Learn the procedure for making a quinaldine red 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.
Quinaldine red (2-(p-Dimethylaminostyryl) quinoline ethiodide) is a colorimetric phosphate detection reagent that is known to be a cationic fluorescent probe for proteins. C21H23IN2 comes in powder form and appears as a dark green compound with a metallic luster however appears purple when dissolved.
It dissolves sparingly soluble in water and freely soluble in ethanol/methanol. Quinaldine Red is used as a cationic fluorescent probe, dyes, metabolites, and an agent in bleaching.
How to prepare quinaldine red indicator for titration:
- Weigh accurately 0.1 gm of quinaldine red and pour it into a 100.00 ml volumetric flask containing 50.00 ml of methanol and swirl until it completely dissolved.
- Once it is dissolved, dilute to 100.00 ml with methanol.
- The concentration of the prepared solution is about 01 gram/liter.
Quinaldine red has pKa values of 2.63, and its pH range is 1.0 to 2.2. Quinaldine red is an indicator that turns from colorless to red throughout the pH range. It is the most commonly used indicator in non-aqueous titrations, acid-base titrations as well as titration of bases with perchloric acid in glacial acetic acid (CH3COOH).
References:
- Wikipedia contributors. (2021, November 8). Quinaldine red. In Wikipedia, The Free Encyclopedia. Available Here:
- Law.resource.org. 2022. [online] Available Here:
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