The ratio of the density of a material at a given temperature to the density of an equal volume of water at the same temperature. It is also called relative density and has no units.  Specific gravity describes the weight (mass) of a certain quantity of material. It is useful in determining yield and comparing different materials.

Material and apparatus:

·         Pyknometers

·         Analytical balance

·         Tissue paper

·         Distilled water

Procedures:

·         Accurately weigh clean, dried and empty Pyknometer along with the stopper at room temperature,

·         Fill the Pyknometer with distilled water, Wipe the liquid that spills out using tissue paper, weigh at room temperature and record the weight,

·         Remove the water and fill the Pyknometer with the sample solution to be compared with water to the brim,

·         Insert the stopper gently and Wipe the liquid that spills out using tissue paper,

·         Weight it using analytical balance at room temperature and record the weight,

·         Remove the sample solution and wash it with distilled water;

Calculations:

To calculate the specific gravity of a given solution, use the below formula:

                 Specific gravity:(M₂-M₀)/(M₁-M₀)

                 Where: M₀: mass of empty pyknometer

                               M₁: Mass of pyknometer with distilled water

                               M₂: Mass of pyknometer with sample solution

References

1.      ISO 649-1 Laboratory glassware-density hydrometer for general purpose

2.      (2004). Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement. ASTM Standard D792-00. Vol 81.01. American Society for Testing and Materials. West Conshohocken. PA.

3.      Lange, N. A., Handbook of Chemistry, (Handbook Publishers, Sandusky, 0. 1937).

4.       Damerell, V. R., "A Micro Method for the Determination of Surface Tension and Density," J. Am. Chem. Soc. 49: 2988 (1927).