulting in the final dye. This compound absorbs light mainly in the green-cyan part of the spectrum, which is why it appears orange to the eye.
Where Methyl orange is used
Chemists use methyl orange mainly to measure acidity in solutions, especially during titrations that involve strong acids and weak bases. Its sharp colour change helps identify when the reaction is complete. It is not used for general colouring purposes, but its clear shift between red, orange, and yellow is valuable in laboratory work.
Orange around the world
What the orange family means from country to country.
The lowest band of the flag is orange, often called apricot, after the national fruit. The constitution says it stands for the creative talent and hard work of the people.
Politics and protestNature and renewalPrideSource: Flag of ArmeniaThe flag is split corner to corner. The orange half stands for the Buddhist tradition, and the white dragon across the middle for purity.
Sacred and holySource: Flag of BhutanOn 30 September people wear orange shirts to remember the children sent to residential schools. Phyllis Webstad's new orange shirt was taken from her on her first day at one.
Mourning and deathPolitics and protestGriefSource: National Day for Truth and ReconciliationOrange is also the colour of the New Democratic Party. Its sweep of Quebec seats in the 2011 election was called the Orange Wave.
Politics and protestSource: New Democratic PartyThe flag shows the island in copper orange on white. The colour recalls copper, which was mined here in ancient times and may have taken its name from Cyprus.
Politics and protestNature and renewalSource: Flag of CyprusThe orange stripe of the flag stands for Protestants, the followers of William of Orange. In Northern Ireland the Orange Order still marches each 12 July in orange sashes.
Politics and protestSource: Orange OrderShades and relatives of Methyl orange
A modified version called screened methyl orange is made by mixing methyl orange with xylene cyanol. This blend changes from a greyish violet to green as the solution becomes more alkaline, offering a different visual cue for chemical tests.
Colours that go with Methyl orange
Harmonies are worked out from the value #E32600. Contrast ratios follow the WCAG 2 formula.
Questions people ask about Methyl orange
What colour is methyl orange?
Methyl orange is orange in neutral solutions, shifts to red in acidic conditions, and turns yellow in alkaline solutions.
Where does the name methyl orange come from?
The name comes from its chemical structure, which includes a methyl group and its orange colour in solution.
How is methyl orange made?
It is synthesised in the lab by reacting dimethylaniline with sulfanilic acid, forming an azo dye.
What is methyl orange used for?
It is mainly used as a pH indicator in chemical titrations to detect changes in acidity.
Is methyl orange safe?
Methyl orange can break down into substances that may cause mutations or cancer, so it should be handled with care.
Good reading and sources
- Methyl orange on WikipediaEncyclopedia
- More pictures on Wikimedia CommonsPictures
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Methyl orange", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). Rang rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes. The swatch is an approximation: named colours are not fixed standards, and every screen shows them a little differently. If something is wrong, tell us. Last refreshed 2026-10-03.
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