Aqua Ammonia / Ammonium Hydroxide
NH4OH
- Aqua ammonia, aqueous ammonia and ammonium hydroxide are synonymous terms referring to a solution of ammonia in water.
- Ammonia dissolved in water is present principally as the ion NH4+. Non-ionized molecular NH4OH, sometimes referred to as an associated form of ammonium hydroxide, is also present. Hydrated molecules of NH3 may also exist as NH3 · H20 or NH3 · 2H20.
- Ammonia dissolved in water is commonly referred to as "aqua ammonia".
Grade/Strength of Solution
- The grade or strength of Ammonium Hydroxide usually available commercially is 26-Degree Baumé. However, any strength product can be custom blended to meet the project requirements.
- The Baumé reading refers to a specific gravity scale. A 26-Degree Baumé solution is equivalent to 29.4% by weight of ammonia dissolved in water. Since the Baumé reading varies with temperature, the reading is standardized at 60° F.
Physical Data
- The density of the material compared to water is 0.8974 pounds per cubic foot.
- The freezing point of a 26-Degree Baumé solution is about -112° F.
- Aqua ammonia is corrosive to copper, copper alloys, aluminum alloys and galvanized surfaces.
- An Aqua solution has a vapor pressure that varies with temperature. At ambient temperatures, the vapor pressure of 26-degree Baumé material just about equals atmospheric pressure.
Uses
- Aqua ammonia is an excellent acid neutralizer. Its pH varies with concentration. Typical values are 11.7 at 1%, 12.2 at 5%, 12.4 at 10% and 13.5 at 30%.
- Aqua ammonia is widely used as a reagent in SCR and SNCR systems that is injected in the combustion air to reduce NOx emissions.
- Aqua ammonia is used in many applications instead of anhydrous ammonia to avoid the regulatory threshold limits posed on anhydrous ammonia as an extremely hazardous substance.
Storage & Handling
- Aqua ammonia is shipped and stored in "non-pressurized" containers and is the reason why this is the strongest strength material generally available in the marketplace.
- Aqua should be stored in a closed container and kept cool, otherwise, the ammonia gas will come out of the solution and the material strength will be reduced.