A density bottle, also known as a specific gravity bottle, is a specialized glass container used to determine the density of liquids and solids. Let’s delve into the details of how it works and its application:

1. Purpose and Principle:

   • The specific gravity of solid particles is the ratio of the mass of a given volume of solids to the mass of an equal volume of water at 4°C.
   • It is represented by the symbol “G”.
   • The density bottle method is commonly used to determine the specific gravity of solids.

2. Apparatus Required:

   • Density bottle (50 ml capacity)
   • Digital balance (with an accuracy of 0.001g)
   • Vacuum desiccator
   • Vacuum pump
   • Oven
   • Constant temperature water bath (maintained at 27°C)
   • Spatula

3. Test Procedure:

   1. Cleaning and Drying:

      • Clean the density bottle thoroughly.
      • Place it in an oven at a temperature of 105°C to 100°C for drying.
      • After drying, transfer it to a desiccator to cool down.

   2. Weighing the Density Bottle:

      • Weigh the density bottle along with its stopper using a balance with an accuracy of 0.001g. Note down this reading as “M1”.

   3. Adding Sample:

      • Take 5 to 10g of oven-dried sample material and weigh the bottle along with the stopper and the dry sample. Note this reading as “M2”.

   4. Mixing Soil and Water:

      • Add de-aired distilled water to the soil in the density bottle up to the soil level.
      • Gently shake the bottle to mix the soil and water.

   5. Removing Air Entrapped in Soil:

      • Remove the stopper from the density bottle.
      • Place the bottle in a vacuum desiccator and connect the vacuum pump.
      • Apply vacuum pressure (approximately 55 cm of mercury) for about one hour to expel the air entrapped in the soil.

   6. Washing Soil and Adding More Water:

      • Remove the lid and stir the soil using a spatula.
      • Wash the soil adhering to the spatula into the bottle with air-free distilled water.
      • Apply vacuum pressure again until no more air evolves from the specimen.

   7. Final Steps:

      • Remove the bottle from the desiccator.
      • Add more distilled water until the bottle is full.
      • Insert the stopper.
      • Immerse the bottle in a water bath maintained at a constant temperature of 27°C for one hour.
      • Take out the bottle, clean and dry the outside using a smooth cloth.
      • Weigh the bottle, which now represents the total mass of the bottle, soil, and water.

4. Calculation:

   • Calculate the specific gravity using the formula: [ G = \frac{{M2 - M1}}{{M2 - M1 - W}} ] where:
     • (M1) = Initial mass of the density bottle
     • (M2) = Mass of the bottle with soil and water
     • (W) = Mass of the bottle with water alone