Which statement about dropper calibration is correct?

• A. It should be calibrated with water only
• B. It can be calibrated with any liquid
• C. It must be calibrated with the liquid to be measured
• D. It should never be calibrated

Answer: (D)

Droppers don’t deliver a fixed volume per drop—the amount released depends on the liquid’s viscosity, surface tension, density, and even the temperature. Because different liquids form drops with different sizes, calibrating with water or with an arbitrary liquid won’t give accurate dosing for a different liquid. Calibrating using the exact liquid you plan to dispense accounts for its specific physical properties, ensuring the measured volume per drop reflects reality under the actual use conditions. Temperature can also shift drop size, so calibration should be done at the working temperature or a closely matched one. Therefore, the best practice is to calibrate with the liquid to be measured to achieve reliable, accurate dosing.