Learn the procedure for making a xylenol orange 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.
The chemical reagent xylenol orange (C31H32N2O13S) is commonly employed as a tetra-sodium salt as a metal titration indicator. It will appear red in the titration when used for metal titrations and will turn yellow once it reaches its endpoint. It comes in very dark brown to very dark red metallic or crystalline powder which is soluble in water, and ethanol.
Initially, a small quantity of xylenol orange is added to the cobalt solution, forming a complex with some of the Co2+. The color of the xylenol orange changes as the xylenol orange loses the metal ion. The indicator cannot bind the metal ion as strongly as the complexing agent (EDTA) which is used in the titration.
How to prepare xylenol orange indicator for titration:
- Weigh accurately 0.1 gm of xylenol orange 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 and filter if necessary.
- The concentration of the prepared solution is about 01 gram/liter.
Xylenol orange has pKa values of 2.6, 6.4, 6.5, 10.5, and 12.3. Its pH range is 6.4 to 10.4. In an acidic medium, xylenol orange turns yellow, while in a basic condition, it turns orange-red color. It's a versatile indicator in EDTA titrations in an acidic medium.
References:
- Wikipedia contributors. (2021, October 31). Xylenol orange. In Wikipedia, The Free Encyclopedia. Available Here:
- Law.resource.org. 2022. [online] Available Here:
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