TD pipets are calibrated with which liquid?

• A. Mercury
• B. Distilled water
• C. Ethanol
• D. Olive oil

Answer: (B)

Pipettes that are calibrated to deliver a specific volume use distilled water as the reference liquid because its density is precisely known at the calibration temperature, making the delivered volume directly linked to a measurable mass. In practice, calibration is often gravimetric: you weigh the amount of water delivered and compare it to the pipette’s nominal volume, using the known density of water at, for example, 20°C to convert mass to volume. Distilled water is chosen because it is nearly pure and has a well-established density, ensuring consistent, reproducible results. Using liquids with different densities, viscosities, or impurities would introduce errors, so water remains the standard.