Bayer's reagent is used for testing ………

Answer

**Step-by-Step Solution:**

1. **Understanding Bayer's Reagent**: Bayer's reagent is a solution of potassium permanganate (KMnO4) in a dilute alkaline solution. It is commonly referred to as alkaline KMnO4.

2. **Purpose of Bayer's Reagent**: This reagent is primarily used to test for unsaturation in organic compounds. Unsaturation refers to the presence of double or triple bonds in hydrocarbons, such as alkenes and alkynes.

3. **Testing Process**: When Bayer's reagent is added to an unsaturated compound (like an alkene), the purple color of the reagent indicates its presence.

4. **Observation of Color Change**: Upon reaction with the unsaturated compound, the purple color of the Bayer's reagent changes to brown. This color change signifies that the unsaturation has been oxidized, confirming the presence of double or triple bonds.

5. **Conclusion**: Therefore, Bayer's reagent is used for testing unsaturation in organic compounds, particularly alkenes and alkynes.

---