Formazan
A group of synthetic dyes with colours from dark blue to deep red or orange
No single value: Formazan is a material, and its colour varies. The background shows its family, blue.
Formazans are artificial dyes made by reducing tetrazolium salts, producing colours that range from dark blue to deep red or orange. Their intense hues and chemical reactivity make them useful in laboratory tests, especially for detecting living cells.
- Formazans are intensely coloured synthetic dyes
- They are made by reducing tetrazolium salts
- Their colours range from dark blue to deep red or orange
- Used in laboratory tests for living cells
- Structure first defined in 1892
What colour is Formazan?
Formazans are a group of synthetic compounds known for their strong, vivid colours, which can range from dark blue to deep red and orange. They are closely related to azo dyes and have a nitrogen-rich backbone, which gives them their intense colour and chemical reactivity. Their structure allows them to form several isomeric shapes and to react with both acids and bases.
Where does Formazan come from?
The structure of formazans was first described in 1892 by von Pechmann and independently by Bamberger and Wheelwright. The name formazan refers to their chemical structure, which is not found in nature but is created in laboratories. They are produced by reducing tetrazolium salts, a process discovered through studies of chemical reactions involving nitrogen compounds.
How is Formazan made?
Formazans are made synthetically, usually by reacting diazonium compounds with hydrazones or active methylene compounds. Another method involves oxidising hydrazidines, which are themselves made from hydrazonyl halides and hydrazine derivatives. Formazans can also be formed by breaking down substituted tetrazolium salts, either with light or with ascorbic acid in an alkaline solution.
Where Formazan is used
Formazan dyes are mainly used in laboratory settings, especially in colour-based tests that show whether cells are alive. When tetrazolium salts are reduced inside living cells, they turn into formazans, which are brightly coloured and easy to see. This property is used in cell viability and toxicity assays, where only living cells produce the dye.
Blue around the world
What the blue family means from country to country.
Lapis lazuli has been mined in the mountains of Badakhshan for more than six thousand years. Ground to powder it gave ultramarine, the costliest blue in European painting.
Royalty and powerSacred and holyAweSource: Lapis lazuliThe chadari is a full-length covering for women with a mesh panel over the eyes. In Kabul and the north it is most often a light blue.
Protection and healingSource: BurqaThe blue band of the flag stands for the wish of the Armenian people to live under peaceful skies. The red above it is for the highlands and the struggle to survive.
Politics and protestHopeSource: Flag of ArmeniaThe flag is sky blue, white and sky blue, created by Manuel Belgrano in 1812. National teams are called the Albiceleste, the white and sky blue.
Politics and protestPrideSource: Flag of ArgentinaBoca Juniors play in blue and gold. The club's story is that in 1907 it took the colours of the flag of the next ship into port, which was Swedish.
Festival and celebrationPrideSource: Boca JuniorsTo be true blue is to be honestly and loyally Australian. The phrase is older than the country, but Australians have made it their own.
Politics and protestTrustSource: True Blue (John Williamson song)Shades and relatives of Formazan
Formazans can appear in a range of colours, from dark blue to deep red and orange, depending on the tetrazolium salt used to make them. They exist in several isomeric forms due to their flexible structure. Different formazan dyes, such as those from MTT or XTT assays, may have different solubility and colour.
Questions people ask about Formazan
What colour are formazans?
Formazans can be dark blue, deep red, or orange, depending on the chemical process and starting materials used to make them.
Where does the name formazan come from?
The name formazan refers to their chemical structure, which is based on a nitrogen-rich backbone. The structure was first described in 1892.
How are formazans made?
Formazans are made synthetically, usually by reducing tetrazolium salts or by reacting diazonium compounds with hydrazones or active methylene compounds.
What are formazans used for?
Formazans are mainly used in laboratory tests to show if cells are alive, as they form brightly coloured dyes inside living cells.
Good reading and sources
The facts on this page come from the Wikipedia article "Formazan", 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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