For determination of specific gravity of soil solids by pycnometer method.

tools and equipment

  • pycnometer
  • Sieve(4.75mm)
  • Vacuum pump
  • Oven
  • weighing balance
  • glass rod

preparation sample

After receiving the soil sample, it is kept in the oven from 105 to 115. is dried at a temperature of0C for a period of 16 to 24 hours.


  1. Dry the pycnometer and weigh it with its cap (W .)1,
  2. Take about 200 g to 300 g of oven dry clay passing through a 4.75 mm sieve into the pycnometer and weigh again (W)2,
  3. Add water to cover the soil and screw the cap on.
  4. Shake the pycnometer well and connect it to the vacuum pump to remove the trapped air for about 10 to 20 minutes.
  5. After the air is removed, fill the pycnometer with water and weigh it (W.)3,
  6. Wash and clean the pycnometer thoroughly.
  7. Completely fill the cleaned pycnometer with water to the top of it with the cap screw on.
  8. After drying the pycnometer outside, weigh (W .)4,


The specific gravity of soil solid (Gs) is calculated using the following equation.

Soil Specific Gravity 1


woo1= empty weight of pycnometer

woo2= pycnometer weight + oven dry soil

woo3= pycnometer weight + oven dry soil + water

woo4= weight of pycnometer + filled water


The result of the specific gravity test is reported to the nearest two digits after the decimal.

safety precautions

  • The soil grains whose specific gravity is to be determined should be completely dry.
  • If lumps form when the soil dries, they should be broken down to its original size.
  • Inaccuracy in weight and failure to completely eliminate trapped air are the main sources of error. Both should be avoided.

reference standard

IS: 2720 (Part 4) – 1985 – Methods of Soil Testing (Part 4-Analysis of Grain Size)

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.