Specific Gravity
| Formula / Notation | SG = ρ_substance / ρ_water |
|---|---|
| Also Known As | Relative density, SG, specific weight ratio |
What is Specific Gravity?
Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance (usually water at 4°C for liquids/solids, or air for gases). It is a dimensionless number. If SG > 1, the substance is denser than water and sinks; if SG < 1, it floats. Specific gravity is measured with a hydrometer and is widely used in industrial quality control and chemical analysis.
Formula & Notation
Other Names / Synonyms: Relative density, SG, specific weight ratio
Properties & Characteristics
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance (usually water at 4°C for liquids/solids, or air for gases). It is a dimensionless number. If SG > 1, the substance is denser than water and sinks; if SG < 1, it floats. Specific gravity is measured with a hydrometer and is widely used in industrial quality control and chemical analysis.
Quality control of battery electrolyte (SG indicates charge state). Antifreeze concentration in coolant. Winemaking and brewing (measuring fermentation progress). Petroleum industry (API gravity of crude oil). Acid and base concentration estimation. Urine analysis in clinical medicine.
Measurement concept — safety depends on substance measured. Sulfuric acid (SG = 1.84): highly corrosive. Battery acid: H₂SO₄, corrosive. Hydrometer breakage may release hazardous liquid.
The formula or notation for Specific Gravity is: SG = ρ_substance / ρ_water