The Pycnometer is a tool utilized to determine the specific gravity of both fine-grained and coarse-grained soil particles. This measurement is crucial for calculating various soil properties, such as void ratio and degree of saturation. By using the Pycnometer, researchers can obtain a better understanding of a soil’s characteristics and behavior. This information can be useful in fields such as civil engineering, where soil properties are essential for designing safe and effective structures. Overall, the Pycnometer is a valuable tool for obtaining specific gravity measurements and enhancing our understanding of different soil types.
Specific Gravity of Soil By Pycnometer Method
Equipment for Specific Gravity Test of Soil
In this test, the primary measuring equipment utilized is the Pycnometer. This instrument is comprised of a glass jar with a capacity of one litre, and it is sealed at its top by a brass conical cap. The cap is designed with a screw-type cover, as depicted in figure-1. The Pycnometer is specifically used to measure the density of liquids and solids. It is commonly utilized in various industries, such as the food and beverage industry, pharmaceutical industry, and chemical industry, among others. Its accuracy and reliability make it a valuable tool in ensuring the quality and consistency of products.
Fig.1.Pycnometer Jar of 1litre Capacity
The pycnometer method is commonly used to determine the specific gravity of soil samples. The pycnometer used in this method has a capacity of approximately 1 liter and features a small hole at its apex, measuring 6mm in diameter. To prevent leakage, a washer is placed between the cap and the jar during testing. When closing the jar, it should be screwed up to the mark to maintain a constant volume throughout the test.
To conduct the specific gravity test by the pycnometer method, a number of equipment and apparatus are required. These include a weighing balance with an accuracy of 1g, a glass rod, a vacuum pump, and an oven. The weighing balance is used to accurately measure the weight of the soil sample and the pycnometer, while the glass rod is used to stir the sample and ensure uniformity. The vacuum pump is used to remove any trapped air from the soil sample within the pycnometer, and the oven is used to dry the sample prior to testing. By using these tools and following the proper testing procedures, accurate specific gravity measurements can be obtained for various types of soil samples.
Procedure for Specific Gravity of Soil by Pycnometer Method
To determine the density of soil, a Pycnometer is used in a stepwise process. Firstly, the Pycnometer is cleaned and dried before its mass is measured accurately. To ensure consistency, a mark is made on both the cap and Pycnometer to align them parallel to the axis of the Pycnometer.
About 200 g of oven-dried soil is then placed in the Pycnometer, and its mass is recorded. The cap is removed, and de-aired water is added to the Pycnometer to cover the soil. After screwing the cap back on, the contents are shaken vigorously and connected to a vacuum pump to eliminate entrapped air. The duration of the vacuum pump process is dependent on the texture of the soil, with fine-grained soils requiring about 20 minutes and coarse-grained soils about 10 minutes.
The vacuum pump is then disconnected, and the Pycnometer is filled with water, about three-quarters full. It is reconnected to the vacuum pump for another 5 minutes until air bubbles stop appearing on the surface of the water. The Pycnometer is then filled with water completely up to the mark, and its mass is recorded after drying its exterior. The temperature of the contents is also recorded at this point.
After emptying and cleaning the Pycnometer, it is filled with water only and dried before its mass is measured (M4). This process enables the calculation of the density of the soil.
Fig.2: Specific Gravity of Soil By Pycnometer Method
Observations and Calculations for Specific Gravity of Soil
The given context is a relation used to determine the specific gravity of soil. Specific gravity is a measure of the density of a substance compared to the density of water. In the case of soil, the specific gravity is determined by comparing the weight of a given soil sample to the weight of an equal volume of water.
To calculate the specific gravity of soil, the relation is used. This relation provides a formula or equation that relates the weight of the soil sample to the weight of an equal volume of water. By applying this relation and solving the equation, the specific gravity of the soil can be calculated.
It is important to determine the specific gravity of soil because it can provide useful information about the soil’s physical properties. For example, the specific gravity can be used to calculate the porosity and void ratio of the soil, which are important factors in understanding the soil’s ability to hold water and support structures.
Overall, the given context relates to the determination of the specific gravity of soil, which is an important parameter in understanding the physical properties of soil.
The given context describes a formula involving four variables: M1, M2, M3, and M4, as well as a constant, G, which represents the specific gravity of soils.
To use this formula, one must first determine the values of each of the variables. M1 represents the mass of an empty Pycnometer, which is a container used to measure the density of soil samples. M2 represents the mass of the Pycnometer with dry soil inside, while M3 represents the mass of the Pycnometer with both soil and water. Finally, M4 represents the mass of the Pycnometer filled with water only.
Once these values have been determined, one can use the formula to calculate the specific gravity of the soil, which is represented by the constant G. This calculation involves dividing the difference between M2 and M1 by the difference between M4 and M1, and then subtracting this result from the difference between M3 and M1 divided by the difference between M4 and M1. This final result is then multiplied by the constant G to obtain the specific gravity of the soil.
Overall, this formula provides a way to calculate the specific gravity of soils based on measurements of the masses of various components using a Pycnometer.
Table.1: Observations and Calculations for Specific Gravity of Soil
| 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 | |||
Results of Pycnometer Test
The specific gravity of soil is typically reported at 27 degrees Celsius, unless otherwise specified. The specific gravity values of soil particles generally range between 2.65 and 2.85. Soils containing porous and organic materials will have a specific gravity value of less than 2, while soils containing heavy substances will exhibit a specific gravity value greater than 3.
Precautions
In order to test the specific gravity of a soil sample, it is crucial that the sample be completely free from lumps. If any lumps are present, they must be broken down into their original form to ensure accurate results. Another factor that can contribute to errors in the calculation is the presence of entrapped air. Therefore, it is important to ensure that all entrapped air is completely eliminated before conducting the test.
Additionally, it is essential to check the weighing balance before beginning the test to ensure accuracy. Weighing inaccuracies can also lead to errors in the calculation. Finally, the soil sample that is taken for testing must be completely oven dried. This is necessary to ensure that the sample is in its proper state for testing and to prevent any moisture from interfering with the results. Overall, attention to detail and careful preparation are critical when testing soil samples for specific gravity.