What is methyl red?
Methyl red is also known as p-dimethylaminoazobenzene-o-carboxylic acid; methane red; alkane red. It is an organic compound, dark red crystalline powder, soluble in ethanol and acetic acid, almost insoluble in water. Often used as an acid-base indicator.
The ethanol solution of methyl red can significantly reduce the sensitivity due to the esterification of the carboxyl group after being stored for a long time, and the maximum absorption wavelength is 410nm, which can be used for protozoa living body dyeing and acid-base indicator. It can be combined with bromocresol green and methylene blue to form a mixed indicator to shorten the color range and improve the sensitivity of color change; an adsorption indicator for precipitation titration, such as titrating fluoride ions with thorium nitrate; testing free chlorine, chlorite and other oxidants.
Configuration method and use of methyl red indicator
Configuration of methyl red indicator:
Method 1: Weigh 0.40g methyl red, dissolve in 14.9mL sodium hydroxide solution [c(NaOH)=0.02mol/L], and dilute to 1000mL
Method 2: Methyl red indicator (1g/L) Weigh 0.10g of methyl red, dissolve in ethanol, and dilute to 100ml with ethanol.
Configuration of bromocresol green-methyl red indicator:
0.1% bromocresol green: weigh 0.1g bromocresol green, dissolve in ethanol (95%) and dilute with ethanol to 100ml.
0.2% methyl red: take 0.2g of methyl red, dissolve in ethanol (95%) and dilute to 100ml with ethanol in a ratio of 3:1 to obtain bromocresol green-methyl red indicator.
The use of methyl red indicator
When titrating anhydrous sodium carbonate with hydrochloric acid, a methyl red indicator is often used. At the end of the titration, the solution changes from weakly alkaline to weakly acidic, and the structure of the methyl red indicator changes, and the color changes accordingly. It is also used for protozoan live staining. After long-term preservation of ethanol solution, the sensitivity will be significantly reduced due to the esterification of carboxyl groups; the maximum absorption wavelength is 410nm. Acid-base indicator, pH color change range 4.4 (red) ~ 6.2 (yellow); titrate ammonia, weak organic bases and alkaloids, but not suitable for organic acids other than oxalic acid and picric acid.
Difference Between Methyl Red and Methyl Orange
1. Different in nature
Methyl red is a lustrous purple crystal or brown powder, which is soluble in ethanol and acetic acid, while methyl orange is an orange-yellow scaly crystal or powder, which is insoluble in ethanol.
2. The range of discoloration is different
Methyl orange has a discoloration range of 3.1 to 4.4, while methyl red has a discoloration range of 4.4 to 6.2.
3. The end point of titration is different
When using methyl orange as an indicator to reach the second end point, the color of the solution will turn orange, and when using methyl red as an indicator, the color will turn red. Also, methyl orange will be more accurate and methyl red will be more acidic.
4. Different uses
Methyl orange
Methyl orange is a commonly used indicator for acid-base titration in analytical chemistry, but it is not suitable for titration of organic acid compounds. Its aqueous solution with a concentration of 0.1% has a pH of 3.1 (red) to 4.4 (yellow), and is suitable for titration between strong acid and strong base or weak base. It is also used for spectrophotometric determination of chlorine, Australian and Australian ions, and for biological staining, etc.
Methyl red
Methyl red is one of the commonly used acid-base indicators, the usual concentration is 0.1% ethanol solution, pH 4.4 (red)) to 6.2 (yellow), and it is also used for protozoan living dyeing.
In the end
Finally, methyl red and methyl orange are usually not interchangeable due to their different pH values. But it can be used instead when only testing acid and base. Jinbangch has many years of experience in the manufacture of methyl red, and is very familiar with the application, chemical properties, parameters, etc. of methyl red. If you need to buy methyl red, welcome to contact us.