28 - Air Properties T #1 - Posted by Kambiz Ehsani - 5/15/2018

1. Air is a mixture of many gasses and is classified as either Dry or Moist air
2. Dry air contains approx. 78% nitrogen , 20.9% Oxygen, 1% Argon and other gasses (1% other gasses
3. Moist air is a mixture of dry air and water vapor. The amount of moisture present in the mixture may vary from zero to all that air can hold, called its saturation point.
4. If dry air and water vapor were mixed together in a container, the pressure of this mixture is the summation of the pressure exerted by each of the two gasses. This is known as Dalton's Law.
5. Dry air is a gas and follow the gas laws of Charles and Boyle. This gas law states that if air were heated and maintained at a constant pressure, the air would expand and weigh less per cubic foot of volume.This property of air is known as specific density.
6. At sea level, the pressure exerted on the surface of the mercury of 70 degree dry air is 14.696 psi absolute. This will maintain a level of mercury in the tube at 29.92 inches.
7. Specific Density equals one over the specific volume. Or, Specific volume equals one over the specific density. For example, the specific volume of standard air is 13.33 cubic feet per pound, so its density will be one over 13.33 or 0.075 lb per cubic foot.