SPECIFIC GRAVITY OF SOLIDS BY PYCNOMETER METHOD

AIM:

TO DETERMINE SPECIFIC GRAVITY OF SOLIDS BY PYCNOMETER METHOD

Materials and Equipment:

To successfully complete the experiment, the following materials are required:

• about 100g soil and/or sand sieved through a number 4 sieve
• Deaerated, temperature-stabilized water
and the following equipment is required:
• 1500mL volumetric flask (pycnometer) for each sample to be tested
• electronic scale accurate to 0.01g
• number 4 sieve
• catch pan (sieve base)
• 1 ceramic dish for each sample to be tested
• funnel
• small spatula
• hot plate
• freezer (optional, useful for time restraints)
• oven

• access to a sink

Theory:

The Pycnometer method can be used for determination of the specific gravity of solid particles of both fine grained and coarse grained soils. The specific gravity of solids is determined using the relation:

Where M₁=mass of empty Pycnometer,

M₂= mass of the Pycnometer with dry soil

M₃= mass of the Pycnometer and soil and water,

M₄ = mass of Pycnometer filled with water only.

G= Specific gravity of solids.

Equipment:

1. Pycnometer of about 1 litre capacity

2. Weighing balance, with an accuracy of 1g.

3. Glass rod

4. Vacuum pump

Procedure:

1. Clean and dry the Pycnometer. Tightly screw its cap. Take its mass (M₁) to the nearest of 0.1g.

2. Mark the cap and Pycnometer with a vertical line parallel to the axis of the Pycnometer to ensure that the cap is screwed to the same mark each time.

3. Unscrew the cap and place about 200g of oven dried soil in the Pycnometer. Screw the cap. Determine the mass (M₂).

4. Unscrew the cap and add sufficient amount of de-aired water to the Pycnometer so as to cover the soil. Screw on the cap.

5. Shake well the contents. Connect the Pycnometer to a vacuum pump to remove the entrapped air, for about 20 minutes for fine-grained soils and about 10 minutes for coarse-grained soils.

6. Disconnect the vacuum pump. Fill the Pycnometer with water, about three-fourths full. Reapply the vacuum for about 5min till air bubbles stop appearing on the surface of the water.

7. Fill the Pycnometer with water completely upto the mark. Dry it from outside. Take its mass (M₃).

8. Record the temperature of contents.

9. Empty the Pycnometer. Clean tit and wipe it dry.

10. Fill the Pycnometer with water only. Screw on the cap upto the mark. Wipe it dry. Take its mass (M₄).

Observations and calculations:

Sl. No.	Observations an Calculations	Determination No.
		1	2	3
Observation
1	Pycnometer No.
2	Room Temperature
3	Mass of empty Pycnometer (M1)
4	Mass of Pycnometer and dry soil (M2)
5	Mass of Pycnometer, soil and water (M3)
6	Mass of Pycnometer and water (M4)
Calculations
7	M2 – M1
8	M3 – M4
9	Calculate G using formula

RESULT:

Specific gravity of solids at ___⁰C = _____.