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Is Congo red a pH indicator?
“Congo red” is not the name of a famous African explorer, but a dye that dates to 1883. It was synthesized by P. Böttiger as a textile dye, but it subsequently became more important as a pH indicator. It colors aqueous solutions blue below pH 3.0 and becomes red above pH 5.0.
Why Congo Red is used as acid-base indicator?
Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing.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 a basic dye?
Congo Red is an acid-base indicator dye. Such solvents may also change the aggregation or solvation states of the dye, with consequent modification in the colour of tissue components.
What color is Congo?
Congo Green is a deep, pure, peacock green with a seafoam undertone. It is a perfect paint color for all the walls of a dining room or living room or an accent wall. Pair it with fresh yellows and lively pinks for a South-of-the-Border appeal.
What color does Congo red stain?
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.
What is the formula of Congo red?
C32H22N6Na2O6S2
Congo red/Formula
What Colour is the Congo flag?
yellow
flag of the Democratic Republic of the Congo. national flag consisting of a blue field (background) with a yellow-bordered red diagonal stripe running from the lower hoist to the upper fly corner and, in the upper hoist corner, a yellow star. The flag’s width-to-length ratio is 2 to 3.
What is Congo red soluble in?
Chemical properties Congo red is red-brown powder, soluble in hot water and the cold water 10 times of its weight; the color of the solution is yellow-red; soluble in ethanol and the solution is orange; slightly soluble in acetone, while almost insoluble in ether.
What is the behavior of Congo red in a solution?
Behavior in solution. Due to a color change from blue to red at pH 3.0–5.2, Congo red can be used as a pH indicator. Since this color change is an approximate inverse of that of litmus, it can be used with litmus paper in a simple parlor trick: add a drop or two of Congo red to both an acid solution and a base solution.
What is the formula for Congo red?
Congo red is the sodium salt of benzidinediazo-bis-1-naphtylamine-4-sulfonic acid (formula: C 32 H 22 N 6 Na 2 O 6 S 2; molecular weight: 696.66 g/mol). It is a secondary diazo dye. Congo red is water soluble, yielding a red colloidal solution; its solubility is better in organic solvents such as ethanol.
What is congcongo red indicator dye?
Congo Red is an indicator dye that is blue-violet at pH 3.0 and red at pH 5.0. It contains a 3,3′-(biphenyl-4,4′-diyldidiazene-2,1-diyl)bis(4-aminonaphthalene-1-sulfonate). It derives from a 3,3′-(biphenyl-4,4′-diyldidiazene-2,1-diyl)bis(4-aminonaphthalene-1-sulfonic acid).
Is Congo red dye soluble in water?
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.