Basic information Artificial dyes Chemical properties Uses Production methods Safety Supplier Related
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Congo Red

Basic information Artificial dyes Chemical properties Uses Production methods Safety Supplier Related

Congo Red Basic information

Product Name:
Congo Red
Synonyms:
  • 3,3'-[(1,1'-BIPHENYL)-4,4'-DIYLBIS(AZO)]BIS(4-AMINO-1-NAPHTHALENESULFONIC ACID) 2NA
  • S NO 360
  • CONGO RED (CERT)
  • Congo Red (0.1% in Water) [for pH Determination]
  • 3,3'-[(Biphenyl-4,4'-diyl)bisazo]bis(4-amino-1-naphthalenesulfonic acid sodium) salt
  • 3,3'-[[1,1'-Biphenyl]-4,4'-diylbis(azo)]bis[4-amino-1-naphthalenesulfonic acid sodium] salt
  • Congo Ared 4b
  • Congo Red K
CAS:
573-58-0
MF:
C32H22N6Na2O6S2
MW:
696.66
EINECS:
209-358-4
Product Categories:
  • Azo
  • Dyes and Pigments
  • Organics
  • Analytical Chemistry
  • Indicator (pH)
  • pH Indicators
Mol File:
573-58-0.mol
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Congo Red Chemical Properties

Melting point:
>360 °C(lit.)
Density 
0.995 g/mL at 25 °C
vapor pressure 
<1 Pa
storage temp. 
Flammables area
solubility 
H2O: soluble10mg/mL
Colour Index 
22120
pka
4.1(at 25℃)
form 
Powder/Solid
color 
Red Brown
Odor
Odorless
PH
6.7 (10g/l, H2O, 20℃)
PH Range
3(blue)-5.2(red)
Water Solubility 
soluble
λmax
497nm, 488nm, 595nm
Merck 
14,2498
BRN 
3894858
Stability:
Stable. Incompatible with strong oxidizing agents.
Biological Applications
Detecting bacteria,protein folding disorders; treating dermatological disorders,neurodegenerative diseases,Alzheimer’s disease
Major Application
Waveguides, optical sensors, display devices, inks, fertilizer, pesticides, carbohydrates, treatment of pathogen infections, age-related macular degeneration
CAS DataBase Reference
573-58-0(CAS DataBase Reference)
EPA Substance Registry System
Congo Red (573-58-0)
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Safety Information

Hazard Codes 
T,Xi
Risk Statements 
45-63-36
Safety Statements 
53-45-37/39-26
RIDADR 
2811
WGK Germany 
3
RTECS 
QK1400000
TSCA 
Yes
PackingGroup 
II
HS Code 
29215900
Hazardous Substances Data
573-58-0(Hazardous Substances Data)
Toxicity
LD50 i.v. in rats: 190 mg/kg (Richardson, Dillon)

MSDS

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Congo Red Usage And Synthesis

Artificial dyes

Congo red is aniline dye or coal tar dyes, and it has many types with very wide application. Its drawback is easy to fade by sunlight; aniline blue, bright green, methyl green are more easily fade. Be careful to handle the pH, and avoid direct sunlight when flaking, thus it will keep a few years without fading.
Congo red is an acid dye, a purplish red powder. It is soluble in water and alcohol, turning blue when in acid. It can be used as a dye as well as an indicator. In the production of plant slide, it is often used as a liner agent for hematoxylin or other cell dyes. When used in cytoplasm dyes, it can dye the cytosol or fibrin red. In the process of tissue slicing, it is used to dye nerve axis, elastic fibers, embryonic materials, etc. In addition, Congo red can be used for double staining with hematoxylin; it can also be used for amyloid staining. For it is soluble in water and alcohol, so washing and dehydration treatment should be quick.

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.

Production methods

It is obtained by the coupling with  sodium naphthionate after the diazotization with benzidine, and then by salting out, filtration and drying in the system. The details are as follows: add 48.4 benzidine into 300ml of hydrochloric acid take 48.4g benzidine dissolved in 300ml hydrochloric acid (including 20ml of concentrated hydrochloric acid 20ml), add ice into the solution until the temperature is below 5 ℃; add 10% aqueous solutions prepared by 14.4g sodium nitrite after adding 30ml of concentrated hydrochloric acid.Add the diazonium salt solution slowly into the solution prepared by 150g sodium naphthionate and a little water after diazotization. Add 35g sodium carbonate slowly under the sufficient mixing after 30 minutes' standing, thus appearing an alkaline solution. Heating to 80℃, cooling, filtering, washing with saturated brine and drying can obtain the product. The materials consumption (kg/t) in industrial production are as follows: benzidine (100%) 200, sodium naphthionate (100%) 520, sodium nitrite (industry) 160, hydrochloric acid (31%) 330, soda ash (industrial) 340, fine salt 2500, turkey red oil 9, ethanol 60, sodium acetate 35, sodium sulfate 50.

Chemical Properties

brown-red powder

Chemical Properties

C.I. Direct red 28(Congo Red) is an odorless, brownish-red powder.

Uses

Dye, medicine (diagnostic aid), indicator, biological stain.

Definition

ChEBI: An indicator dye that is blue-violet at pH 3.0 and red at pH 5.0.

Safety Profile

Human poison by ingestion with cardovascular effects. Experimental poison by intravenous route. An experimental teratogen. Experimental reproductive effects. An eye irritant. Mutation data reported. When heated to decomposition it emits very toxic fumes of NOx, SOx, and Na2O

Potential Exposure

It is used as an indicator dye, a biological stain; a diagnostic aid in medicine; and a dye for fabric and paper.

Shipping

UN3143 Dyes, solid, toxic, n.o.s. or Dye intermediates, solid, toxic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required

Purification Methods

Crystallise the dye from aqueous EtOH (1:3). Dry it in air. [Beilstein 6 I 342.]

Incompatibilities

Contact with oxidizers may cause fire and explosion hazard. Incompatible with strong acids; reducing agents.

Congo RedSupplier

J & K SCIENTIFIC LTD.
Tel
010-82848833- ;010-82848833-
Email
jkinfo@jkchemical.com;market6@jkchemical.com
Products Intro
Product Name:Congo Red, indicator
CAS:573-58-0
Package:100G;25G
Meryer (Shanghai) Chemical Technology Co., Ltd.
Tel
21-61259100-
Email
sh@meryer.com
Products Intro
Product Name:Congo Red
CAS:573-58-0
Purity:>98.0%(LC) Package:25g Remarks:C0550
3B Pharmachem (Wuhan) International Co.,Ltd.
Tel
821-50328103-801
Email
3bsc@sina.com
Products Intro
Product Name:Direct Red 28
CAS:573-58-0
Purity:99% HPLC Package:1Mg ; 5Mg;10Mg ;100Mg;250Mg ;500Mg ;1g;2.5g ;5g ;10g
future industrial shanghai co., ltd
Tel
400-0066-400;021-60496031
Email
sales@jonln.com;sales@jonln.com
Products Intro
Product Name:Congo red
CAS:573-58-0
Purity:AR Package:597RMB/ 500g
Alfa Aesar
Tel
400-610-6006; 021-67582000
Email
saleschina@alfa-asia.com
Products Intro
Product Name:Congo Red, indicator grade
CAS:573-58-0
Package:25g Remarks:B24310