Lab Techniques How to do a Manual Titration

Rinse the inside of the Burette Rinse the burette with 2-3 cm 3 of water then with 2-3 cm 3 the solution you are going to use Make sure all inside walls including the tip are rinsed.

Fill the Burette Discard the rinse solution into the sink or a “waste” beaker. Close the stopcock, return the burette to the lab stand and fill with solution.

Take an Initial Reading Make sure your eye is level with the meniscus before taking any readings. meniscus

Reading the Burette Read and record burette measurements with care. Take all readings to 2 decimal places. This burette is reading

What are the readings on these burettes? cm cm cm cm 3

Rinse the Pipette Use the rubber pipette filler to draw cm 3 of the sample into the pipette. Hold the pipette in a vertical position and tilt so the solution contacts all inside surfaces of the pipette. Discard the Rinse Solution.

Pipette a Sample Use the pipette filler to draw solution up into the pipette. The volume should be above the mark. Use your index finger to control the level of the solution in the pipette. When the bottom of the meniscus is at the mark, the volume is correct.

Transfer the Sample Move the filled pipetet to an conical flask. Release your finger and allow the liquid to drain on it’s own. Touch the tip of the pipette to the side of the flask and remove the pipette.

Add an Indicator Add 3-4 drops of indicator to each flask.

Use Proper Titration Techniques Manipulate the burette stopcock with your left hand. Hold and swirl the flask with your right hand. Note: Instructions are for right handed persons. Do the reverse if left handed

Rinse Down the Flask Use small amounts of distilled water to rinse down the sides of the flask from time to time, during the titration.

Aiming for Accuracy As you near the endpoint add burette solution dropwise then a fraction of a drop at a time. To add a fraction of a drop, allow the drop to form on the tip of the burette then rinse it in with dist. Water. Accuracy is how close your value is to the actual or known value.

Precision and Finishing The titration is over when the solution changes colour. This is the “End Point” of the titration. Precision is how close your values are to each other. Aim for 3 samples to be within cm 3 of each other.

The image shows the start and finish of the third titre of a series. Copy and complete the table and calculate the mean titre StartFinish