View source for UAN

{{Short description|Solution of urea and ammonium nitrate in water used as a fertilizer}}
{{otheruses}}
'''UAN''' is a [[Solution (chemistry)|solution]] of [[urea]] and [[ammonium nitrate]] in water used as a [[fertilizer]]. The combination of urea and ammonium nitrate has an extremely low [[critical relative humidity]] (18% at 30 °C) and can therefore only be used in liquid fertilizers. The most commonly used grade of these fertilizer solutions is UAN 32.0.0 (32%N) known as UN32 or UN-32, which consists of 45% [[ammonium nitrate]], 35% [[urea]] and only 20% water. Other grades are UAN 28, UAN 30 and UAN 18.
The solutions are quite corrosive towards mild steel (up to {{convert|0.5|in|cm}} per year on C1010 steel) and are therefore generally equipped with a corrosion inhibitor to protect tanks, pipelines, nozzles, etc. Urea&ndash;ammonium nitrate solutions should not be combined with [[calcium ammonium nitrate]] (CAN-17) or other solutions prepared from [[calcium nitrate]]. A thick, milky-white insoluble precipitate forms that may plug nozzles.

== Physical and chemical characteristics of urea ammonium nitrate solutions==
The solutions contain a remarkably low amount of water and  nevertheless have a low salt-out temperature: 

{| class="wikitable" 
|+ style="font-size: larger;" | '''Physical and Chemical Characteristics of UAN Solutions '''
|-
! Grade, N%
| 28
| 30
| 32     
|-
! Ammonium nitrate (%):
| 40
| 42
| 45
|-
! Urea (%):
| 30
| 33
| 35
|-
! Water (%):
| 30
| 25
| 20
|-
! Specific gravity at 16 °C:
| 1.283
| 1.303
| 1.320
|-
! Salt-out temperature (°C):
| -18
| -10
| -2
<!--
|-
|- 

-->
|}

== See also ==
* [[Urea nitrate]]
* [[Nitrourea]]

==References==
* UNIDO and [[International Fertilizer Development Center]] (1998), ''Fertilizer Manual'', Kluwer Academic Publishers, {{ISBN|0-7923-5032-4}}.
* Simplot [https://techsheets.simplot.com/Plant_Nutrients/Urea_Ammon_Nitrate_Solution_32_0_0.pdf UAN-32 Product Data Sheet]
* Poole Chemical [https://pooleag.com/32-0-0 UAN 32% Solution]
* Tom Dorn, Extension Educator, ''[https://web.archive.org/web/20220203011512/http://lancaster.unl.edu/ag/factsheets/288.pdf  Nitrogen Sources]'' University of Nebraska Fact Sheet 288-01

[[Category:Agricultural chemicals]]
[[Category:Fertilizers]]
[[Category:Nitrogen cycle]]
[[Category:Soil improvers]]