Common Titration Mistakes

It is important to check that the buret tip securely fits into the barrel of the buret. Over time, the buret tip fitting can become loose to the point where the buret will leak. If this happens, it might be difficult to get an accurate reading while the buret steadily continues to drain. This can cause you to overshoot the end point, and even worse, the tip might fall into the flask if the fitting is loose enough.

Remember that the markings on a buret start at zero from the top and increase going down, which is the opposite from most of your other glassware. This is because a buret dispenses liquids from the tip at the bottom whereas containers like beakers and graduated cylinders are used to pour from the top.

It is important to make sure the stopcock is closed before filling the buret. Otherwise the titrant will spill out into the waste beaker or, worse yet, the bench top.

If a titration overshoots the end point, it is still possible to get valid data without having to start over. Measure a small amount of additional sodium carbonate and record the mass. Rinse the additional sodium carbonate into the flask. Ideally, the indicator should change back to blue. If it remains yellow, measure and add more sodium carbonate (recording the mass each time) until the color changes back to blue. Once the solution is blue, the titration can be continued. As long as the masses of all the samples added to the flask are recorded, it will be possible to calculate the total amount of sodium carbonate reacted in the flask.