The density bottle method is used to determine the specific gravity of solid particles, represented by “G.” This value is the ratio of the mass of a given volume of solids to the mass of an equal volume of water at 40°C. Although there are several methods available for determining specific gravity, the density bottle method is the focus here.
Specific Gravity of Solids
Specific gravity is an important parameter for solids, including soil mixes. The specific gravity of a soil mix is determined by the specific gravity values of the different particles within it. The specific gravity of the entire mix can be calculated as the average specific gravity of all solid particles present in the mix. In the case of soils, the specific gravity typically falls within the range of 2.65 to 2.80, and it is a dimensionless quantity. The table below provides average specific gravity values for various types of soils.
| Soil Type | Specific Gravity |
| Gravel | 2.65 – 2.68 |
| Sand | 2.65 – 2.68 |
| Silty sands | 2.66 – 2.70 |
| Silt | 2.66 – 2.70 |
| Inorganic soil | 2.68 – 2.80 |
| Organic Soil | <2.00 |
Fig 1 : Soil Sample
Apparatus Required
To determine the specific gravity of solids using the density bottle method, several apparatus are required. These include a density bottle with a 50 ml capacity, a digital balance with an accuracy of 0.001g, a vacuum desiccator, a vacuum pump, an oven, a constant temperature water bath set to 27°C, and a spatula.
The density bottle is used to measure the volume of the solid, while the digital balance is used to measure its weight. The vacuum desiccator and vacuum pump are used to remove any air bubbles from the sample, and the oven is used to dry the sample. The constant temperature water bath is used to control the temperature of the sample during the experiment. Finally, the spatula is used to transfer the sample from the container to the density bottle.
Overall, these apparatus are essential for accurately determining the specific gravity of solids using the density bottle method.
Fig 2 : Density Bottle
Test Procedure
The procedure for determining the specific gravity of solids using a density bottle involves several steps. Firstly, the density bottle needs to be cleaned and dried by placing it in an oven at a temperature of 105°C to 100°C. Once it has been dried, it should be allowed to cool down by placing it in a desiccator.
The next step is to weigh the density bottle along with its stopper using a balance with an accuracy of 0.001 gm. This weight should be noted down as “M1”. Then, 5 to 10 g of oven-dried sample should be placed in the density bottle and weighed along with the stopper and the dry sample. This weight should be noted down as “M2”.
After weighing the sample, de-aired distilled water should be added to the soil in the density bottle up to the soil level. The bottle should then be shaken gently to mix the soil and water. The stopper should then be removed, and the density bottle should be placed in a vacuum desiccator.
Finally, a vacuum pressure of 55 cm of mercury should be applied to the density bottle for about one hour in the vacuum desiccator. This step helps to expel any air entrapped in the soil, which is necessary for an accurate measurement of the specific gravity of the solids.
Fig 3 : Vacuum Desiccator and Vacuum Pump
To prepare the soil specimen for analysis, the first step is to remove the lid of the bottle and stir the soil using a spatula. The soil that adheres to the spatula is then washed into the bottle with air-free distilled water. After this, vacuum pressure is applied for some time, and this is stopped when no more air is evolved from the specimen. It is also possible to remove any entrapped air by heating the specimen in the absence of a vacuum desiccator. Once the air has been removed, the bottle is removed from the desiccator and more distilled water is added until the bottle is full. The stopper is then inserted.
To ensure a constant temperature throughout the bottle, it is immersed in a water bath for one hour. After this hour has passed, the bottle is taken out of the water bath, and the outside is cleaned and dried using a smooth cloth. The next step is to weigh the bottle, which includes the soil and water, and this weight is noted down as “M3”.
In the final step, the bottle is emptied, washed, and refilled with only distilled water. The bottle is then placed in the water bath for one hour to maintain the same temperature during the experiment. The bottle, now full of distilled water and with the stopper inserted, is weighed again, and this weight is noted down as “M4”. This entire procedure is repeated three times, and the average reading of the three observations is taken as the final result.
Fig 4 : Computation of Specific Gravity
Observations and Calculations
| Observations | 1 | 2 | 3 |
| Mass of empty density bottle (M1) | |||
| Mass of Mass of bottle dry soil (M2) | |||
| Mass of bottle, soil and water (M3) | |||
| Mass of bottle filled with water (M4) | |||
| Specific gravity of solids | |||
| Average specific gravity (G) |
In the laboratory, the specific gravity of solid particles is measured as the ratio of the mass density of the solids to that of water. This measurement is important in various fields such as geology, engineering, and construction. It provides valuable information on the physical properties of the solid materials, which is useful in designing and constructing structures and materials that can withstand specific conditions and environments.
To determine the specific gravity of solid particles, the mass of the solid particles is first measured using a balance. Next, the volume of the solid particles is measured using a device such as a pycnometer or displacement vessel. The volume measurement is done by immersing the solid particles in water and measuring the displacement of water.
Once the mass and volume of the solid particles are known, the specific gravity can be calculated using the following relation:
specific gravity = (mass density of solids) / (mass density of water)
The mass density of the solids can be calculated by dividing the mass of the solids by their volume. The mass density of water is known to be 1000 kg/m³ at standard conditions. Therefore, by substituting the values in the above relation, the specific gravity of the solid particles can be calculated.
Overall, determining the specific gravity of solid particles is a crucial step in understanding their physical properties and behavior. It helps in selecting and designing appropriate materials for specific applications and environments.
The given context involves four masses related to a bottle and its contents. The first mass is denoted by M1 and refers to the mass of the empty bottle. The second mass, denoted by M2, represents the total mass of the bottle and dry soil. The third mass, denoted by M3, is the mass of the bottle, soil, and water. Finally, the fourth mass, denoted by M4, is the mass of the bottle filled with water only.
To summarize, these masses represent the weight of different combinations of the bottle and its contents. M1 is the weight of the empty bottle, while M2 is the weight of the bottle and dry soil. M3 is the weight of the bottle, soil, and water together, and M4 represents the weight of the bottle when it is completely filled with water.
Result
Specific gravity of the given sample = ________.