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From fashion to science: Why did Congo red cause a sensation in the dye world but then quickly fade away?
Congo red, a bright organic pigment, sparked a revolution in the dye world at the end of the 19th century. However, over time, its luster faded and was replaced by concerns about its cancer risk. This article will explore the history, characteristics and applications of Congo red in various fields, and consider why its glory was so short-lived.
The birth and commercial success of Congo Red
Congo red was synthesized in 1883 by Paul Böttiger, who aimed to develop a dye that did not require a mordant. Initially, his employer was not interested in the bright red color, so Bottig filed the patent in his own name and sold it to AGFA on Main.
AGFA subsequently promoted the dye under the resounding name "Congo Red", a name that in Germany at the time was inseparable from the historical background of the 1884 West African Conference in Berlin. This conference was an important event in the colonization of Africa. With its commercial success, other dyes also took the name "Congo", such as Congo orange, Congo blue, etc.
Chemical properties of Congo red
Congo red is a water-soluble dye with the chemical structure 3,3′-([1,1′-diphenyl]-4,4′-diyl)bis(4-aminonaphthalene-1- Sulfonic acid) sodium salt. Its solubility is higher in organic solvents, forming a red colloidal solution. Congo red exhibits a color change from blue to red when the pH is between 3.0 and 5.2, making it a pH indicator.
Medical and scientific applications of Congo red
Congo red’s uses are not limited to dyes. Today, it is still important in histology and microscopy, and is particularly common in the detection of Amilian disease, since the birefringence of apple-green under polarized light indicates the presence of amyloid fibrils.
In addition, Congo Red can also be used to detect the special structure of bacteria, especially Salmonella, and is used to detect Acamania in flow cytometry experiments.
In addition, Congo red is also used as a stable fluorescent dye in analytical microscopy, showing its potential in biomedical research.
Descending destiny and present taboos
Although Congo Red was once popular, the dye was gradually marginalized by the industry as awareness of its cancer risk increased. Many aniline-derived dyes were phased out due to their potential health risks, resulting in a significant decline in the use of Congo red. Today, its presence is found more in scientific laboratories than in the fiber industry.
Continued use of Congo blue
Although Congo red is no longer the mainstream choice for industrial dyes, its close relative, Congo blue, is still widely used in many fields, especially as a lighting filter in live concerts and film and television performances. This color filter can create deep blues and produce different visual effects under different colors of light.
The unique properties of Congo Blue make it a powerful tool for lighting technicians, especially when adjusting brightness and contrast, fully demonstrating the importance of color in visual arts.
Looking to the future and thinking
The story of Congo Red is not only a change in technology, but also a reflection of society’s understanding and attitude towards chemical substances. As new materials are developed, will future dyes be safer and more harmless? What innovative alternatives will advances in science bring about that will allow us to use color more safely to enhance the quality of our lives?
