What is the Specific Gravity of air?

Answer 1

Specific gravity is often defined relative to water, in which case the specific gravity of air is 0.001225. Specific gravity can also be defined relative to the density of air, in which case the specific gravity of air is exactly 1. Specific gravity is often defined relative to water, in which case the specific gravity of air is 0.001225. Specific gravity can also be defined relative to the density of air, in which case the specific gravity of air is exactly 1.

Answer 2

The specific gravity of air is 1 by definition. The specific gravity of any gas is typically defined as its density ratio compared to an equal volume of dry air. The specific gravity of substances other than gasses is defined using distilled water as a reference of value 1.

This convention of using air as a reference for gasses was adopted because of the orders of magnitude of difference between the densities of gases versus most other substances. Using air as a reference allows relative density calculations of gases to be performed with few decimal places.

This can lead to some confusion when trying to compare the relative densities of a gas to a non-gas, since the specific gravities of each are based on different reference values. At sea level and at 60 degrees F, water is 784 times more dense than air. To convert water-based specific gravity values to air-based values (for comparison of the specific gravity of a liquid to a gas, for example), multiply the stated specific gravity by 784. Do the inverse to compare a gas to a liquid or solid.

Answer 3

sg is a density comparison , water bieng 1 (density 1000 kg/m^3)

say iron at 8000 kg/m^3 , sg = 8000/1000 = 8 (eight times density of water)

say air at 1.25 kg /m^3 , sg = 1.25/1000 = 0.00125

Answer 4

At 20 °C , dry air has a density of 1.2041 kg/m3, and water has a density of 998.2071 kg/m3. (Wikipedia)

Specific gravity of air = density of air/density of water =

(1.2041 kg/m3)/(998.2071kg/m3) = 0.0012063

Answer 5

The specific gravity of air is approximately 1. It is often used as the reference point for comparing the specific gravity of other substances.