When the specific gravity of solids is known, which one of the following types of methods is used to determine the water content ?
- APycnometer methodCorrect
- BRapid moisture tester method
- COven-drying method
- DSand-replacement method
Solution
Concept
Pycnometer method for water content
Formula
w = [(M₂ − M₁)/(M₃ − M₄) × (G − 1)/G − 1] × 100
Step-by-step solution
1. In the pycnometer method the mass of the pycnometer filled with soil and water is compared with its mass when filled with water only. 2. The specific gravity of the solids is required to convert this into a water content.
Explanation
The pycnometer method gives a quick water content when G is known. The oven-drying method does not need G.
Why the other options are wrong
Oven-drying and rapid moisture tester do not need G; sand replacement determines density.
Shortcut
G known → pycnometer.
Common mistake
Choosing the oven-drying method.
Correct answer: A) Pycnometer method