Product Overview
Methyl Red (CAS#493-52-7) is a synthetic azo dye compound commonly used as an acid-base indicator in chemical analysis. It is recognized for its excellent color response and reliable performance in titration experiments.
The compound displays a noticeable color transition as the pH value changes, making it particularly useful for acid-base titration endpoint determination. Its stable chemical properties and compatibility with common organic solvents allow it to be widely applied in laboratories, research institutions, and educational settings.
With its precise color indication, stable performance, and ease of use, Methyl Red remains an important analytical reagent for quality control, chemical testing, and scientific research applications.
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 | 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 |
| 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) |
Product Application of Methyl Red (CAS#493-52-7)
Methyl Red is widely used as an acid-base indicator in analytical chemistry, particularly for titration procedures involving weak bases and ammonia solutions. When prepared as a 0.1% alcoholic solution, it exhibits a clear color transition from red to yellow within the pH range of approximately 4.4 to 6.2, allowing accurate observation of changes in acidity and alkalinity.
Due to its reliable endpoint indication, Methyl Red is suitable for the analysis of ammonia, alkaloids, and other weak organic bases. It is less commonly applied for most organic acid titrations, although it can be used effectively with specific acids such as oxalic acid and picric acid.
Methyl Red may undergo reduction under certain conditions, which can result in color fading; therefore, rapid observation during analytical procedures is recommended. Although newer indicators such as sulfonphthalein-based dyes provide improved stability and sharper color changes in some applications, Methyl Red remains a valuable reagent for laboratory testing, chemical analysis, and educational experiments due to its distinctive color response and established performance.
