Question

Given below are two statements :
Statement (I) : International pipette method is regarded as the standard method for particle size analysis due to its accuracy.
Statement (II) : The hydrometer method is rapid but less accurate.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

To remember this:
- Pipette Method: High accuracy, slow/labor-intensive (Standard Reference Method).
- Hydrometer Method: Moderate accuracy, very fast/rapid (Routine Laboratory Method).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Particle-size analysis (mechanical analysis) is the laboratory determination of the size distribution of primary soil particles (sand, silt, clay).
Both the pipette and hydrometer methods are based on Stokes' Law, which describes the sedimentation rate of spherical particles in a viscous fluid.

Step 3: Detailed Explanation:
Let us evaluate both statements individually:
- Statement (I) is true: The International Pipette Method is globally recognized as the standard reference method for particle-size analysis.
It involves taking physical aliquots of a soil suspension at precise depths and times using a pipette.
Because it minimizes mechanical disturbance to the settling column and allows direct gravimetric determination of sediment weights, it provides exceptionally high accuracy and reproducibility.
- Statement (II) is true: The Bouyoucos Hydrometer Method is a rapid, high-throughput alternative.
It measures the density of the soil suspension at specific times using a hydrometer.
While it is much faster and less labor-intensive than the pipette method (requiring no micro-pipetting, drying, or weighing of aliquots), it is considered slightly less accurate because the hydrometer bulb spans a range of depths, disturbing the settling column slightly during measurement.
Therefore, both Statement (I) and Statement (II) are true, matching Option (A).

Step 4: Final Answer:
Both Statement (I) and Statement (II) are true.