A dropper must be calibrated with the liquid that will be measured.

• A. True
• B. Sometimes
• C. Not necessary
• D. False

Answer: (A)

Calibration should be done with the liquid that will be measured because the size of each drop from a dropper depends on liquid properties such as surface tension, viscosity, and density. Different liquids wet the dropper tip differently, so the same dropper can produce slightly different drop volumes with different liquids. If you calibrate with water but use the dropper for a different liquid, you’ll get systematic errors in the delivered volume. Calibrating with the actual liquid (and at the expected temperature) accounts for these factors and ensures the volume you dispense matches what you intend. That’s why this practice is the most reliable approach.