TO DETERMINE THE WATER CONTENT OF THE GIVEN MOIST SOIL SAMPLE USING PYCNOMETER

TITLE:

TO DETERMINE THE WATER CONTENT OF THE GIVEN MOIST SOIL SAMPLE USING PYCNOMETER:

OBJECTIVES:

1. To use the specific gravity to calculate water content of a soil sample.

THEORY:

Water content or moisture content is defined as the ratio of the mass of water to the mass of the dry soil.

Pycnometer method ia a quick method of determining the water content of those soil whose specific gravity is accurately known. Pycnometer is a large size density bottle of about 900 ml capacity. A conical brass cap, having a 6 mm diameter hole at its top is screwed to the open end of the pycnometer. 

 let,

`M_1=`mass of pycnometer (along with cap and washer)

`M_2=` mass of pycnometer+moist soil

`M_3=`mass of pycnometer+soil+water

`M_4=`mass of pycnometer+water

`M_4=M_3-M_S+M_S/G`

`M_4-M_3=M_S(1-1/G)`

`M_.... Show More

TITLE:

TO DETERMINE THE WATER CONTENT OF THE GIVEN MOIST SOIL SAMPLE USING PYCNOMETER:

OBJECTIVES:

1. To use the specific gravity to calculate water content of a soil sample.

THEORY:

Water content or moisture content is defined as the ratio of the mass of water to the mass of the dry soil.

Pycnometer method ia a quick method of determining the water content of those soil whose specific gravity is accurately known. Pycnometer is a large size density bottle of about 900 ml capacity. A conical brass cap, having a 6 mm diameter hole at its top is screwed to the open end of the pycnometer. 

 let,

`M_1=`mass of pycnometer (along with cap and washer)

`M_2=` mass of pycnometer+moist soil

`M_3=`mass of pycnometer+soil+water

`M_4=`mass of pycnometer+water

`M_4=M_3-M_S+M_S/G`

`M_4-M_3=M_S(1-1/G)`

`M_S=(M_3-M_4)*G/(G-1)`

Now, the water content is given by,

`w=M_w/M_s`

`=(M_2-M_1-M_S)/M_S`

`=(M_2-M_1)/M_s-1`

`=(M_2-M_1)/(M_3-M_4)(G-1)/G-1`

This method is suitable for coarse grained soils only.

APPARATUS REQUIRED:

• Pycnometer, 

• balance, 

• Glass rod,

•  water

PROCEDURES:

1. The weight of empty pycnometer along with brass cap and the washer was found out say `M_1`.

2. The pycnometer was then filled with about 200 gram of moist sample of soil and weighted again, say `M_2`.

3. Water was then added in the pycnometer in such a way that it is half full of water. The air in the soil sample was then expelled by heating or by suction. The water was then added to its full capacity and pycnometer was weighed again say `M_3`. 

4. The pycnometer was filled with water only and its weight was determined, say `M_4`.

OBSERVATIONS:

Weight of empty pycnometer,`M_1=0.5041\ kg`

Weight of pycnometer+dry soil,`M_2=0.8437\ kg`

Weight of pycnometer+soil + water,`M_3=1.6729\ kg`

Weight of pycnometer + water,`M_4=1.5451\ kg`

CALCULATIONS:

The specific gravity of solids,G is given by:

`w=(M_2-M_1)/(M_3-M_4)(G-1)/G-1`

`=((0.8437-0.5041)/(1.6729-1.5451)*(2.68-1)/2.68)-1`

`=0.6658`

`=66.58%`

RESULTS:

Thus, the water content of the given soil sample was found to be `66.58%`.

SOURCES OF ERRORS:

1. The water may not be added completely full of pycnometer i.e, constant volume may not be achieved.

2. There may be slight error while observing weight.

PRECAUTIONS:

1. Gap should be properly screwed with washer to avoid any leakage.

2. Weight observation should be taken carefully.

CONCLUSIONS:

Thus,the water content of the given soil sample was determined in the laboratory using pycnometer i.e, constant volume method.