Determination of Water Content
Laboratory Method
Field Method
Laboratory Method
- Oven Drying Method
- Pycnometer Method
Field Method
- Sand Bath Method
- Alcohol Method
Oven Drying Method
Mass of dry container = M_1
Mass of container + wet soil = M_2
The container consisting of the wet soil is kept in oven for about 24 hours under a temperature of
110 ± 5°C. The period of 24 hours is sufficient for all normal soils to cause evaporation of water from them.
Now, Mass of container + dry soil = M_3
Mass of water (Mw) = M_2 - M_3
Mass of solids (Ms) = M_3 - M_1
Hence, water content of the soil = Mw / Ms
Mass of dry container = M_1
Mass of container + wet soil = M_2
The container consisting of the wet soil is kept in oven for about 24 hours under a temperature of
110 ± 5°C. The period of 24 hours is sufficient for all normal soils to cause evaporation of water from them.
Now, Mass of container + dry soil = M_3
Mass of water (Mw) = M_2 - M_3
Mass of solids (Ms) = M_3 - M_1
Hence, water content of the soil = Mw / Ms
- If the soil contains organic matter, then the temperature of the oven should be in between 60 to 80 degree Centigrade.
Pycnometer Method
Pycnometer is a 500 or 1000 ml capacity glass bottle provided with a conical top. The conical cap has a small hole approximately 5 mm in diameter at its apex. The cap can be screwed onto the glass bottle. To avoid leakage of water, a rubber washer is provided between the conical cap and the rim of the bottle.
To determine water content by this method, the value of G should be known.
This method is suitable for coarse grained soils from which the entrapped air can be easily removed.
This method is suitable for coarse grained soils from which the entrapped air can be easily removed.
Sand Bath Method
Sand Bath Method for the determination of soil water content is a quick field method which is employed when an electric oven is not available for drying of wet soil. Sand is kept on a tray to a height of about 3 cm. A container is filled with wet soil and dried by keeping on the sand bath and heating with stirring. Few white papers are kept on top of the wet soil in the container. The soil is said to be dry when these white papers turn brown. Finally, dry soil is obtained and the water content can be determined with the help of the equation obtained for oven drying method.
Sand Bath Method for the determination of soil water content is a quick field method which is employed when an electric oven is not available for drying of wet soil. Sand is kept on a tray to a height of about 3 cm. A container is filled with wet soil and dried by keeping on the sand bath and heating with stirring. Few white papers are kept on top of the wet soil in the container. The soil is said to be dry when these white papers turn brown. Finally, dry soil is obtained and the water content can be determined with the help of the equation obtained for oven drying method.
Alcohol Method
The wet soil sample is first taken in an evaporating dish. Its mass is determined. Then the sample is mixed with methylated spirit (1 ml for 1 gm of soil). The mixture is made uniform by turning the soil several times with the help of a knife.
The methylated spirit is then burned. The mixture is stirred with a spatula when ignition is taking place. After the spirit is burnt away completely, the dish is allowed to be cooled, and the mass of the dry soil thus obtained is determined. The whole procedure takes about 10 minutes.
The wet soil sample is first taken in an evaporating dish. Its mass is determined. Then the sample is mixed with methylated spirit (1 ml for 1 gm of soil). The mixture is made uniform by turning the soil several times with the help of a knife.
The methylated spirit is then burned. The mixture is stirred with a spatula when ignition is taking place. After the spirit is burnt away completely, the dish is allowed to be cooled, and the mass of the dry soil thus obtained is determined. The whole procedure takes about 10 minutes.