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Methyl Red

Basic information Description Safety Supplier Related

Methyl Red Basic information

Product Name:
Methyl Red
Synonyms:
  • CI NO 13020
  • BROMOCRESOL GREEN-METHYL RED
  • BROMOCRESOL GREEN-METHYL RED ETHANOL
  • BROMOCRESOL GREEN/METHYL RED, MIXED INDICATOR
  • BROMOCRESOL GREEN/METHYL RED, MIX INDICATOR FOR ALKALINITY
  • 2-(4-Dimethylaminophenylazo)benzoic acid, 4-Dimethylaminoazobenzene-2μ-carboxylic acid, Acid Red2
  • METHYL RED
  • METHYL RED INDICATOR
CAS:
493-52-7
MF:
C15H15N3O2
MW:
269.3
EINECS:
207-776-1
Product Categories:
  • BTitration
  • Indicator Solutions
  • Indicators
  • Stains and Dyes
  • Stains&Dyes, A to
  • Titration
  • Biochemical Reagents for Identification
  • Identification Tests&Reagents
  • Microbiology
  • Analytical Chemistry
  • Indicator (pH)
  • pH Indicators
  • Organics
  • Azo
Mol File:
493-52-7.mol
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Methyl Red Chemical Properties

Melting point:
178-182°C
Boiling point:
412.44°C (rough estimate)
Density 
0.839 g/mL at 25 °C
vapor density 
9.3 (vs air)
refractive index 
1.5930 (estimate)
Flash point:
11 °C
storage temp. 
−20°C
solubility 
ethanol: soluble1mg/mL
Colour Index 
13020
form 
Solid
pka
4.95(at 25℃)
color 
Reddish-violet
Odor
Odorless
PH Range
4.4(red)-6.3(yellow)
Water Solubility 
Practically insoluble in water. Soluble in alcohol, acetic acidSoluble in ethanol. Insoluble in water.
λmax
410nm, 530nm, 427nm, 519nm
Merck 
14,6119
BRN 
750102
Stability:
Stable. Incompatible with strong oxidizing agents.
Major Application
Waveguides, LED sensors, photoresists, liquid crystals, sol-gel matrix, optical sensors, paints, toys, detection of thiols, food freshness sensors, dental product, saliva sampling method, detecting lactic acid, carbohydrates
InChIKey
CEQFOVLGLXCDCX-MSUUIHNZSA-N
CAS DataBase Reference
493-52-7
IARC
3 (Vol. 8, Sup 7) 1987
NIST Chemistry Reference
Benzoic acid, 2-[[4-(dimethylamino)phenyl]azo]-(493-52-7)
EPA Substance Registry System
Methyl red (493-52-7)
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Safety Information

Hazard Codes 
Xn,T,F,Xi,C,N
Risk Statements 
10-20/21/22-68/20/21/22-68-36/38-23/25-11-36/37/38-34-51/53-39/23/24/25-23/24/25
Safety Statements 
36/37-24/25-22-45-33-24-16-7-36-26-36/37/39-61
RIDADR 
UN 1170 3/PG 2
WGK Germany 
1
RTECS 
DG8960000
TSCA 
Yes
HazardClass 
3
PackingGroup 
II
HS Code 
29270000
Hazardous Substances Data
493-52-7(Hazardous Substances Data)

MSDS

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Methyl Red Usage And Synthesis

Description

Methyl red is a commonly used indicator for acid-base titrations. This chemical is usually yellow but turns red below pH 4.0. Bacteria exhibiting mixed acids fermentation will accumulate acids in the medium, resulting in a color change. Approximately five drops of methyl red reagent are added to an overnight culture grown in MRVP broth to determine the test result.
Different bacteria convert dextrose and glucose to pyruvate using different metabolic pathways. Some of these pathways produce unstable acidic products which quickly convert to neutral compounds. Some organisms use the butylene glycol pathway, which produces neutral end products, including acetoin and 2,3-butanediol. Other organisms use the mixed acid pathway, which produces acidic end products such as lactic, acetic, and formic acid. These acidic end products are stable and will remain acidic.
The Methyl Red test involves adding the pH indicator methyl red to an inoculated tube of MR-VP broth. If the organism uses the mixed acid fermentation pathway and produces stable acidic end-products, the acids will overcome the buffers in the medium and produce an acidic environment in the medium. When methyl red is added, if acidic end products are present, the methyl red will stay red.

Chemical Properties

dark red crystalline powder

Uses

Used as pH indicator.

Uses

As indicator in 0.1% alcoholic solution; pH: 4.4 red, 6.2 yellow. Used for titrating NH3, weak organic bases, e.g., alkaloids; not suitable for organic acids, except oxalic and picric acid. Methyl red is easily reduced, thereby losing its color, and readings should be made promptly. It is gradually being replaced by sulfonphthalein indicators, such as bromcresol green, which are more stable and exhibit a sharper change in color.

Definition

ChEBI: An azo dye consisting of benzoic acid substituted at position 2 by a 4-[(dimethylamino)phenyl]diazenyl group.

Definition

An acid–base indicator that is red in solutions below a pH of 4.2 and yellow above a pH of 6.3. It is often used for the same types of titration as methyl orange but the transition range of methyl red is nearer neutral (pH7) than that of methyl orange. The two molecules are structurally similar.

Definition

methyl red: An organic dye similarin structure and use to methyl orange.It changes from red below pH4.4 to yellow above pH 6.0 (at 25°C).

Hazard

Questionable carcinogen.

Safety Profile

Questionable carcinogen with experimental tumorigenic data. Mutation data reported. When heated to decomposition it emits toxic fumes of NOx.

Purification Methods

The acid is extracted with boiling toluene using a Soxhlet apparatus. The crystals which separate on slow cooling to room temperature are filtered off, washed with a little toluene and recrystallised from glacial acetic acid, *benzene or toluene followed by pyridine/water. Alternatively, dissolve it in aqueous 5% NaHCO3 solution, and precipitate it from a hot solution by dropwise addition of aqueous HCl. Repeat this until the extinction coefficients do not increase. [Beilstein 16 IV 504.]

Methyl Red Preparation Products And Raw materials

Preparation Products

Raw materials

Methyl RedSupplier

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