By John Brennan | Updated March 24, 2022
The most reliable way to determine when a titration has reached its endpoint is by using a pH indicator. For acid‑base titrations, common indicators such as phenolphthalein or thymol blue change color at a specific pH range. Add a few drops of your chosen indicator before starting the experiment.
Consult the Resources section to match your titration’s pH range with the appropriate indicator. The resource will also show the expected color change once the endpoint is reached.
As you pour the titrant from the burette into the analyte flask, swirl gently to ensure a homogeneous mixture. A uniform solution guarantees that the color shift accurately reflects the overall pH.
Place the flask on a white surface—such as a paper sheet or a Kimwipe—to enhance contrast and make subtle color changes easier to spot.
Pour the titrant in small increments. Adding too quickly can overshoot the endpoint, requiring you to restart the titration. A controlled approach reduces error and improves reproducibility.
Watch for the indicator’s color change. When the new color remains stable for at least 30 seconds, you have reached the endpoint and can record the burette volume.
Start with a quick trial to estimate the volume needed to hit the endpoint. Once you know the approximate range, perform a careful second run—add titrant rapidly until you approach the first trial’s volume, then slow down and add one drop at a time until the color change stabilizes.
