What is specific gravity?

I am trying to determine the specific gravity of polychlorinated biphenyl (PCB). The only information I have is the mass (or volume) of the compound and the molecular weight. What other information do I need to determine the specific gravity? Jason Eardley

	Vocabulary
	density specific gravity

Specific gravity is the density of a substance relative to some reference substance:

Specific gravity = density of substance
density of reference substance

Specific gravity was defined because it's convenient to have a unitless measure of density. The reference substance for solids and liquids is usually water at 4°C. At that temperature, water has a density of 1.0000 g/mL. So if you know the density of a substance in g/mL, for most practical purposes that's numerically equal to the specific gravity.

To find the specific gravity of the PCB, then, you'll need to have the mass (in g) of a given volume (in mL) of PCB.

Author: Fred Senese senese@antoine.frostburg.edu

General Chemistry Online! What is specific gravity?