Simagchem Corp.

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. The solution is dark blue when in sulfuric acid, turning to light blue accompanied with the appearance of blue precipitate when diluted.

Its aqueous solution will form a blue floc when in concentrated hydrochloric acid. When added with acetic acid, the precipitate turned blue with a little purple to a precipitate with some red color. It is insoluble in the concentration of caustic soda solution; susceptible to acid and salt which means even if its absorption of carbon dioxide from the air will make the color blue and dark, while dilute soda solution can restore the original color.

Information on the chemical properties, uses and production methods of artificial dyes Congo Red is compiled and edited by Chemcialbook.

Uses 1. It has been widely used in cotton, viscose dyeing. Because it can easily be transformed into blue when in acid, while there is no appropriate treatment to improve, the usage amount is gradually decreased since the advent of insoluble azo dyes and acid-resistant red 4BS, however, the amount used in the paper industry is quite large. It can also be used as indicators of acid-base, namely Congo red test paper. The measurable range pH is 3.0 (blue)-5.0 (red). It is also used for biological staining, analysis reagents.

2. An indicator frequently used in lab as well as a carcinogenic disperse dyes; used to standard test.

3. Used as an acid-base indicator, adsorption indicator and biological stain, etc.

4. Acid-base indicator, pH 3.0 (blue violet)~5.0 (red); detect the acidity of paper and hydrochloric acid in the gastric juice; test boric acid, cyanide; biological media additives; biological staining, such as embryo slices, plant mucin, cellulose, elastic tissue dyeing.

5. Mainly used for dyeing cotton, hemp, silk and other textile and paper products; it can also be used as an indicator.