Learn the procedure for making a methylene blue indicator solution.
The compound that changes color when exposed to acidic or basic solutions is called an indicator. Color indicators are commonly used to measure pH and are added to the reaction mixture to identify the titration endpoint/equivalence point.
Methylene blue (C16H18ClN3S), also known as methylthioninium chloride, is a photoactive phenothiazine dye. It has 3, 7-bis (dimethylamino) phenothiazine-5-ium as the counterion.
Methylene blue is a heterocyclic aromatic chemical compound that occurs as a dark green crystalline powder with a metallic appearance. It is an oxidation-reduction agent which is soluble in water, ethanol, and ethylene glycol. It's useful in a variety of fields, including biology and chemistry.
How to prepare methylene blue indicator for titration:
- Weigh accurately 15.20 mg of methylene blue and pour it into a 100.00 ml volumetric flask containing 50.00 ml of distilled water and swirl until it completely dissolved.
- Once it is dissolved, dilute to 100.00 ml with distilled water.
- The concentration of the prepared solution is about 0.15 g/L.
Methylene blue has pKa values of 2.6, and 11.2. It’s blue when mixed with an oxidizing agent, while turns colorless when mixed with a reducing agent, Methylene blue changes color since it loses electrons in the presence of oxidizing agents. It is widely used as a redox indicator in analytical chemistry. It is also used as an indicator in a variety of chemical reactions.
References:
- Wikipedia contributors. (2022, February 3). Methylene blue. In Wikipedia, The Free Encyclopedia. Available Here:
- Law.resource.org. 2022. [online] Available Here:
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