Specific Gravity?

Question

what is specific gravity? and in what units is it expressed?

Answer 1

Specific gravity is the ratio of the density of the substance versus the density of water. Because the density of water is usually 1g/mL or 1g/cu cm, the ratio is equal to the density of the substance. For example, the density of mercury is 13.6g/mL. So the specific gravity of mercury is 13.6. But because specific gravity is a ratio, it has no units.

A useful number to remember is the density of water, 8.320 lb/gal. Once you know the density of another liquid in g/mL, that's the same as specific gravity. So you multiply the density/specific gravity of the other liquid by 8.320, and you've got the density of the other liquid in lb/gal.

Answer 2

Specific gravity is a very useful idea in tackling physics problems. Since this is specific to the material, you can evaluate whether the material is pure or not after taking its weight and volume.

Answer 3

density of your sample / density of water at 4°C

fyi, the density of water at 4°C = 1 kg / l = 1 g/cm^3

specific gravity is dimensionless.

mercury for example...

density of 5.43 g/cm^3

specific gravity = 5.43 g/cm^3 / 1 g/cm^3 = 5.43

Answer 4

Essentially, it is a measure of density but expressed in relation to water's density. Density is expressed in unit mass per unit volume (e.g. grams per liter).