Glossary / Physical properties
Specific gravity
Specific gravity is the ratio of the density of a liquid or solid to the density of water, with water given a value of 1. A figure below 1 means the material is lighter than water and floats, while a figure above 1 means it is heavier and sinks.
Explanation
Because it is a ratio, specific gravity has no units. It is measured at a stated temperature, since density changes with temperature, and the SDS may name both the material temperature and the water reference temperature. Modern documents increasingly use Relative density, which has the same meaning under GHS.
The practical use is predicting behavior in a spill. Many common solvents and fuels have specific gravity below 1, so they float on water, spread across its surface and can carry burning with them. That makes washing them down a drain a bad idea and can complicate firefighting with water. Materials heavier than water sink to the bottom of puddles, sumps and waterways, where they are harder to recover and can affect aquatic life.
Specific gravity also helps with container handling. It lets you convert between volume and weight, so a drum or tote that looks half full may weigh far more than expected if the product is dense. This matters for lifting, floor loading and shipping.
Do not mix it up with Vapor density, which compares gases with air, or with solubility. A material can float and still dissolve partly in water, so check Solubility in water as well.
What to do and watch for
- Use it to plan spill response: floaters need containment on the surface, sinkers collect low.
- Convert volumes to weights when planning lifting and storage.
- Do not rely on it alone to judge how a chemical will behave in water.
Where it appears on an SDS
- Section 9: Physical and chemical properties. Gives specific gravity or relative density, often with the reference temperature, or notes that it is not available.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.