A burette is a laboratory instrument used to precisely measure and dispense a known volume of liquid in titration experiments. Correct usage of a burette is crucial to obtain accurate results. Here’s a step-by-step guide on how to use a burette correctly:
- Burette clamp
- Reagent bottle with the solution
- Beaker or flask for waste
- Analyte solution for titration
- White tile or paper for color change observation (if applicable)
Prepare the Burette:
- Rinse the burette with distilled water and then with the solution to be used, ensuring that the inside of the burette is coated with the solution. This helps prevent dilution and ensures accurate measurements.
Attach the Burette:
- Secure the burette in a burette clamp on a stable stand. The tip of the burette should be positioned just above the beaker or flask where the titration will take place.
Check for Air Bubbles:
- Open the stopcock of the burette slightly to allow any air bubbles to rise to the top. This ensures that the entire column of liquid in the burette is consistent and free of air pockets.
Initial Volume Reading:
- Record the initial volume reading of the burette, typically to two decimal places. Ensure that you read the volume at the bottom of the meniscus (the curve of the liquid surface).
Fill the Burette:
- Using a funnel, carefully pour the solution into the burette until it is above the zero mark. Open the stopcock briefly to allow any remaining air bubbles to escape, then adjust the level to exactly the zero mark by carefully opening or closing the stopcock.
Adjust the Level:
- Use the stopcock to adjust the liquid level to exactly the zero mark. This requires fine control to prevent overfilling or underfilling.
- Slowly open the stopcock to allow the titrant (solution being dispensed) to flow into the receiving container (beaker or flask). During titration, swirl the receiving container to ensure thorough mixing.
End Point Detection:
- As the titration progresses, the titrant’s color may change due to a chemical reaction. If this occurs, you may need to perform the titration over a white tile or paper to better observe the color change. The end point is reached when the color changes, and the receiving solution is neutralized.
Final Volume Reading:
- Record the final volume reading once the color change indicates the end point. Again, read the volume at the bottom of the meniscus.
Calculate Volume Used:
- Subtract the initial volume reading from the final volume reading to determine the volume of titrant used in the titration.
- Use the volume of titrant and the stoichiometry of the reaction to calculate the concentration or quantity of the analyte solution.
- Dispose of waste solutions properly and clean the burette with distilled water after use.
By following these steps carefully, you can effectively and accurately use a burette for titration experiments in the laboratory.