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

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

with the formula C₆H₅N₂C₆H₄N(CH₃)₂. It is an azo dye derived from

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

. It is a yellow solid. According to

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

, 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 halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. Hence, ...

. 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 substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...

. 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. Li ...

in the 1860s at the

Royal College of Chemistry The Royal College of Chemistry: the laboratories. Lithograph The Royal College of Chemistry (RCC) was a college originally based on Oxford Street in central London, England. It operated between 1845 and 1872. The original building was designed ...

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 is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

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 ...

and cancer, linking butter yellow to liver cancer 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 (a.k.a. '' dougan'' 豆乾) from Taiwan were found to have been adulterated with methyl yellow, 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

Safety

History

See also

References

Further reading

External links