What does Congo red dye do?
Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing. It is still used in histology to stain tissues for microscopic examination, and to serve as an acid-base indicator, since it turns red in the presence of alkalies and blue when exposed to acids.
Is Congo red natural dye?
It is an azo dye. Congo red is water-soluble, yielding a red colloidal solution; its solubility is greater in organic solvents. However, the use of Congo red has long been abandoned, primarily because of its carcinogenic properties….Behavior in solution.
| Congo red (pH indicator) | ||
|---|---|---|
| below pH 3.0 | above pH 5.2 | |
| 3.0 | ⇌ | 5.2 |
How do you make a 1% Congo red solution?
Congo Red powder dye solution (for staining acc. to the Highman method): 1% solution of Congo Red powder dye: • Dissolve 0.5 g of Congo Red dye in 50 ml of distilled/demi water. Add 50 mL of 100% ethanol.
Is Congo red a mordant dye?
Congo red is a synthetic dye, used for the differential staining of elastic fibers. Congo red histological staining is the gold standard technique for the detection of amyloidosis. It is a dye belongs to a group of azo dyes derived from benzidine and it does not require the application of mordant.
Is Congo red harmful?
We determined that Congo Red is highly toxic to C. dubia since it inhibits survival and fertility in concentrations exceeding 3 mg L-1. Our results show that this dye produces negative effects at very low concentrations.
Is Congo red dye carcinogenic?
For instance, the diazo dye Congo red is known to be carcinogenic because of the presence of aromatic amine groups [9].
Is Congo red carcinogenic?
Congo Red is an azo dye, it is toxic to many organisms and is a suspected carcinogen and mutagen.
How Congo red dye is prepared?
Congo Red is synthesised by coupling bis-diazotised benzidine with two molecules of napthionic acid. The blue dye so obtained is converted into its red disodium salt during its salting out with sodium chloride (Fig.
Why is it called Congo red?
Conclusions: The Congo red stain was named “Congo” for marketing purposes by a German textile dyestuff company in 1885, reflecting geopolitical current events of that time.
Is Congo red a azo dye?
Abstract. Congo red is one of the best known and used azo dyes which has two azo bonds (-N=N-) chromophore in its molecular structure. Its structural stability makes it highly toxic and resistant to biodegradation.
Is Congo red hazardous?
Skin: May cause skin irritation. May cause skin sensitization, an allergic reaction, which becomes evident upon re-exposure to this material. May cause skin irritation and possible burns. Ingestion: May cause gastrointestinal irritation with nausea, vomiting and diarrhea.
How is Congo red made?
Congo Red is synthesised by coupling bis-diazotised benzidine with two molecules of napthionic acid. The blue dye so obtained is converted into its red disodium salt during its salting out with sodium chloride (Fig. 4.2).
What type of stain is Congo red?
Congo red demonstrates the accumulation of amyloid. With light microscopy it stains a pink or light red colour and shows green birefringence with polarized light. With rhodamine or Texas fluorescence the deposits show enhanced red fluorescence.
Is Congo red toxic?
Congo Red is an azo dye, it is toxic to many organisms and is a suspected carcinogen and mutagen. To give it its full name it is the disodium salt of 3,3′-(1E,1’E)-biphenyl-4,4′-diylbis(diazene-2,1-diyl)bis(4-aminonaphthalene-1-sulfonate).
Is Congo Red carcinogenic?
Is Congo red used in textile industry?
The azo dyes (Congo red), a main class of synthetic colourants, are usually used in the textile manufacturing due to their properties, such as a large variety of shades, resistance to decolouring, and a lower energy consumption2.
Is Congo red an acidic dye?
Congo red is an acid-base indicator dye. In free solution the colour and absorption characteristics of Congo red depend not only on the pH but are also governed by the nature of the solvent environment.
Is Congo red dye still used today?
However, the use of Congo red has long been abandoned, primarily because of its carcinogenic properties. Congo red was first synthesized in 1883 by Paul Böttiger, who had been employed at Friedrich Bayer Company in Elberfeld, Germany. He was looking for textile dyes that did not require a mordant step.
What is the solubility of Congo red?
Congo red is water-soluble, yielding a red colloidal solution; its solubility is greater in organic solvents. However, the use of Congo red has long been abandoned, primarily because of its carcinogenic properties.
How do you make Congo red?
It is prepared by azo coupling of the bis (diazonium) derivative of benzidine with naphthionic acid . Due to a color change from blue to red at pH 3.0–5.2, Congo red can be used as a pH indicator.
What is Congo red good for?
One of the most common applications of Congo red is its usefulness in the diagnosis of amyloidosis. This strange disease consists of the extracellular accumulation of an abnormal protein in various organs. This abnormal protein is made in the bone marrow and is called amyloid.