Which statement is false about the measurement timing for the filled pycnometer mass?

• A. Absorption will occur as the aggregate soaks in the water; determination of the filled pycnometer mass should be made as quickly as possible, with the measurement obtained no longer than 30 seconds from the introduction of the sample into the water.
• B. Measurement should be taken immediately after submerging the pycnometer.
• C. The mass should be recorded within a minute of submersion.
• D. Measurements can be delayed if the apparatus is busy.

Answer: (A)

Absorption happens as the aggregate soaks in the water, so the mass of the filled pycnometer can change after submersion. To keep that change from skewing the reading, it’s important to weigh the filled pycnometer quickly and with a defined limit. The guidance that the measurement should be obtained within about 30 seconds after the sample is introduced into the water gives a practical, consistent window to minimize the effects of absorption and ensure repeatable results. Weighing immediately after submersion is often impractical or imprecise, while extending the time to a minute or more increases the chance of water uptake altering the mass, and delaying a measurement because the apparatus is busy invites inconsistency. Therefore, measuring within a short, defined window (about 30 seconds) is the best practice.