Anhydrous Ammonia storage tanks


  • Anhydrous ammonia is a compound formed by the combination of two (2) gaseous elements, nitrogen and hydrogen.  
  • Ammonia is one (1) part nitrogen to three (3) parts hydrogen. (NH3)
  • Ammonia by weight is fourteen (14) parts nitrogen to three (3) parts hydrogen that is approximately 82% nitrogen to 18% hydrogen.

NH3 Vapor

  • Ammonia appears in nature as a natural substance that results from decomposition.
  • Ammonia vapor is a colorless gas with a pungent odor.
  • Ammonia exists as a vapor at atmospheric conditions.  
  • Ammonia vapor is lighter than air and tends to rise when released to atmosphere. anhydrous ammonia nh3

NH3 Liquid

  • Liquid ammonia released to atmosphere forms a white smoke by freezing the moisture in the air.
  • Liquid ammonia has a very high coefficient of expansion with temperature.
  • One (1) gallon of liquid ammonia weighs approximately 5 lbs; however, the weight varies with temperature.
  • When liquid ammonia reaches a temperature between its melting and critical points, it exerts a vapor pressure that increases with temperature.
  • A closed container of liquid ammonia is in equilibrium with ammonia vapor and the container pressure bears a definite relationship to the temperature.

Physical Data

  • Boiling point is at -28° F.
  • Freezing point is at -107.9° F; a white crystalline mass forms.
  • Critical temperature is at 270.3° F; ammonia exists as a vapor, regardless of pressure above this temperature.
  • Density of ammonia liquid is 42.57 pounds per cubic feet @ -28° F; ammonia liquid is lighter than water.
  • Density of ammonia vapor is .5970 pounds per cubic feet compared to air at atmospheric pressure and @ 32° F.  
  • Volume:  One (1) pound of ammonia vapor occupies a volume of 22.78 cubic feet at 32° F and atmospheric pressure.  One (1) pound of ammonia vapor occupies a volume of 22.5 cubic feet and yields 45 cubic feet of dissociated gas at a ratio of 25% nitrogen and 75% hydrogen @ 70° F and atmospheric pressure.
  • Ammonia begins dissociating into nitrogen and hydrogen at approximately 850° F. anhydrous ammonia nh3

Storage & Handling

  • Ammonia is stored and transported as a liquid under pressure.
  • The pressure on the tank is the liquid pressure and remains the same whether the tank is 10% or 80% full.
  • The maximum filling level of an anhydrous ammonia tank is 85%.
  • Ammonia has a great affinity for water, so special care must be taken to keep the ammonia dry.


  • Anhydrous ammonia is classified by the DOT as a non-flammable gas.
  • Ammonia vapor is flammable over a narrow range of 16% to 25% by volume in air and a strong ignition source must be present.

Compatibilities & Incompatibilities

  • Anhydrous ammonia is compatible with carbon steel and iron.
  • Anhydrous ammonia is not compatible with copper, brass, bronze, zinc or mercury.  Ammonia corrodes copper and brass into a blue-green salt.