Methyl yellow, or C.I. 11020, is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula C₆H₅N₂C₆H₄N(CH₃)₂. It is an

azo dye Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl and substituted aryl groups. They are a commercially important family of azo compounds, i.e. compounds containing the C−N=N−C l ...

derived from

dimethylaniline ''N'',''N''-Dimethylaniline (DMA) is an organic chemical compound, a substituted derivative of aniline. It is a tertiary amine, featuring a dimethylamino group attached to a phenyl group. This oily liquid is colourless when pure, but commercial ...

. It is a yellow solid. According to

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

, the C₁₄N₃ core of the molecule is planar. It is used as a dye for plastics and may be used as a

pH indicator A pH indicator is a halochromism, halochromic chemical compound added in small amounts to a Solution (chemistry), solution so the pH (acidity or Base (chemistry), basicity) of the solution can be determined visually or spectroscopically by chang ...

. In aqueous solution at low pH, methyl yellow appears red. Between pH 2.9 and 4.0, methyl yellow undergoes a transition, to become yellow above pH 4.0.

Safety

It is a possible

carcinogen A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...

. As "butter yellow", the agent had been used as a food additive in butter and margarine before its toxicity was recognized.

History

Butter yellow was synthesized by

Peter Griess Johann Peter Griess (6 September 1829 – 30 August 1888) was an industrial chemist and an early pioneer of organic chemistry. Griess was influential in the formation of modern dyes, first formulating the diazotization reaction of arylamines. Lif ...

in the 1860s at the

Royal College of Chemistry file:The Royal College of Chemistry; the laboratories. Lithograph Wellcome V0013588.jpg, The Royal College of Chemistry: the laboratories. Lithograph The Royal College of Chemistry (RCC) was a college originally based on Oxford Street in central Lo ...

in London. The dye was used to dye butter in

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

and other parts of the world during the latter half of the 19th century and the beginning of the 20th before being phased out in the 1930s and 40s. It was in the 1930s that research led by Riojun Kinosita showed the link between several

azo dyes Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl and substituted aryl groups. They are a commercially important family of azo compounds, i.e. compounds containing the C−N=N−C li ...

and cancer, linking butter yellow to

liver cancer Liver cancer, also known as hepatic cancer, primary hepatic cancer, or primary hepatic malignancy, is cancer that starts in the liver. Liver cancer can be primary in which the cancer starts in the liver, or it can be liver metastasis, or secondar ...

in rats after two to three months exposure. In 1939, the International Congress for Cancer Research issued a recommendation for the banning of cancer-causing food dyes (including butter yellow) from food production. In 2014, dried tofu products such as '' dougan'' (豆乾) from Taiwan were found to have been adulterated with methyl yellow which was used as a coloring agent.

References

External links

* * {{ cite web , url = http://www.inchem.org/documents/iarc/vol08/p-dimethylaminobenzene.html , title = para-dimethylaminoazobenzene , publisher = Inchem
CDC - NIOSH Pocket Guide to Chemical Hazards
PH indicators Azo dyes Anilines IARC Group 2B carcinogens Dimethylamino compounds

Safety

History

See also

References

Further reading

External links