Methyl Red#493-52-7

Distinctive appearance – Methyl Red is available as lustrous purple crystals or reddish-brown powder.
Selective solubility – Insoluble in water but dissolves readily in ethanol, chloroform, and acetic acid.
Reliable pH indicator – Widely used in acid-base titrations to indicate solution pH.
Accurate endpoint detection – Helps determine titration endpoints through clear color changes.

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Product Details

Methyl Red #493-52-7

Methyl Red typically appears as lustrous purple crystals or a reddish-brown powder. It is nearly insoluble in water but dissolves easily in ethanol, chloroform, and acetic acid. The compound is primarily used as a pH indicator in acid-base titrations, allowing for precise determination of the titration endpoint through visible color changes.

Methyl Red#493-52-7

Methyl Red Chemical Properties

Melting point	179-182 °C (lit.)
Boiling point	412.44°C (rough estimate)
density	0.839 g/mL at 25 °C
bulk density	300-500kg/m3
vapor density	9.3 (vs air)
refractive index	1.5930 (estimate)
Fp	11 °C
storage temp.	Store at +5°C to +30°C.
solubility	ethanol: soluble1mg/mL
form	Solid
pka	4.95(at 25℃)
Colour Index	13020
color	Reddish-violet
PH Range	4.4(red)-6.3(yellow)
Odor	Odorless
Water Solubility	Practically insoluble in water. Soluble in alcohol, acetic acidSoluble in ethanol. Insoluble in water.
λmax	410nm, 530nm, 427nm, 519nm
ε(extinction coefficient)	≥10000 at 282-288nm in methanol
	≥20000 at 509-519nm in methanol
	≥7000 at 329-335nm in methanol
Merck	146119
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
NIST Chemistry Reference	Benzoic acid, 2-[[4-(dimethylamino)phenyl]azo]-(493-52-7)
IARC	3 (Vol. 8, Sup 7) 1987
EPA Substance Registry System	Methyl red (493-52-7)

Methyl Red#493-52-7

Product Usage

Methyl Red is used as an indicator in a 0.1% alcoholic solution, showing red at pH 4.4 and yellow at pH 6.2. It is suitable for titrating ammonia and weak organic bases, such as alkaloids, but is not recommended for most organic acids, except oxalic and picric acid. Methyl Red can be easily reduced, causing a loss of color, so readings should be taken promptly. It is increasingly being replaced by more stable sulfonphthalein indicators, such as bromcresol green, which provide a sharper color change.

Methyl Red#493-52-7