Question

Hydrometer readings are corrected for:
(A) Temperature correction
(B) Meniscus correction
(C) Dispersing agent correction
(D) Pressure correction
Choose the correct answer from the options given below:

• A. (A) and (B) only.
• B. (C) and (D) only.
• C. (A), (B) and (C) only.
• D. (B), (C) and (D) only.

Hint:

Pressure has no role in a gravity sedimentation based hydrometer test.

Answer 1

The Correct Option is C

Step 1: In the hydrometer method of particle size analysis, the observed reading needs correction for temperature, since the density of the soil suspension and the calibration of the hydrometer change with temperature away from the standard calibration temperature.
Step 2: A meniscus correction is needed because the hydrometer scale is calibrated for reading at the bottom of the meniscus, but the actual reading is taken at the top since the suspension is opaque.
Step 3: A dispersing agent (deflocculating agent) correction is needed because the chemical added to keep particles separated slightly increases the specific gravity of the suspension.
Step 4: Pressure correction has no role in this gravity sedimentation based test, so the correct set is (A), (B) and (C) only, option 3.