Murexide
A purple chemical once used as a dye and indicator in chemistry
No single value: Murexide is a material, and its colour varies. The background shows its family, purple and violet.
Murexide is a purple solid, the ammonium salt of purpuric acid, and dissolves in water. Its colour shifts from yellow in acidic solutions to blue-purple in alkaline ones. First made from guano in the 1850s, it was used as a dye and as an indicator in chemical analysis, especially for calcium.
- Turns yellow in acid and blue-purple in alkali
- First made from guano in the 1850s
- Used as a dye and chemical indicator
- Studied in Germany and France
What colour is Murexide?
Murexide is a synthetic purple compound that forms a solid, dissolving easily in water. Its appearance changes with acidity: yellow in strong acid, reddish-purple in weak acid, and blue-purple in alkaline conditions. This shifting colour made it useful in chemical tests. It is also known as ammonium purpurate.
Where does Murexide come from?
The compound was first studied in the 1830s in Giessen, Germany, by Justus von Liebig and Friedrich W枚hler, who obtained it from snake excrement. However, this source was not practical for large-scale use. In the 1850s, French chemists found a way to make it from South American guano, which allowed wider use, especially in Britain, France, and Germany.
How is Murexide made?
Murexide can be made by heating alloxantin with ammonia, or by treating uramil (a chemical related to barbituric acid) with mercury oxide. Another method uses alloxan and alcoholic ammonia. In the 19th century, guano was a common raw material for its production.
Where Murexide is used
Murexide was used as a dye for natural fibres and in printing, especially after the 1850s. In chemistry, it served as an indicator for measuring metal ions like calcium, copper, and nickel in solutions. Its use in chemical analysis has now been mostly replaced by more modern methods.
Purple around the world
What the purple and violet family means from country to country.
In Holy Week, members of religious brotherhoods walk in procession in robes and pointed hoods, many of them purple, the colour of penance. A purple band also marked the flag of the Second Republic.
Sacred and holyPolitics and protestSource: Holy Week in SpainSuffragettes campaigning for women's votes wore purple, white and green: purple for dignity, white for purity and green for hope.
Politics and protestCourageSource: SuffragetteA child born to a reigning Byzantine emperor was called porphyrogennetos, born in the purple. The birth took place in a palace room lined with purple stone.
Royalty and powerAweSource: Born in the purpleIn the elections of 2005, voters dipped a finger in purple ink to prevent double voting. The stained finger, held up for cameras, became a sign of the vote.
Politics and protestPrideSource: Election inkPurple dye from the murasaki plant was costly and hard to make. In the court rank system set up under Prince Shotoku, the highest officials wore purple caps.
Royalty and powerAweSource: Twelve Level Cap and Rank SystemThe Phoenician cities of Tyre and Sidon made Tyrian purple from sea snails. The dye was so costly that it became the colour of kings and Roman emperors.
Royalty and powerAweSource: Tyrian purpleShades and relatives of Murexide
Murexide solutions show different colours depending on the pH, ranging from yellow to blue-purple. It is sometimes confused with other purple dyes, but its chemical behaviour and colour changes set it apart.
Questions people ask about Murexide
What colour is murexide?
Murexide is a purple solid. In water, its colour changes: yellow in strong acid, reddish-purple in weak acid, and blue-purple in alkaline solutions.
Where does the name murexide come from?
The sources do not explain the origin of the name 'murexide'.
How was murexide first made?
It was first studied in the 1830s from snake excrement, but large-scale production began in the 1850s using guano, especially in France.
What was murexide used for?
Murexide was used as a dye for natural fibres and as a chemical indicator in analytical chemistry, mainly for detecting calcium and other metal ions.
Is murexide still used today?
Its use as a chemical indicator has mostly been replaced by more modern methods, such as calcium-ion selective electrodes.
Good reading and sources
The facts on this page come from the Wikipedia article "Murexide", 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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