What is specific gravity Solid and Water?
=> It is the ratio of unit weight of solid to the unit weight of water at 4 degrees C.(Solid)
=> It is the ratio of unit weight of water at any temperature to the unit weight of water at 4 degrees C.
– A pycnometer is usually used for determining the specific gravity of soil.
– Take a dry sample of soil in a picnometer.
– Fill the pycnometer to it’s half capacity and remove the air contained by sample by heating or by sunction.
– Fill the pycnometer to it’s full capacity with water.
– Take a weight of sample with a pycnometer.
– Again take a weight of pycnometer with water along and make the following calculations….
( Distilled water should be used as far as possible)
fig: Phases of soil.
Let us consider,
Weight of soil = Ws
Weight of pycnometer + soil + water = W1
Weight of pycnometer + water = W2
W1 – W2 = Ws – Weight of equal volume of water as that of soil
or, W1 – W2 = Ws – Vs rw (rw = unit of water)
But from definition,
G= rs(unit weight of solid) / rw ( unit weight of water at ant temp.)
= Ws / ( Vs ro) ro = unit weight of water at 4 deg. C
= Ws / ( Ws – W1 + W2)