What must be done to the tip of a stopcock before performing titration?

Before performing titration, it is essential to fill the tip of the stopcock. This is an important step because it ensures accurate delivery of the titrant into the solution being analyzed. If the tip is not filled, air bubbles can remain, leading to an inaccurate measurement of the volume of the titrant dispensed. These bubbles can affect the end-point determination during titration, compromising the precision of the results.

Filling the tip allows for a smooth and consistent flow of the titrant, which is crucial for achieving a reliable and reproducible outcome in titrations. It also helps to prevent any interruptions in the titration process, which could result from sudden changes in pressure that may occur if the tip were left empty.

Ensuring the tip is properly filled before beginning the titration is a fundamental technique that contributes to the overall accuracy of the analytical procedure.