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Payment Terms: T/T,L/C,WU 
Place of Origin: Shandong, China (Mainland) 
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Product Detail

Means of Transport: Ocean,Land,Air
Packing: According to the request of...
Brand Name: MOSINTER
Molecular formula: C15H15N3O2
Density: 0.839 g/mL at 25 °C
Storage condition: -20°C
Stability: Stable. Incompatible with s...
Production Capacity: 150 Ton/Year
Delivery Date: within 7 days
CAS No.: 493-52-7
Molecular weight:: 269.3
Melting Point: 178-182°C
Flashing point: 11 °C
Vapour pressure: 2.89E-10mmHg at 25°C

It is an azo dye, and is a dark red crystalline powder.

Methyl Red (CAS: 493-52-7)





Red-brown   powder

PH indication range


Melting point ℃




Flash point ℃


Methyl red (2-(N,N-Dimethyl-4-aminophenyl)azobenzenecarboxylic acid), also called C.I. Acid Red 2, is anindicator dye that turns red in acidic solutions. It is an azo dye, and is a dark red crystalline powder. Methyl red is apH indicator; it is red in pH under 4.4, yellow in pH over 6.2, and orange in between, with a pKa of 5.1. Murexide and methyl red are investigated as promising enhancers of sonochemical destruction of chlorinated hydrocarbon pollutants. Methyl red is classed by the IARC in group 3 - unclassified as to carcinogenic potential in humans.


As an azo dye, Methyl Red may be prepared by diazotization of anthranilic acid, followed by reaction with dimethylaniline:

Methyl Red (CAS: 493-52-7) Methyl red chloride; C.I. Acid Red 2; C.I. Acid Red 2 (8CI); O-Methyl red; CI NO 13020;

Methyl red test

In microbiology, methyl red is used in the Methyl Red (MR) Test, used to identify bacteria producing stable acids by mechanisms of mixed acid fermentation of glucose (cf. Voges–Proskauer (VP) test).

The methyl red test is the "M" portion of the four IMViC tests used to characterize enteric bacteria. The methyl red test is used to identify enteric bacteria based on their pattern of glucose metabolism. All enterics initially produce pyruvic acid from glucose metabolism. Some enteric subsequently use the mixed acid pathway to metabolize pyruvic acid to other acids, such as lactic, acetic, and formic acids. These bacteria are called methyl-red positive and include Escherichia coli and Proteus vulgaris. Other enterics subsequently use the butylene glycol pathway to metabolize pyruvic acid to neutral end-products. These bacteria are called methyl-red-negative and include Serratia marcescens and Enterobacter aerogenes.


An isolate is inoculated into a tube with a sterile transfer loop. The tube is incubated at 35°C for 2–5 days. After incubation, 2.5ml of the medium is transferred to another tube. Five drops of the pH indicator methyl red is added to this tube. The tube is gently rolled between the palms of the hands to disperse the methyl red.

Expected results

Enterics that subsequently metabolize pyruvic acid to other acids lower the pH of the medium to 4.2. At this pH, methyl red turns red. A red color represents a positive test. Enterics that subsequently metabolize pyruvic acid to neutral end-products lower the pH of the medium to only 6.0. At this pH, methyl red is yellow. A yellow color represents a negative test.

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